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Nanogenerators are interesting for biomedical applications, with a great potential for electrical stimulation of excitable cells. Piezoelectric ZnO nanosheets present unique properties for tissue engineering. In this study, nanogenerator arrays based on ZnO nanosheets are fabricated on transparent coverslips to analyse the biocompatibility and the electromechanical interaction with two types of muscle cells, smooth and skeletal. Both cell types adhere, proliferate and differentiate on the ZnO nanogenerators. Interestingly, the amount of Zn ions released over time from the nanogenerators does not interfere with cell viability and does not trigger the associated inflammatory response, which is not triggered by the nanogenerators themselves either. The local electric field generated by the electromechanical nanogenerator-cell interaction stimulates smooth muscle cells by increasing cytosolic calcium ions, whereas no stimulation effect is observed on skeletal muscle cells. The random orientation of the ZnO nanogenerators, avoiding an overall action potential aligned along the muscle fibre, is hypothesised to be the cause of the cell-type dependent response. This demonstrates the need of optimizing the nanogenerator morphology, orientation and distribution according to the potential biomedical use. Thus, this study demonstrates the cell-scale stimulation triggered by biocompatible piezoelectric nanogenerators without using an external source on smooth muscle cells, although it remarks the cell type-dependent response.

Introduction: Water contamination from dye effluents from various industrial sources has become a major challenge of the scientific community that is difficult to remediate using orthodox chemical and biological procedures. As such, there is a need for more suitable and cost-effective ways to treat such effluents. The present work describes a green-synthesis approach for preparation of three types of Ni-based oxides as effective catalytic materials to remove environmental pollutants. Metal oxide nanomaterials are cheap, abundant, and ecofriendly earth metals, and thus are promising materials for catalytic applications for environmental detoxification., Methods: An aqueous leaf extract of Prunus persica was used as a reducing agent for the synthesis of NiO, NiO-PdO, and NiO-ZnO nanoparticles (NPs). The leaf extract was treated with each metal-salt precursor based on sol-gel synthesis, and then the final procured NPs were analyzed by spectroscopic techniques for structural and morphological makeup. The pure NPs were further explored for catalytic degradation of hazardous aqueous dye at ambient conditions, instead of following any sophisticated experimental conditions., Results and Discussion: Morphological features revealed the pure formation of NiO, NiO-ZnO, and NiO-PdO NPs of size <100nm, characterized by X-ray diffraction spectroscopy and scanning electron microscopy. Catalytic tests with methyl orange revealed the remediation potential of synthesized material, showing the pseudo-first order kinetics ( R 2 <1) for NiO, NiO-PdO, and NiO-ZnO. NiO-ZnO gave outstanding results both in dark ( R 2 =0.88) and light ( R 2 =0.82) with degradation percentage of 99% (dark) in comparison with the other two catalysts. Moreover, excellent catalyst stability for NiO-ZnO) was observed, even after the fourth cycle, under both light and dark conditions and was separated easily during centrifugation., Conclusion: Although all three materials depicted the degradation potential with good stability, but the NiO-ZnO catalyst was the best catalytic material in the present investigation, with prominent degradation percentage, and can be considered as an efficient catalytic material. Thus, we conclude that P . persica -inspired catalytic material could pave the path toward environmental remediation, alternative clean energy, and other biological applications., Competing Interests: The authors report no conflicts of interest for this work., (© 2020 Zahra et al.)

Background: Artificial synaptic behaviors are necessary to investigate and implement since they are considered to be a new computing mechanism for the analysis of complex brain information. However, flexible and transparent artificial synapse devices based on thin-film transistors (TFTs) still need further research., Purpose: To study the application of flexible and transparent thin-film transistors with nanometer thickness on artificial synapses., Materials and Methods: Here, we report the design and fabrication of flexible and transparent artificial synapse devices based on TFTs with polyethylene terephthalate (PET) as the flexible substrate, indium tin oxide (ITO) as the gate and a polyvinyl alcohol (PVA) grid insulating layer as the gate insulation layer at room temperature., Results: The charge and discharge of the carriers in the flexible and transparent thin-film transistors with nanometer thickness can be used for artificial synaptic behavior., Conclusion: In summary, flexible and transparent thin-film transistors with nanometer thickness can be used as pressure and temperature sensors. Besides, inherent charge transfer characteristics of indium gallium zinc oxide semiconductors have been employed to study the biological synapse-like behaviors, including synaptic plasticity, excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), and long-term memory (LTM). More precisely, the spike rate plasticity (SRDP), one representative synaptic plasticity, has been demonstrated. Such TFTs are interesting for building future neuromorphic systems and provide a possibility to act as fundamental blocks for neuromorphic system applications., Competing Interests: The authors report no conflicts of interest in this work., (© 2020 Dai et al.)

Compared with normal cells, cancer or tumor cells have a specific microenvironment and apparently possess a relatively large amount of ROS/RNS, and their overexpression is one of the important reasons for tumor development and deterioration. Therefore, monitoring the changes of intracellular ROS/RNS can improve the awareness of the clinical manifestations of the disease, which will be beneficial for the early diagnosis of cancer and improving treatment efficiency. Herein, in this study we have exploited and constructed a novel strategy based on the SiC@C nanowire electrode for intracellular electrochemical analysis to monitor ROS levels in cancer or tumor cells. Firstly, the SiC@C nanowire electrode was utilized to detect the intracellular ROS radical changes involved in the relevant biological processes of cancer cells where fluorescent zinc nanoclusters were biosynthesized in situ in target cancer cells by using the intracellular microenvironment and specificity of these cancer cells. By combining a confocal fluorescence microscopy study simultaneously, our observations illustrate that accompanied by the apparent change of the intracellular ROS, these in situ biosynthesized fluorescent nanoclusters gradually accumulate inside the cytosolic area with the increase of the reaction time. Moreover, it is evident that the size of the SiC@C nanoelectrodes can match the single cell dimensions, and its unique high spatial resolution provides the possibility of relevant intracellular molecular detection. These nanoelectrochemical biosensors can be adopted to quantitatively determine the change of the ROS content in target single cells in the relevant biological microenvironment or during the in situ biosynthesis process, and are also beneficial for understanding the related mechanism of some specific biological processes including the in situ synthesis at the single cell level.

We report a novel electrochemical sensor for the sensitive and selective determination of the antipsychotic drug chlorpromazine (CPZ) based on the iron (Fe) nanoparticles-loaded graphene oxide (GO-Fe)/three dimensional (3D) honeycomb-like zinc oxide (ZnO) nanohybrid modified screen printed carbon electrode (SPCE). The 3D hierarchical honeycomb-like ZnO was synthesized using a novel aqueous hydrothermal method and the GO-Fe/ZnO nanohybrid was prepared based on an inexpensive and fast sonochemical method using a high-intensity ultrasonic bath (Delta DC200H, 200 W, 40 KHz). Characterizations including scanning electron microscopy, elemental mapping, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy were carried out as part of this work. The electrocatalytic oxidation behavior of CPZ at various electrodes was investigated using the cyclic voltammetry technique, through which the GO-Fe/ZnO modified SPCE was identified as the best performing electrode. The quantitative determination of CPZ was then performed using the differential pulse voltammetry technique. The as-prepared GO-Fe/ZnO/SPCE sensor exhibited a quick and sensitive response towards the oxidation of CPZ with linear concentration ranges from 0.02 to 172.74 μM and 222.48 to 1047.74 μM. The modified SPCE sensor displayed a low detection limit (LOD) of 0.02 µM and a high sensitivity of 7.56 µA µM -1 cm -2 . The proposed sensor also showed remarkable operational and storage stability, reproducibility, and repeatability. Furthermore, the practicability of the GO-Fe/ZnO/SPCE sensor has been verified with real sample analysis using commercial antipsychotic CPZ tablets and human urine samples, and adequate recovery has been achieved., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The synthesis of metal oxide nanoparticles with the use of plant extract is a promising alternative to the conventional chemical method. This work aimed to synthesize zinc oxide nanoparticles (ZnONPs) using plant extract of chamomile flower (Matricaria chamomilla L.), olive leave (Olea europaea) and red tomato fruit (Lycopersicon esculentum M.). The synthesized ZnONPs were characterized by UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with EDS profile. The XRD studies confirmed the presence of pure crystalline shapes of ZnO nanoparticles. The ZnONPs synthesized by Olea europaea had the least size range of 40.5 to 124.0 nm as revealed by the SEM observation while XRD revealed a dominant average size of 48.2 nm in the sample which is similar to the size distribution analysis obtained from TEM. The antibacterial effect of ZnONPs synthesized by Olea europaea on Xanthomonas oryzae pv. oryzae (Xoo) strain GZ 0003 had an inhibition zone of 2.2 cm at 16.0 µg/ml which was significantly different from ZnONPs synthesized by Matricaria chamomilla and Lycopersicon esculentum. Also, the bacterial growth, biofilm formation, swimming motility and bacterial cell membrane of Xoo strain GZ 0003 were significantly affected by ZnO nanoparticle. Overall, zinc oxide nanoparticles are promising biocontrol agents that can be used to combat bacterial leaf blight diseases of rice.

The establishment of a benign system for the nanoparticle (NPs) synthesis, is a key in nanotechnology for the environmental and health care industries. Therefore, enrichment of novel biological systems for the green synthesis is in significant demand, to lift up these compounds in the biomedical industries. The present work, reports the green synthesis of ZnO NPs, employing a novel thermophile, identified as Bacillus haynesii (GeneBank : MG822851) isolated from the leaf of date palm plant ( Phoenix dactylifera ), as an eco-friendly nanobiofactory. Physiochemical characterization of ZnO NPs (50 ± 5 nm in size), was achieved by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), diffuse reflectance UV-Visible spectroscopy (DR UV-Vis spectroscopy), Thermogravimetry analysis (TGA), scanning electron microscopy (SEM) and transmissiom electron microscopy (TEM). The morphogenesis and antimicrobial activity of synthesized ZnO NPs, was studied by evaluating the minimum inhibitory/bactericidal concentration (MIC&MBC) against Escherchia coli (8 and 16 mg/mL) and Staphylococcus aureus (4 and 8 mg/mL), respectively. The present study encourages the use of B. haynesii for the green synthesis of ZnO NP. To the best of our knowledge, this is the first report on the study of thermophilic, B. haynesii for green synthesis of NPs in general and ZnO NPs in particular.

In this study, we have investigated the structural and optical properties of nanoconjugates (NJs) consisting of phase pure zinc oxide (ZnO) nanoparticles (NPs) with glucose biomolecules. All NJs were fabricated using a standard biochemical synthesis process. Structural, optical, vibrational, and biochemical interface properties of nano-bio composites are probed by different complementary characterization techniques. The XRD patterns of the NPs and NJs illustrate a highly phase pure ZnO structure. A visible green emission in the photoluminescence spectrum, mainly associated with the oxygen vacancies on the surface of ZnO nanostructure, is significantly reduced by the incorporation of glucose biomolecules. The strong binding interaction of glucose biomolecule on the surface of ZnO NPs results in the reduction in green-yellow-orange emission intensities. The interaction of glucose molecules modifies oxygen vacancies by capturing free electrons from the ZnO surface region. Significant changes in the peak intensity and relative peak position of some of the glucose and ZnO NPs in Raman spectra refer to the direct binding between these two nano- and bio-components. In the X-ray photoelectron spectroscopy, the binding energy of O 1s core level in NJs increases from 531 eV (O 1s core level position for ZnO) and the increment is more with higher initial glucose concentration in the solution during synthesis. This study serves as a promising platform for the development of new kinds of NJs and investigation of their interfacial properties which can take the frontier forward for integration and multifunctionality.

Low cost, environmentally friendly and industrial-scale approaches for the synthesis of anti-counterfeiting and antibacterial materials are a challenging task. The current research reports novel and inexpensive approaches for the synthesis of zinc oxide nanostructures (ZnO-NSs) using Mini Submersible Pump (MSP) assisted sonochemical reactors. Zinc oxide nanoleaves (ZnO-NLs) were synthesized using MSP assisted sonochemical mixing reactor at gram-scale (4 g). Zinc oxide nanoparticles (ZnO-NPs) were synthesized using MSP assisted sonochemical flow loop reactor at gram-scale (11.5 g). Synthesized ZnO-NSs were characterized by UV-visible spectroscopy, fluorescence spectroscopy, XRD, FTIR, TGA, BET, FEG-SEM, and FEG-TEM. Bare ZnO-NPs and ZnO-NPs coated cotton fabric showed high antibacterial activity against diseases causing Gram-positive bacteria Staphylococcus aureus. Based on the UV fluorescence property of the ZnO-NLs, invisible security ink was developed for anti-counterfeiting applications. The invisible security ink was tested as a rubber stamp and fountain pen inks which were found to be stable on the various kinds of microporous papers. As compared to our previously reported method, disperser assisted sonochemical approach for ZnO-NLs synthesis; the current approach reduces the cost of equipment used from ∼1700 to 4 USD. Both reactors are designed simply (less complicated), based on an environmentally friendly approach, highly scalable, increases the effectiveness of the sonochemical technique and suitable for industrial applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Recent advances in biotechnology have enabled the generation of antibodies with high affinity for the surfaces of specific inorganic materials. Herein, we report the synthesis of functional materials from multiple nanomaterials by using a small bispecific antibody recombinantly constructed from gold-binding and ZnO-binding antibody fragments. The bispecific antibody-mediated spontaneous linkage of gold and ZnO nanoparticles forms a binary gold-ZnO nanoparticle composite membrane. The relatively low melting point of the gold nanoparticles and the solubility of ZnO in dilute acidic solution then allowed for the bottom-up synthesis of a nanoporous gold membrane by means of a low-energy, low-environmental-load protocol. The nanoporous gold membrane showed high catalytic activity for the reduction of p-nitrophenol to p-aminophenol by sodium borohydride. Here, we show the potential utility of nanoparticle pairing mediated by bispecific antibodies for the bottom-up construction of nanostructured materials from multiple nanomaterials.

Cells sense their environment by transducing mechanical stimuli into biochemical signals. Commonly used tools to study cell mechanosensing provide limited spatial and force resolution. Here, a novel nanowire-based platform for monitoring cell forces is reported. Nanowires are functionalized with ligands for cell immunoreceptors, and they are used to explore the mechanosensitivity of natural killer (NK) cells. In particular, it is found that NK cells apply centripetal forces to nanowires, and that the nanowires stimulate cell contraction. Based on the nanowire deformation, it is calculated that cells apply forces of down to 10 pN, which is the smallest value demonstrated so far by microstructured platforms for cell spreading. Furthermore, the roles of: i) nanowire topography and ii) activating ligands in the cell immune function are studied and it is found that only their combination produces enhanced population of activated NK cells. Thus, a mechanosensing mechanism of NK cells is proposed, by which they integrate biochemical and mechanical stimuli into a decision-making machinery analogous to the AND logic gate, whose output is the immune activation. This work reveals unprecedented mechanical aspects of NK cell immune function and introduces an innovative nanomaterial for studying cellular mechanics with unparalleled spatial and mechanical resolution., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Currently, the evolution of green chemistry in the synthesis of nanoparticles (NPs) with the usage of plants has captivated a great response. In this study, in vitro plantlets and callus of Silybum marianum were exploited as a stabilising agent for the synthesis of zinc oxide (ZnO) NPs using zinc acetate and sodium hydroxide as a substitute for chemical method. The contemporary investigation defines the synthesis of ZnO NPs prepared by chemical and bio-extract-assisted methods. Characterisation techniques such as X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and energy dispersive X-ray were used to confirm the synthesis. Although chemical and bio-assisted methods are suitable choices for NPs synthesis, the bio-assisted green assembly is advantageous due to superior stability. Moreover, this report describes the antibacterial activity of the synthesised NPs against standard strains of Klebsiella pneumonia and Bacillus subtilis .

Zinc oxide (ZnO) and ZnO:Cu nanoparticles (NPs) were synthesized using a rapid, controllable, one-pot and room-temperature pulsed UV-laser assisted method. UV-laser irradiation was used as an effective energy source in order to gain better control over the NPs size and morphology in aqueous media. Parameters effective in laser assisted synthesis of NPs such as irradiation time and laser shot repetition rate were optimized. Photoluminescence (PL) spectra of ZnO NPs showed a broad emission with two trap state peaks located at 442 and 485 nm related to electronic transition from zinc interstitial level (I Zn ) to zinc vacancy level (V Zn ) and electronic transition from conduction band to the oxygen vacancy level (V O ), respectively. For ZnO:Cu NPs, trap state emissions disappeared completely and a copper (Cu)-related emission appeared. PL intensity of Cu-related emission increased with the increase in concentration of Cu 2+ , so that for molar ratio of Cu:Zn 2%, optimal value of PL intensity was obtained. The photocatalytic activity of Cu-doped ZnO revealed 50 and 100% increasement than that of undoped NPs under UV and visible irradiation, respectively. The enhanced photocatalytic activity could be attributed to smaller crystal size, as well as creation of impurity acceptor levels (T 2 ) inside the ZnO energy band gap., (Copyright © 2017 John Wiley & Sons, Ltd.)

Zinc oxide (ZnO), as a material with attractive properties, has attracted great interest worldwide, particularly owing to the implementation of the synthesis of nano-sized particles. High luminescent efficiency, a wide band gap (3.36eV), and a large exciton binding energy (60meV) has triggered intense research on the production of nanoparticles using different synthesis methods and on their future applications. ZnO nanomaterials can be used in industry as nano-optical and nano-electrical devices, in food packaging and in medicine as antimicrobial and antitumor agents. The increasing focus on nano zinc oxide resulted in the invention and development of methods of nanoparticles synthesis. Recently, various approaches including physical, chemical and biological ("green chemistry") have been used to prepare ZnO nanocomposites with different morphologies. The obtained nanoparticles can be characterized with a broad range of analytical methods including dynamic light scattering (DLS), electron microscopy (TEM, SEM), UV-VIS spectroscopy, X-ray diffraction (XRD) or inductively coupled plasma with mass spectrometry (ICP-MS). With these it is possible to obtain information concerning the size, shape and optical properties of nanoparticles. ZnO NPs exhibit attractive antimicrobial properties against bacteria (Gram-positive and Gram-negative) and fungi. Zinc oxide nanocomposites show also selective toxicity toward normal and cancerous cells, which is explained by reactive oxygen formation (ROS). Yet despite the potentially interesting antitumor activity of ZnO nanoparticles, it has been proven that they can be also cytotoxic and genotoxic for multiple types of human cells (i.e. neuronal or epithelial cells). This paper reviews the methods of synthesizing zinc oxide nanocomposites as well as their characteristics, antimicrobial activity and cytotoxicity against normal and tumor cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study investigates the in vivo cytotoxicity of ZnO nanoparticles synthesized at industrial scale with embryonic Zebrafish. Industrial synthesis of ZnO nanoparticles was mimicked at lab scale by high energy ball milling technique by milling bulk ZnO particles for 15 h. Synthesized 7 h and 10 h ZnO nanoparticles showed significant alteration of size, zeta potential and optical properties in comparison to Bulk ZnO. Mortality and hatching rate in Zebrafish embryos were influenced by these alterations. Size and charge dependent effect of ZnO nanoparticles exposure on physiology and development of Zebrafish embryos were evident by malfunctioned organ development and abnormal heartbeat rate. Similar dependency on quenching of ROS due to influential hydrogen bond interaction with glycine residue of Sod1 oxidative stress protein and increased apoptosis were observed in cells. The study revealed the mechanism of cytotoxicity in exposed embryonic Zebrafish as an effect of accumulation and internalization inside cells instigating to generation of hypoxic condition and interference with the normal adaptive stress regulation signaling pathways leading towards enhanced apoptosis. The study revealed hidden size and charge dependent in vivo cytotoxicity mechanism of ZnO nanoparticles in Zebrafish embryos insight of the environmental and clinical importance of attention on industrially synthesized ZnO nanoparticles.

The control of chemical migration from new functionalized food contact materials (FCMs) is a challenge for meeting food safety requirements. The non-intentionally added substances (NIAS) constitute a group of chemicals that are not applied, but may be introduced or formed during the production process of FCMs. This study describes a multi-analytical approach for the evaluation of unknown substances that migrate from FCMs. A case study is presented using a developed polymer consisting of a monolayer film with polylactic acid (PLA), polylimonene (PL) and zinc oxide nanoparticles (ZnO NPs). This approach incorporates the platforms of ICP-MS (inductively coupled plasma mass spectrometry), to determine whether there is transference of ZnO NPs used as antimicrobial agent and, the systems GC-MS and LC-MS (gas / liquid chromatography coupled to a quadrupole orbitrap mass spectrometer) for the characterization of the chemical structure of NIAS using the molecular mass and specific features of mass fragmentation. The screening of unknown compounds comprised retrospective analysis and data processing using both, a mass spectral library and databases, for GC and LC data, respectively. This approach has provided the tentative identification and quantification of seven NIAS, 3 by GC (Tripropylene glycol diacrylate, 10-Heneicosene and α-Tocopherol acetate) and 4 by LC (N,N-Diethyldodecanamide, N-[(9Z)-9-Octadecen-1-yl]acetamide, 1-Palmitoylglycerol and Glycerol stearate). This migration study was carried out according to the standard protocols established by EU regulation for FCMs., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: The use of nanomaterials is constantly increasing in electronics, cosmetics, food additives, and is emerging in advanced biomedical applications such as theranostics, bio-imaging and therapeutics. However their safety raises concerns and requires appropriate methods to analyze their fate in vivo., Scope of Review: In this review, we describe the current knowledge about the toxicity of labile metal (ZnO, CuO and Ag) nanoparticles (NPs) both at the organism and cellular levels, and describe the pathways that are triggered to maintain cellular homeostasis. We also describe advanced elemental imaging approaches to analyze intracellular NP fate. Finally, we open the discussion by presenting recent developments in terms of synthesis and applications of Ag and CuO NPs., Major Conclusions: Labile metal nanoparticles (MeNPs) release metal ions that trigger a cellular response involving biomolecules binding to the ions followed by regulation of the redox balance. In addition, specific mechanisms are set up by the cell in response to physiological ions such as Cu(I) and Zn(II). Among all types of NPs, labile MeNPs induce the strongest inflammatory responses which are most probably due to the combined effects of the NPs and of its released ions. Interestingly, recent developments in imaging technologies enable the intracellular visualization of both the NPs and their ions and promise new insights into nanoparticle fate and toxicity., General Significance: The exponential use of nanotechnologies associated with the difficulties of assessing their impact on health and the environment has prompted scientists to develop novel methodologies to characterize these nanoobjects in a biological context., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Biosensing of NADH on bare electrodes has drawbacks such as high over-potential and poisoning during the oxidation reaction. To overcome this challenge a different approach has been undertaken by incorporating neutral red (NR) in Al doped ZnO (AZO) thin films using one-pot chemical bath deposition (CBD). The surface morphology of the films was hexagonal nanorods along the c-axis, perpendicular to the substrate. The thickness of the thin films were ranging from 400 to 3000nm varying dependent on time of deposition (30 to 150min). The average diameter of the nanorods was larger in the presence of neutral red (NR-AZO) with ~300nm in contrast to its absence (AZO) with ~200nm. The density of the packing of nanorods was dependent on the citrate concentration used during deposition. Control over the dopant concentration in the films was achieved by varying the area of Al foil used in the deposition solution. The selected area diffraction (SAED) and X-ray diffraction (XRD) indicated 002 plane of orientation in the nanorods. FTIR and FT-Raman analysis revealed conserved structure of NR and AZO. Chronoamperometric (CA) analysis showed a sensitivity of 0.45μAcm -2 mM -1 and LoD of 22μM within the range 0.075-4mM of NADH. The biological sensing of NADH was validated by physical adsorption of NAD + dependent-lactate dehydrogenase (LDH) on NR-AZO. CA showed sensitivity of 0.56μAcm -2 mM -1 and LoD for lactate was 27μM in the range of 0.1-1mM of lactate. Further validation with real-time serum sample shows that LDH/NR-AZO correlates with the clinical values. The distinction in this study is that the organic mediator like neutral red has been incorporated into the grain structure of the ZnO thin film whereas other study with the mediators have only attempted surface functionalization. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader., (Copyright © 2017 Elsevier B.V. All rights reserved.)

High sensitivity of pressure/strain sensors is the key to accurately evaluating external mechanical stimuli and could become more important in future generations of human-machine interfaces and artificial skin. Here we report the study of a two-terminal piezotronic transistor based on ZnO twin nanoplatelets (TNPT). Owing to the mirror symmetrical structure of ZnO twin nanplatelet, compressive pressure-induced positive piezoelectric polarization charges created at both metal-semiconductor interfaces can simultaneously lower both Schottky barrier heights and thus significantly modulate the carrier transport. Our device exhibits the highest pressure sensitivity of 1448.08-1677.53 meV/MPa, which is more than ∼20 times larger than the highest value reported previously, and a fast response time of <5 ms. In addition, it can be used as a photodector with an ultrahigh external photoresponsivity of ∼1.45 × 10 4 AW -1 , which is ∼10 5 times larger in magnitude than that of commercial UV photodetectors. The coupling between the mirror symmetrical structure and strong piezotronic effect in ZnO twin nanoplatelets may enable the development of ultrasensitive pressure/strain sensors for various applications such as artificial skin, health monitoring, and adaptive biomedical probes.

Two types of ultrasonic instruments used in dentistry have been compared with a sonochemical horn for the production of copper oxide and zinc oxide nanoparticles. The nanoparticles can be produced from benign reagents using dental instruments as the source of sonochemical enhancement. The process has been operated in resin models of teeth in a preliminary exploration of the potential of the method for enhancing procedures such as root canal surgery. The technique is potentially useful but further work is needed for a full assessment of using in-situ generated nanoparticles as an aid to disinfection during some types of dental surgery., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Solubility is a critical component of physicochemical characterisation of engineered nanomaterials (ENMs) and an important parameter in their risk assessments. Standard testing methodologies are needed to estimate the dissolution behaviour and biodurability (half-life) of ENMs in biological fluids. The effect of pH, particle size and crystal form on dissolution behaviour of zinc metal, ZnO and TiO 2 was investigated using a simple 2 h solubility assay at body temperature (37 °C) and two pH conditions (1.5 and 7) to approximately frame the pH range found in human body fluids. Time series dissolution experiments were then conducted to determine rate constants and half-lives. Dissolution characteristics of investigated ENMs were compared with those of their bulk analogues for both pH conditions. Two crystal forms of TiO 2 were considered: anatase and rutile. For all compounds studied, and at both pH conditions, the short solubility assays and the time series experiments consistently showed that biodurability of the bulk analogues was equal to or greater than biodurability of the corresponding nanomaterials. The results showed that particle size and crystal form of inorganic ENMs were important properties that influenced dissolution behaviour and biodurability. All ENMs and bulk analogues displayed significantly higher solubility at low pH than at neutral pH. In the context of classification and read-across approaches, the pH of the dissolution medium was the key parameter. The main implication is that pH and temperature should be specified in solubility testing when evaluating ENM dissolution in human body fluids, even for preliminary (tier 1) screening.

Application of natural biopolymers for green and safe synthesis of zinc oxide nanoparticles on the textiles is a novel and interesting approach. The present study offers the use of natural biopolymer, Tragacanth gum, as the reducing, stabilizing and binding agent for in-situ synthesis of zinc oxide nanoparticles on the cotton fabric. Ultrasonic irradiation leads to clean and easy synthesis of zinc oxide nanoparticles in short-time at low-temperature. FESEM/EDX, XRD, FT-IR spectroscopy, DSC, photocatalytic activities and antimicrobial assay are used to characterize Tragacanth gum/zinc oxide nanoparticles coated cotton fabric. The analysis confirmed synthesis of star-like zinc oxide nanoparticles with hexagonal wurtzite structure on the cotton fabric with the average particle size of 62nm. The finished cotton fabric showed a good photocatalytic activity on degradation of methylene blue and 100% antimicrobial properties with inhibition zone of 3.3±0.1, 3.1±0.1 and 3.0±0.1mm against Staphylococcus aureus, Escherichia coli and Candida albicans., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Structural design factors of sensor units have been studied in order to enhance the sensitivity of pressure sensors based on utilizing a piezoelectric material for an artificial tactile sensor. In this study, we have primarily demonstrated the effect of a square pattern array design in a pressure sensor using ZnO nanowires. Nanowires grown on the edge of cells can be bent easily because of growth direction, density control, and buckling effect. Since smaller square pattern arrays induce a higher circumference to cell area ratio, if one sensor unit consists of many micro-level square pattern arrays, the design enhances the piezoelectric efficiency and the sensitivity. As a result, 20 μ m×20 μ m cell arrays showed three times higher pressure sensitivity than 250 μ m×250 μ m cell array structures at a pressure range from 4 kPa to 14 kPa. The induced piezoelectric voltage with the same pressure level also increased drastically. Therefore, the square pattern array design is more appropriate for a high-sensitive pressure sensor than a simple one-body cell design for tactile systems, and it has the advantage of better power efficiency, which is also important for artificial tactile systems. This suggested cell array design can be applied to various systems using piezoelectric nanowires.

Green synthesis by using biological agents has been a simple and effective approach for the synthesis of various forms of nanoparticles. The present investigation was intended to synthesis Ag-NPs and ZnO-NPs under photo-condition using the aqueous extracts of two mangrove plants namely Heritiera fomes and Sonneratia apetala and evaluate their potential biomedical applications. The formation of nanoparticles in aqueous solution of H. fomes and S. apetala under exposure to sun light was validated by change in color and formation of monodispersed NPs with a narrow particle size distribution. Fourier transform infrared spectroscopy (FT-IR) reveals the presence of Oxime and other heterocyclic compounds to be the most probable compounds responsible for the reduction and stability of nanoparticles in the solutions. The synthesized NPs displayed moderate free radical scavenging properties. The anti-inflammatory potential of ZnO-NPs was recorded to be comparatively higher than that of Ag-NP with 79% and 69.1% respectively. The Ag-NPs with unique properties of inhibiting α-amylase (91.14% and 89.16%) were found to be significantly high indicating its antidiabetic property. The synthesized NPs showed varied zone of inhibition (9-16mm) against the tested microbial pathogens. The synthesized nanoparticles possess strong biological activities in terms of antioxidant, anti-inflammatory, antidiabetic and antibacterial, potentials which could be utilized in various biological applications by the cosmetic, food and biomedical industries., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Adipose-derived stem cells (ASCs) are typically expanded to acquire large numbers of cells for therapeutic applications. Diverse stimuli such as sphingosylphosphocholine and vitamin C have been used to increase the production yield and regenerative potential of ASCs. In the present study, we hypothesized that ZnO nanorods have promising potential for the enhancement of ASC proliferation. ZnO nanorods were prepared using three different methods: grinding and boiling at low temperature with and without surfactant. The physicochemical properties of the nanorods such as their crystallinity, morphology, size, and solvent compatibility were evaluated, and then, the ability of the synthesized ZnO nanorods to enhance ASC proliferation was investigated. Scanning electron microscopy images of all of the ZnO powders showed rod-shaped nanoflakes with lengths of 200-500 nm. Notably, although ZnO-G produced by the grinding method was well dispersed in ethanol, atomic force microscopy images of dispersions of both ZnO-B from boiling methods and ZnO-G indicated the presence of clusters of ZnO nanorods. In contrast, ZnO-B was freely dispersible in 5% dextrose of water and dimethyl sulfoxide, whereas ZnO-G and ZnO-M, produced by boiling with ethanolamine, were not. All three types of ZnO nanorods increased the proliferation of ASCs in a dose-dependent manner. These results collectively suggest that ZnO nanorods have promising potential for use as an agent for the enhancement of ASC proliferation.

Zinc oxide nanoparticles decorated graphene oxide (ZnO@GO) composite was synthesized by simple solvothermal method where zinc oxide (ZnO) nanoparticles and graphene oxide (GO) were synthesized via simple thermal oxidation and Hummers method, respectively. The obtained materials were thoroughly characterized by various physico-chemical techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Raman spectrum shows the intensity of D to G value was close to one which confirms the obtained GO and ZnO@GO composite possesses moderate graphitization. TEM images shows the ZnO nanoparticles mean size of 15±5nm were dispersed over the wrinkled graphene layers. The photocatalytic performance of ZnO@GO composite on degradation of methylene blue (MB) is investigated and the results show that the GO plays an important role in the enhancement of photocatalytic performance. The synthesized ZnO@GO composite achieves a maximum degradation efficiency of 98.5% in a neutral solution under UV-light irradiation for 15min as compared with pure ZnO (degradation efficiency is 49% after 60min of irradiation) due to the increased light absorption, the reduced charge recombination with the introduction of GO. Moreover, the resulting ZnO@GO composite possesses excellent degradation efficiency as compared to ZnO nanoparticles alone on MB., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The naturally occurring biomolecules present in the plant extracts have been identified to play an active role in the single step formation of nanoparticles with varied morphologies and sizes which is greener and environmentally benign. In the present work, spherical zinc oxide nanoparticles (ZnO NPs) of 2-4nm size were synthesized using aqueous extract of fallen Jacaranda mimosifolia flowers (JMFs), treated as waste. The microwave assisted synthesis was completed successfully within 5min. Thereafter, phase identification, morphology and optical band gap of the synthesized ZnO NPs were done using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and UV-Visible spectroscopy techniques. The composition of JMFs extract was analyzed by gas chromatography-mass spectrometry (GC-MS) and the ZnO NPs confirmation was further explored with fourier transform infrared spectroscopy (FTIR). The GC-MS results confirmed the presence of oleic acid which has high propensity of acting as a reducing and capping agent. The UV-Visible data suggested an optical band gap of 4.03eV for ZnO NPs indicating their small size due to quantum confinement. Further, facet specific adsorption of oleic acid on the surface of ZnO NPs was studied computationally to find out the impact of biomolecules in defining the shape and size of NPs. The viability of gram negative Escherichia coli and gram positive Enterococcus faecium bacteria was found to be 48% and 43%, respectively at high concentration of NPs., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Zinc oxide (ZnO) is well-recognized as a biocompatible multifunctional material with outstanding properties as well as low toxicity and biodegradability. In this work, a simple and versatile technique was developed to prepare highly crystalline ZnO nanorods by introducing egg white to a bio-inspired approach. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern results indicated that the ZnO nanorods have single phase nature with the wurtzite structure. Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) results showed the nanometer dimension of the nanorods. Raman, FTIR, and TGA/DTA analyses revealed the formation of wurtzite ZnO. The antibacterial properties of ZnO nanorods were investigated using both Gram-positive and Gram-negative microorganisms. These studies demonstrate that ZnO nanorods have a wide range of antibacterial activities toward various microorganisms that are commonly found in environmental settings. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity of the ZnO nanorods toward Pseudomonas aeruginosa was stronger than that of Escherichia coli and Staphylococcus aureus. Surprisingly, the antibacterial activity did not require specific UV activation using artificial lamps, rather activation was achieved under ambient lighting conditions. Overall, the experimental results suggest that ZnO nanorods could be developed as antibacterial agents against a wide range of microorganisms to control and prevent the spreading and persistence of bacterial infections. This research introduces a new concept to synthesize ZnO nanorods by using egg white as a biological template for various applications including food science, animal science, biochemistry, microbiology and medicine.

In this study, an in-situ approach was used to synthesise zinc oxide nanoparticles on the surface of cotton fabric. The effect of alkaline pre- and after-treatment and Zn(2+) concentration was studied on the morphological, structural, thermal, photocatalytic, and antibacterial properties of loaded cotton fabrics. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffractometer, thermogravimetric analysis, and attenuated total reflection Fourier transform infrared spectrometer were used to characterise the properties of loaded cotton fabrics. Alkaline after-treatment of cotton fabric presented more dispersed zinc oxide nanoparticles, and an increase in Zn(2+) concentration led to form agglomerated nanoparticles on the surface of cotton fibres. The loaded cotton fabrics with zinc oxide nanoparticles presented an inhibition zone against Staphylococcus aureus and Escherichia coli. In addition, the stain of methylene blue on the surface of loaded samples was degraded after irradiated under visible light.

Stretchability represents a key feature for the emerging world of realistic applications in areas, including wearable gadgets, health monitors, and robotic skins. Many optical and electronic technologies that can respond to large strain deformations have been developed. Laser plays a very important role in our daily life since it was discovered, which is highly desirable for the development of stretchable devices. Herein, stretchable random lasers with tunable coherent loops are designed, fabricated, and demonstrated. To illustrate our working principle, the stretchable random laser is made possible by transferring unique ZnO nanobrushes on top of polydimethylsiloxane (PDMS) elastomer substrate. Apart from the traditional gain material of ZnO nanorods, ZnO nanobrushes were used as optical gain materials so they can serve as scattering centers and provide the Fabry-Perot cavity to enhance laser action. The stretchable PDMS substrate gives the degree of freedom to mechanically tune the coherent loops of the random laser action by changing the density of ZnO nanobrushes. It is found that the number of laser modes increases with increasing external strain applied on the PDMS substrate due to the enhanced possibility for the formation of coherent loops. The device can be stretched by up to 30% strain and subjected to more than 100 cycles without loss in laser action. The result shows a major advance for the further development of man-made smart stretchable devices.

We report on new fabrication methods for a transparent, hierarchical, and patterned electrode comprised of either carbon nanotubes or zinc oxide nanorods. Vertically aligned carbon nanotubes or zinc oxide nanorod arrays were fabricated by either chemical vapor deposition or hydrothermal growth, in combination with photolithography. A transparent conductive graphene layer or zinc oxide seed layer was employed as the transparent electrode. On the patterned surface defined using photoresist, the vertically grown carbon nanotubes or zinc oxides could produce a concentrated electric field under applied DC voltage. This periodic electric field was used to align liquid crystal molecules in localized areas within the optical cell, effectively modulating the refractive index. Depending on the material and morphology of these patterned electrodes, the diffraction efficiency presented different behavior. From this study, we established the relationship between the hierarchical structure of the different electrodes and their efficiency for modulating the refractive index. We believe that this study will pave a new path for future optoelectronic applications.

In this study, N-doped ZnO/TiO2 core-shell nanocomposite was successfully sonosynthesized and sonofabricated on wool fabric through a facile one-step method under ambient pressure and low temperature (75-80°C) as a novel photo-catalyst nanocomposite on textile material. The differences between crystalline phase transformation of conventional and ultrasound synthesized N-ZnO/TiO2 has been compared. The influence of different zinc acetate and titanium isopropoxide precursors in the formation of nanocomposite was studied and optimized through response surface methodology. The photocatalytic activity of the sonofabricated catalyst on the wool fabric surface was evaluated through decomposition of Methylene Blue as a model compound under sunlight irradiation. Also, N-doped ZnO/TiO2 nanocomposite sonosynthesized on wool fabric led to photo bleaching of wool fabric due to decomposition of the naturally occurred pigments under daylight irradiation. Further, yellowness index, antibacterial and antifungal activity against Escherichia coli, Staphylococcus aureus and Candida albicans, cell viability, char residual, alkali solubility, mechanical properties and water drop absorption time on the treated wool fabrics were evaluated. Also, the acid solubility of the synthesized nanopowder obtained from sonobath after treatment was characterized in acetic acid indicating higher acid resistance on N-doped ZnO/TiO2 nanocomposite., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this work, nonmetal/metal dual-doped honeycomb-like N-Ag/ZnO nanocomposites were successfully photo sonosynthesized and sonoimmobilized on wool fabric through a facile one-step method under ambient pressure at low temperature as a novel photo-catalyst nanocomposite on textile material. Introducing nitrogen and silver on the sonoprepared nano ZnO particles led to superior photocatalytic activity. The homogenous distribution of the honeycomb-like nanocomposites on the fiber surface was confirmed by FE-SEM, EDX and X-ray mapping. X-ray diffraction patterns also proved the presence of silver metal with a crystal size of 54Å on the photo sonotreated sample with nonmetal/metal dual-doped honeycomb-like N-Ag/ZnO nanocomposites. The defect analysis based on XPS confirmed the composition of the nanocomposite. Ultraviolet-blocking was examined through reflectance spectra in the range of 200-800 nm showing reasonable transmittance property. The sonoloaded wool sample indicated excellent antibacterial/antifungal properties with low negative effect on human dermal fibroblasts. The role of both zinc acetate and silver nitrate concentration on diverse properties of the fabric was investigated and the optimized conditions introduced using response surface methodology. Finally a superior quality wool fabric with multifunctional properties was introduced for using special clothing in different environment., (Copyright © 2015 Elsevier B.V. All rights reserved.)

An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

We report a simple approach to fabricate zinc oxide (ZnO) nanowire based electricity generators on three-dimensional (3D) graphene networks by utilizing a commercial polyurethane (PU) sponge as a structural template. Here, a 3D network of graphene oxide is deposited from solution on the template and then is chemically reduced. Following steps of ZnO nanowire growth, polydimethylsiloxane (PDMS) backfilling and electrode lamination completes the fabrication processes. When compared to conventional generators with 2D planar geometry, the sponge template provides a 3D structure that has a potential to increase power density per unit area. The modified one-pot ZnO synthesis method allows the whole process to be inexpensive and environmentally benign. The nanogenerator yields an open circuit voltage of ∼0.5 V and short circuit current density of ∼2 μA/cm(2), while the output was found to be consistent after ∼3000 cycles. Finite element analysis of stress distribution showed that external stress is concentrated to deform ZnO nanowires by orders of magnitude compared to surrounding PU and PDMS, in agreement with our experiment. It is shown that the backfilled PDMS plays a crucial role for the stress concentration, which leads to an efficient electricity generation.

Nanoantennas have been fabricated by scaling down traditional antenna designs using nanolithographic techniques and testing them at different optical wavelengths, these particular nanoantennas have shown responses in a broad range of frequencies going from visible wavelengths to the range of the terahertz. Some self-assembled nanostructures exist that exhibit similar shapes and properties to those of traditional antenna structures. In this work the emission and absorption properties of self-assembled nanostructures made of zinc oxide nanorods on silver nanowires, which resemble traditional dipole antennas, were measured and simulated in order to test their antenna performance. These structures show resonant properties in the 10-120 THz range, with the main resonance at 60 THz. The radiation pattern of these nanostructures was also obtained by numerical simulations, and it is shown that it can be tailored to increase or decrease its directivity as a function of the location of the energy source of excitation. Experimental measurements were performed by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) in order to show existing vibrational frequencies at the resonant frequencies of the nanostructures, measurements were made from ~9 to 103 THz and the results were in agreement with the simulations. These characteristics make these metal-semiconductor Ag/ZnO nanostructures useful as self-assembled nanoantennas in applications such as terahertz spectroscopy and sensing at terahertz frequencies.

Cytochromes P450 (CYPs) enzymes are involved in catalyzing the metabolism of various endogenous and exogenous compounds. A rapid analysis of drug metabolism reactions by CYPs is required because they can metabolize 95% of current drugs in drug development and effective therapies. Here, we describe a study of piezotronic-effect enhanced drug metabolism and sensing by utilizing a single ZnO nanowire (ZnO NW) device. Owing to the unique hydrophobic feature of a ZnO NW that provides a desirable "microenvironment" for the immobilization of biomolecules, our device can effectively stimulate the tolbutamide metabolism by decorating a ZnO NW with cytochrome P4502C9/CYPs reductase (CYP2C9/CPR) microsomes. By applying an external compressive strain to the ZnO nanowire, the piezotronic effect, which plays a primary role in tuning the transport behavior of a ZnO NW utilizing the created piezoelectric polarization charges at the local interface, can effectively enhance the performance of the device. A theoretical model is proposed using an energy band diagram to explain the experimental data. This study provides a potential approach to study drug metabolism and trace drug detection based on the piezotronic effect.

Novel side-heating gas sensor based on ZnO nanorod circular arrays was firstly fabricated by hydrothermal treatment assisted with a kind of simple dip-coating technique. The structure and morphologies of ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), respectively. XRD result indicates that the obtained ZnO nanorods have good crystalline with the hexagonal wurtzite structure. SEM result indicates that ZnO nanorod arrays are vertically growth on the surface of ceramic tube of side-heating sensor with controlled diameter and length, narrow size distribution and high orientation. The gas sensing properties of ZnO nanorod circular arrays are also evaluated. Comparative to the sensor based on scattered ZnO nanorods responding to 25 ppm H2, CO, C6H5CH3 and C2H5OH gas, respectively, the sensing values of high orientation gas sensor are generally increased by 5%. This novel sensor has good application promising for the fabrication of cost effective and high performance gas sensors.

Photocatalytic degradation of Congo red was investigated using ZnO-CdS core-shell nano-structure coated on glass by Doctor Blade method in aqueous solution under irradiation. Field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were used for the morphological and structural characterization of ZnO-CdS core-shell nanostructures. XRD results showed diffractions of wurtzite zinc oxide core and wurtzite cadmium sulfide shell. FESEM results showed that nanoparticles are nearly hexagonal with an average diameter of about 50 nm. The effect of catalyst loading, UV-light irradiation time and solution pH on photocatalytic degradation of Congo red was studied and optimized values were obtained. Results showed that the employment of efficient photocatalyst and selection of optimal operational parameters may lead to complete decolorization of dye solutions. It was found that ZnO-CdS core-shell nano-structure is more favorable for the degradation of Congo red compare to pure ZnO or pure CdS due to lower electron hole recombination. The results showed that the photocatalytic degradation rate of Congo red is enhanced with increasing the content of ZnO up to ZnO(0.2 M)/CdS(0.075 M) which is reached 88.0% within 100 min irradiation., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Highly stable piezo-immunoglobulin-biosensing has been realized from a SiO2/ZnO nanowire (NW) nanogenerator (NG) as a self-powered/active biosensor. The piezoelectric output generated by the SiO2/ZnO NW NG can act not only as a power source for driving the device, but also as a sensing signal for detecting immunoglobulin G (IgG). The stability of the device is very high, and the relative standard deviation (RSD) ranges from 1.20% to 4.20%. The limit of detection (LOD) of IgG on the device can reach 5.7 ng mL(-1). The response of the device is in a linear relationship with IgG concentration. The biosensing performance of SiO2/ZnO NWs is much higher than that of bare ZnO NWs. A SiO2 layer uniformly coated on the surface of the ZnO NW acts as the gate insulation layer, which increases mechanical robustness and protects it from the electrical leakages and short circuits. The IgG biomolecules modified on the surface of the SiO2/ZnO NW act as a gate potential, and the field effect can influence the surface electron density of ZnO NWs, which varies the screening effect of free-carriers on the piezoelectric output. The present results demonstrate a feasible approach for a highly stable self-powered/active biosensor.

Limited therapeutic efficiency and severe side effects in patients are two major issues existing in current chemotherapy of cancers in clinic. To design a proper theranostic platform seems thus quite needed to target cancer cells accurately by bioimaging and simultaneously release drugs on demand without premature leakage. A novel ZnO-functionalized upconverting nanotheranostic platform has been fabricated for clear multi-modality bioimaging (upconversion luminescence (UCL), computed tomography (CT), and magnetic resonance imaging (MRI)) and specific pH-triggered on-demand drug release. In our theranostic platform multi-modality imaging provides much more detailed and exact information for cancer diagnosis than single-modality imaging. In addition, ZnO can play the role of a "gatekeeper" to efficiently block the drug in the mesopores of the as-prepared agents until it is dissolved in the acidic environment around tumors to realize sustained release of the drug. More importantly, the biodegradable ZnO, which is non-toxic against normal tissues, endows the as-prepared agents with high therapeutic effectiveness but very low side effects. These findings are of great interests and will inspire us much to develop novel effective imaging-guided on-demand chemotherapies in cancer treatment., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Here we report a fully flexible, foldable nanopatterned wearable triboelectric nanogenerator (WTNG) with high power-generating performance and mechanical robustness. Both a silver (Ag)-coated textile and polydimethylsiloxane (PDMS) nanopatterns based on ZnO nanorod arrays on a Ag-coated textile template were used as active triboelectric materials. A high output voltage and current of about 120 V and 65 μA, respectively, were observed from a nanopatterned PDMS-based WTNG, while an output voltage and current of 30 V and 20 μA were obtained by the non-nanopatterned flat PDMS-based WTNG under the same compressive force of 10 kgf. Furthermore, very high voltage and current outputs with an average value of 170 V and 120 μA, respectively, were obtained from a four-layer-stacked WTNG under the same compressive force. Notably it was found there are no significant differences in the output voltages measured from the multilayer-stacked WTNG over 12 000 cycles, confirming the excellent mechanical durability of WTNGs. Finally, we successfully demonstrated the self-powered operation of light-emitting diodes, a liquid crystal display, and a keyless vehicle entry system only with the output power of our WTNG without any help of external power sources.

Compared to conventional top-down photo-cleavage method, a facile bottom-up ink-combination method to in situ and rapidly achieve water wettability and adhesion transition, with a great contrast on the superamphiphobic TiO2 nanostructured film, is described. Moreover, such combination method is suitable for various kinds of superamphiphobic substrate. Oil-based ink covering or removing changes not only the topographical morphology but also surface chemical composition, and these resultant topographical morphology and composition engineering realize the site-selectively switchable wettability varying from superamphiphobicity to amphiphilicity, and water adhesion between sliding superamphiphobicity and sticky superamphiphobicity in micro-scale. Additionally, positive and negative micro-pattern can be achieved by taking advantage of the inherent photocatalytic property of TiO2 with the assistance of anti-UV light ink mask. Finally, the potential applications of the site-selectively sticky superamphiphobic surface were demonstrated. In a proof-of-concept study, the microdroplet manipulation (storage, moving, mixing, and transfer), specific gas sensing, wettability template for positive and negative ZnO patterning, and site-selective cell immobilization have been demonstrated. This study will give an important input to the field of advanced functional material surfaces with special wettability., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Doped quantum dots (d-dots) can serve as fluorescent biosensors and biolabels for biological applications. Our study describes a synthesis of mercaptopropionic acid (MPA)-capped Mn(2+):ZnSe/ZnO d-dots through a facile, cost-efficient hydrothermal route. The as-prepared water-soluble d-dots exhibit strong emission at ca. 580 nm, with a photoluminescence quantum yield (PLQY) as high as 31%, which is the highest value reported to date for such particles prepared via an aqueous route. They also exhibit upconversion emission when excited at 800 nm. With an overall diameter of around 6.7 nm, the d-dots could gain access to the cell nucleus without any surface decoration, demonstrating their promising broad applications as fluorescent labels.

Yttrium-doped ZnO (YZO) nanorods were synthesized by hydrothermal growth on a quartz substrate with various post-annealing temperatures. To investigate the effects of post-annealing on the optical properties and parameters of the nanorods, X-ray diffractometry (XRD), photoluminescence (PL) measurement, and ultraviolet (UV)-visible spectroscopy were used. From the XRD investigation, the full width at half maximum (FWHM) and the dislocation density of the nanorods was found to increase with an increase in the post-annealing temperature. In the PL spectra, the intensity of the near band edge (NBE) emission peak in the UV region also increases with an increase in the temperature of post-annealing. The deep level emission (DLE) peak in the visible region changes with various post-annealing temperatures, and its intensity increases remarkably with post-annealing at 800 degrees C. In this paper, changes in the optical parameters of the nanorods caused by variation in the behavior of Y during post-annealing was investigated, with properties such as absorption coefficients, refractive indices, and dispersion parameters being obtained from transmittance and reflectance analysis.

Flexible oxide thin-film transistors (Oxide-TFTs) have emerged as next generation transistors because of their applicability in electronic device. In particular, the major driving force behind solution-processed zinc oxide film research is its prospective use in printing for electronics. A low-temperature process to improve the performance of solution-processed n-channel ZnO thin-film transistors (TFTs) fabricated via spin-coating and inkjet-printing is introduced here. ZnO nanoparticles were synthesized using a facile sonochemical method that was slightly modified based on a previously reported method. The influence of the annealing atmosphere on both nanoparticle-based TFT devices fabricated via spin-coating and those created via inkjet printing was investigated. For the inkjet-printed TFTs, the characteristics were improved significantly at an annealing temperature of 150 degrees C. The field effect mobility, V(th), and the on/off current ratios were 3.03 cm2/Vs, -3.3 V, and 10(4), respectively. These results indicate that annealing at 150 degrees C 1 h is sufficient to obtain a mobility (μ(sat)) as high as 3.03 cm2/Vs. Also, the active layer of the solution-based ZnO nanoparticles allowed the production of high-performance TFTs for low-cost, large-area electronics and flexible devices.

Novel photocatalysts i.e., metallic nickel and zinc oxide nanoparticles embedded in the carbon-shell ((Ni-ZnO)@C) have been used for photocatalytic splitting of seawater to generate H2. The (Ni-ZnO)@C core-shell nanoparticles having the Zn/Ni ratios of 0-3 were prepared by carbonization of Ni(2+)- and Zn(2+)-β-cyclodextrin at 673 K for 2 h. To increase the collision frequency of water and photoactive sites within the carbon-shell, Ni and ZnO are partially etched from the (Ni-ZnO)@C core-shell to form yolk-shell nanoparticles with a H2SO4 solution (2N). By X-ray diffraction spectroscopy, mainly Ni and ZnO crystallites are observed in the core- and yolk-shell nanoparticles. The sizes of the Ni and ZnO in the (Ni-ZnO)@C nanoreactors are between 7 and 23 nm in diameters determined by TEM and small angel scattering spectroscopy. Under a 5-h UV-Vis light irradiation, 5.01 μmol/hgcat of H2 are yielded from photocatalytic splitting of seawater effected by (Ni-ZnO)@C nanoreactors., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Efforts have been made to elucidate the origin of d(0) magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites. Specifically, the results of O K-edge scanning transmission X-ray microscopy (STXM) and the corresponding X-ray-absorption near-edge structure (XANES) spectroscopy demonstrated that the impurity (non-stoichiometric) region in ZnO NCs contains a greater defect population than the thick region. The intensity of O K-edge STXM-XANES in the impurity region is more predominant in ZnO NCs than in NWs. The increase in the unoccupied (occupied) density of states at/above (at/below) the conduction-band minimum (valence-band maximum) or the Fermi level is related to the population of defects at the O sites, as revealed by comparing the ZnO NCs to the NWs. The results of O K-edge and Zn L3,2-edge X-ray magnetic circular dichroism demonstrated that the origin of magnetization is attributable to the O 2p orbitals rather than the Zn d orbitals. Further, the local density approximation (LDA) + U verified that vacancies in the form of dangling or unpaired 2p states (due to Zn vacancies) induced a significant local spin moment in the nearest-neighboring O atoms to the defect center, which was determined from the uneven local spin density by analyzing the partial density of states of O 2p in ZnO.

More-efficient charge collection and suppressed trap recombination in colloidal quantum dot (CQD) solar cells is achieved by means of a bulk nano-heterojunction (BNH) structure, in which p-type and n-type materials are blended on the nanometer scale. The improved performance of the BNH devices, compared with that of bilayer devices, is displayed in higher photocurrents and higher open-circuit voltages (resulting from a trap passivation mechanism)., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)