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Nano-ZnO being a pre-dominant constituent in every-day utility products encourages to strive for safety. This study was aimed to fill the knowledge gap concerning on mechanism of nano-ZnO toxicity and develop strategies to curb. Synthesized pristine ZnO nanocrystals (NCs) and doping of Fe and Mn in nano-ZnO was characterized for cytotoxicity, reactive oxygen species (ROS) and biotic dissolution traits in Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterial cells. Zinc ions (Zn2+) dissolution and ROS production found responsible in stating toxicological effects of nano-ZnO in E. coli cells. Over Mn (1.09*1022), doping of metal (Fe) atom (1.1*1022) in ZnO lattice introduces kinetic constraints for the release of Zn2+ ions recovered in bacterial pellet which lowers dissolution rate leading low ROS and lipid peroxidation (LPO), delivers high minimum inhibitory concentration (MIC) in both the bacterial cells. Fe doped ZnO NCs also demonstrate effective protective potential in oxidative challenged bacterial cells, with least effect on growth rate, percentage cell viability, membrane damage and ROS production. Further, hemo-compatible response biocompatibility assessed in human red blood cells shows negligible release of hemoglobin (Hb

In this paper, we have studied the feasibility of developing an Ethyl acetate sensor as a biomarker for early detection of lung cancer in the form of a chemical sensor. For this we report the effect of Ni and Cu doping on the electrochemical characteristics of the SnO2 nanomaterial synthesized by sol-gel method. Formation of composite nanomaterial of undoped/doped SnO2 was confirmed by structural, morphological and elemental characterization and used as matrix for ethyl acetate (EA) chemical sensor in the form of screen-printed electrode (SPE). Conventional electrochemical techniques such as cyclic voltammetry (CV), scan rate studies and impedance spectroscopic studies were conducted for several EA concentration from 1 to 20 ppb prepared in phosphate buffer solution (PBS). CV results shows a well-defined oxidation and reduction peak at different potential with different doping. The estimated sensitivity values for pristine SnO2 is $0.3\mu \text{A}$ /ppb, for NiSnO2 is $2.3~\mu \text{A}$ /ppb and for CuSnO2 is $4.8~\mu \text{A}$ /ppb when estimated over the wider range from 1ppb to 20ppb. Selectivity study was also conducted that showed selective response to EA.

Lung cancer detection includes detection of a pattern formed by multiple volatile organic compounds. An individual material has limited selectivity and hence requires tailoring to improve the selectivity and sensing properties. An electronic nose (e-nose) is a concept/device that can help in achieving selectivity and specificity for multiple volatile organic compounds at the same time by using an array of sensors. In this paper, Co and Ni doping in tin oxide was used to investigate as a sensor material for e-nose development. These were synthesized using a sol–gel method and were characterized for structural, morphological, and elemental assessment using X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy, which indicated the formation of the composite nanomaterial of SnO2. These synthesized materials were then used as a working electrode in the form of a screen-printed electrode to determine 1-propanol and isopropyl alcohol (IPA) sensing characteristics. Electrochemical characterization was done by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. In the case of CV studies, well-defined and distinct redox peaks are observed at different potential values indicating the changes due to the dopants. Ni doping in SnO2 shows the highest sensitivity of 2.99 μA/ppb for isopropyl alcohol and 3.11 for 1-propanol, within the detection range. Furthermore, Co–SnO2 shows selectivity for IPA, while Ni–SnO2 is selective to 1-propanol against all other volatile compounds analyzed.

In this study electrochemical sensors, based on undoped and doped (Cr, Mn, Cu and Zn) SnO2 as a sensing electrode material, were fabricated and used to detect acetone (10–600 ppb) and toluene (1–40 ppb). The sol–gel synthesized nanomaterial was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and Contact angle (CA). Electrochemical sensing characteristics were determined from the Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV) and Electrochemical Impedance Spectroscopic analysis (EIS). The electrochemical results reveal that the sensors’ response to acetone was highest with copper doping whereas in case of toluene sensing zinc dopants showed highest sensitivity. This work demonstrated that acetone and toluene sensing is selective with copper and zinc doping and these doped SnO2 nanomaterials can be used for the formation of array/electronic nose and help in simultaneous detection of acetone and toluene both.

Cu-doped ZnO nanoparticles were used in the form of a screen-printed electrode on a prefabricated gold-plated electrode for electrochemically determining the concentration of nanomolar myoglobin (Mb), a cardiac biomarker. Initially, Cu-doped ZnO nanoparticles were synthesised through the sol gel method by using three Cu-doping concentrations (varying number of Cu atoms). Then, the synthesised material was analysed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and field emission secondary electron microscopy. Analysis revealed a mixed phase of ZnO and CuO, whereas the vibration band in the range of 650-700 cm -1 indicated metal oxide formation. Morphological observation showed uniform-sized spherical particles of approximately 15-20 nm (as nanoparticles) that were evenly distributed, which were also confirmed based on the average particle size estimated using XRD data. The developed electrodes were tested for biomarker concentration from 3 to 15 nM based on cyclic voltammogram and impedance spectroscopic curves, where the redox potential/current/charge transfer resistance changed linearly with Mb and dopant (Cu) concentration. The sensitivity was estimated as 2.13-10.14~μAnM -1 cm -2 with dopant concentration of approximately 0.46 nM as the limit of detection.

Bacterial resistance towards the use of synthetic drugs has created a havoc in the modern era of health sciences. Medicinal plants may pave the way for alternative source of medicines that can overcome bacterial resistance. In this regard, employing three different extraction procedure (Maceration, Decoction and Soxhlet) aqueous extract of Moringa oleifera and Azadirachta indica were prepared and observed for bacterial inhibition and antioxidant properties. Phytochemical screening results revealed the presence of phenols, flavonoids, reducing sugars and saponins. Percentage scavenging activity primarily DPPH assay shows Moringa oleifera Soxhlet 6th (MOS 6th) with the highest percentage scavenging activity. Similarly, total flavonoid content estimation results rendered Moringa oleifera Decoction (MOD) as the highest flavonoid containing sample (68.97 ± 0.9) mg RUE/ml. Antibacterial efficiency of the extracts was monitored against Streptococcus mutans (gram-positive) and Escherichia coli (E. Coli) DH5 (gram-negative) bacteria, 96-well microtiter two-fold dilution reveals lowest MIC of 625 μg ml–1 for Neem soxhlet 6th cycle (NS 6th) against Streptococcus mutans while Moringa oliefera soxhelt 2nd cycle shows a low toxicity pattern (MIC 5000 μg ml–1). However, only three extract (Neem Soxhlet 2nd cycle, Moringa oleifera Soxhlet 2nd cycle and Neem Soxhlet 6th cycle) shows inhibitory potential against E. coli. Furthermore, zone of inhibition acquired via agar-well diffusion assay well corroborates with the results of 96-well pate. Based on extraction procedure, Soxhlet method establishes a good toxicity profile against the studied organism.

Nanostructured cerium oxide (CNP) was synthesized via co-precipitation and used as a base matrix to construct an enzyme-less electrochemical sensing platform for a non-electroactive analyte (i.e., melamine in the presence of ascorbic acid (AA)). CeO2 was screen printed (SP) on prefabricated gold electrodes for the indirect detection of melamine. The melamine concentrations varied in the range of 0.01 ppb to 10 ppm with a fixed amount of ascorbic acid (i.e., 50 ppm). Absorption spectra were obtained from 220 to 400 nm for all melamine concentrations. The cyclic voltammogram (CV) for different melamine concentrations was obtained in the applied voltage range of –1 to +1 V. The peak oxidation current reduced as a function of increased melamine concentration in the presence of ascorbic acid, which was supported by absorption studies. The obtained melamine sensitivities were 64.9 and 80.8 μA/ppb/mm2, respectively, without and with ascorbic acid. The limits of detection estimated from three times the signal-to-noise ratio were 1.5 × 10–3 and 2.4 × 10–3 ppb, which are the lowest values so far reported to the best of our knowledge. The electrochemical impedance study predicted the increase of the charge transfer characteristics in the presence of AA, which comprehensively correlated with the CV data. The developed sensor can be used for the detection of melamine in milk, dairy products, and other food items.

An enduring and formidable challenge in nanozyme catalysis is low sensitivity and operational instability, which impedes their biological usage. In this contribution fluorite-structured cerium oxide nanocrystals (CeO2 NCs) with ∼23.04% Ce3+ fraction were found to possess recyclable (10 cycles) peroxidase (POD)-like activity capable of catalyzing the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) when hydrogen peroxide (H2O2) serves as oxidant, and exhibit high substrate affinity under acidic conditions. We tuned this catalytic activity at neutral pH (7.4) using adenosine triphosphate (ATP). It was found that ATP stabilizes the oxidation product and improves catalytic performance at neutral pH. Mechanistic investigation reveals that oxidation of TMB originates from catalyst (CeO2 NCs)-directed decomposition of H2O2, which pools hydroxyl (˙OH) radicals under acidic and neutral environments; kinetic studies indicate a Michaelis–Menten enzyme kinetic model. Notably, above pH 4.5, ATP facilitates a drop in catalyst Km values of about 2.5 and 4.79 times for TMB and H2O2, respectively, suggesting high affinity favouring reaction feasibility at neutral pH. Screening of other relevant modulators shows the following order in promoting catalysis at neutral pH: ATP > histidine ≥ ADP >AMP. This pH-tunable POD-mimic CeO2 nanozyme realizes a nanocatalytic strategy for sourcing ˙OH radicals, which contributes to anti-bacterial performance. This study provides new insight for designing nanozymes and expanding the use of nanozymes in biomedicine.

Mn-doped ZnO nanostructures were synthesized with three different estimated Mn concentration (atoms/cm3) using sol-gel technique. As synthesized nanostructures were analyzed using X-ray diffraction spectroscopy (XRD), Fourier-transform-infrared spectroscopy (FTIR), and field-emission secondary electron microscopy (FE-SEM). XRD pattern reveals of doped ZnO nanostructures reveal a peak related to Zn2Mn3O8 phase along with peaks related to pure ZnO. Average particle size, estimated using Scherer formula, increases with Mn-doping. FE-SEM reveals morphological change from spherical particles (~15-20 nm) to nano-rods then nano-belt like 2 D super lattice structure after doping. Optical band gap obtain from Tauc's plot is 3.82, 2.05, 2.1 and 2.47 eV for pure-ZnO and Mn-doped samples with 13×1017, 20×1017 and 32×1017 Mn atoms/cm3, respectively. Presence of vibration band from 665 to 680 cm-1 in FTIR spectra endorses metal oxide formation. Nanomaterials were screen printed over working electrode of pre-fabricated three terminal electrode. This was used for electrochemical detection of myoglobin (Mb); a biomarker for acute myocardial infarction and were tested for Mb concentrations from 0-15 nM using cyclic voltammetry and electrochemical impedance spectroscopy. Redox current and charge transfer resistance varied linearly with Mb concentration. 7-fold increased sensitivity towards Mb in Mn-doped ZnO sensors is attributed to doping induced stress in nanostructures. Maximum sensitivity of 95μA-cm-2 nM-1 with LOD of 0.35 nM is observed for ZnO with 13 × 1017 Mn atomic/cm3. Response time of ~10 ms is observed. Interference carried out with 7 nM Cytochrome c and 5 mM HSA reveal different oxidation potential and current value for Mb.

A label free electrochemical sensor based on pure titanium oxide and manganese (Mn)-doped titanium oxide (TiO2) nanoparticles are fabricated and characterized for the sensitive detection of myoglobin (Mb) levels to analyze the cardiovascular infarction. Pristine and Mn-doped TiO2 nanoparticles were synthesized via the sol-gel method and characterized in order to understand their structure, morphologies, composition and optical properties. The structural properties revealed that the pure- and doped-TiO2 nanoparticles possess different TiO2 planes. FTIR studies confirm the formation of metal oxide nanoparticles by exhibiting a well-defined peak in the range of 600–650 cm−1. The values of the optical band gap, estimated from UV-Vis spectroscopy, are decreased for the Mn-doped TiO2 nanoparticles. UV-Vis spectra in the presence of myoglobin (Mb) indicated interaction between the TiO2 nanoparticles and myoglobin. The SPE electrodes were then fabricated by printing powder film over the working electrode and tested for label-free electrochemical detection of myoglobin (Mb) in the concentration range of 0–15 nM Mb. The fabricated electrochemical sensor exhibited a high sensitivity of 100.40 μA-cm−2/nM with a lowest detection limit of 0.013 nM (0.22 ng/mL) and a response time of ≤10 ms for sample S3. An interference study with cyt-c and Human Serum Albumin (HSA) of the sensors show the selective response towards Mb in 1:1 mixture.

The capability of functional logic operations is highly intriguing, but far from being realized owing to limited recognition element (RE) and complex readout signals, which limit their applications. In this contribution, for a visual colorimetric sensor for melamine (MEL) we described the construction of two- and three-input AND logic gate by exploiting the intrinsic peroxidase (POD)-like activity of CeO2 nanorods (NRs) (~23.04% Ce3+ fraction and aspect ratio (RTEM) of 3.85 ± 0.18) as RE at acidic pH (4.5). Further ATP piloted catalytic tuning of POD-like activity in CeO2 NRs employed for a functional logic gate-controlled MEL sensing at neutral pH (7.4). AND logic circuit operated MEL sensing record colorimetric response time of 15 minutes to produce blue color proportionate to MEL concentration. The fabricated nanozyme (CeO2)-based logic gate sensor probe for MEL at pH 4.5 showed a linear response from 0.004 nM to 1.56 nM with a limit of detection (LOD) of 4 pM, while translation from acidic to neutral pH (at 7.4) sensor exhibited linear response ranging from 0.2 nM to 3.12 nM with a LOD value of 17 pM. Through CeO2 POD-like nanozyme behavior under acidic and neutral pH, the fabricated logic gate sensor showed high affinity for MEL, generating prominent visual output with picomolar sensitivity, good reproducibility, and stability with relative standard deviation (RSD) &lt, 1% and 2%, respectively. A feasibility study in real samples (raw milk and milk powder) showed good recoveries with negligible matrix effect, an anti-interference experiment revealed sensor selectivity, highlighting robust sensor practical utility. With the merits of high sensitivity, specificity, low cost, and simplified sample processing, the developed logic-controlled colorimetric MEL sensing platform with appropriate modifications can be recognized as a potent methodology for on-site analysis of various food adulterants and related applications.

The sensitive and selective electrochemical detection of picric acid (PA), a toxic, harmful environmental pollutant and an explosive, using different morphologies of cuprous oxide (Cu2O) is reported. The different Cu2O morphologies, synthesized by a hydrothermal method for 8 h, 10 h, and 12 h, were characterized using various techniques to confirm their morphological, optical, compositional, and structural properties. Sensors, fabricated in the form of screen-printed electrodes using these different morphologies of Cu2O, were used to study the electrochemical sensing capabilities of the nanomaterials for PA (7.8 μ M to 10.0 mM). Cyclic voltammetry studies revealed a distinct change in the redox peak current as a function of PA concentration, which was further confirmed by electrochemical impedance spectroscopy studies, as the charge-transfer resistance increased with an increase in PA concentration. Scan rate studies showed that the electrochemical sensing of PA is a surface-controlled process, involving rapid electron transfer. Among the different morphologies, Cu2O synthesized for 8 h showed a reproducible and reliable sensitivity of 130.4 μA mM−1 cm−2 with a limit of detection of 39 μM and good linearity over a wide range of PA concentrations. Interference studies with other phenolic compounds revealed the presence of distinct peaks corresponding to PA, indicating that the fabricated sensor shows specificity and selectivity for PA.

In a quest for developing new material with performance of dye sensitized solar cells (DSSC) a non-metallic doping i.e., of nitrogen was carried out to commercial TiO2 nanoparticle using simple, facile and sustainable mechanochemistry method. Melamine was used as source of nitrogen and different weight percentages (10, 30, 50, 70 and 90%), mixed with TiO2 mechanically in a ball mill for 12 h at an speed of 500 rotations per minute followed by annealing at 550 °C for 2 h under constant N2 flow. The post nitrogen doping structural analysis indicated anatase phase of TiO2.The morphological observations by transmission electron microscopy did not show change due to melamine and particle size remains less than 30 nm. N-doping resulted in an increased wavelength of peak absorption from 334 nm to about 350 nm and shifting of absorption edge from UV (~ 400 nm) to visible region (~ 500 nm) resulting in the reduction of the band gap from 3.14 to 2.43 eV which is supported by XPS and Tauc plot analysis. The functional analysis reveals amide bond at higher melamine concentration. The DSSC characteristics were measured with source-meter coupled with simulated light source which shows a significant increase of cell efficiency from 26 with 10% of melamine to that of 86 with 90% melamine. The increase in efficiency was linear with increasing nitrogen doping concentration. The study suggested that melamine can be used as a suitable N-dopant source for improved photoconversion properties that can help engineer to develop a device with enhanced performance.

Here we report development of a hydroquinone (HQ) electrochemical sensor using nanosized manganese doped titanium oxide as a composite material. The nanomaterial was synthesized with sol gel method using calculated amount of Mn and Ti atoms resulting into a composite metal oxide. Morphological observations indicated a uniform particle size and shape distribution with almost spherical shape and size of about 20–30 nm. While structural analysis indicated formation of mixed phase of TiO₂ and MnO forming MnTiO₃. The synthesized nanomaterial was used as a matrix for fabrication of hydroquinone electrochemical sensor and tested over a wide range from 2 mM to 10 mM. The developed electrochemical sensor exhibited sensitivity of 2.96 μA mM⁻¹ (23.55 μA mM⁻¹ cm⁻²) with a detection limit of 7.5 μM, which is rarely reported for such composite nanomaterial.

Extensive research have been made in improving the dye sensitized solar cells (DSSC) performance by designing, tailoring and enhancing the photoconversion properties of the matrix. The approaches used are material synthesis, dye permutation combinations, use of natural extracts or using several sensitizers. The polymers are also being explored in this regards in their pristine or composite forms. Therefore, in this study an attempt is made to synthesize a mesoporous polyaniline–titanium dioxide (PANI–TiO2) nanocomposites with one pot synthesis approach at different concentrations of PANI (0.3–0.7 ml). Titanium isopropoxide was used as precursor for TiO2 with aniline and the material was synthesized at ice bath temperature. Morphological observations showed that the composite is a mesoporous material with tubular structure where TiO2 particles are seen entrapped in the polymer matrix and found that intercalation can be tailored with PANI concentration. Structural, functional and optical characterization indicate anatase phase of TiO2, with several functional bands that can help in dye interaction and broad absorption bands within visible region. The photocurrent-voltage response was measured with simulated light and source-meter. It is interesting to note that increasing PANI concentration enhances the mesoporous structure and hence increases the dye loading capacity and photoconductivity of the material. The efficiency increased by about 22 % with addition of 0.5 ml of PANI from 0.3 ml. The proposed study has indicated that such material have the potential to be used for DSSC fabrication with which the device performance can further be increased to a better levels.

Here we report a simple and effective method in tailoring the optoelectronic properties of semi-conducting metal oxide for suitable device application. Sol-gel synthesis was used to synthesize manganese doped TiO2 nanopowder and commercially available TiO2 nanopowder was used as reference material. Thick films of these powder were screen printed on FTO coated glass and annealed at 450 degrees C in ambient air. Separately, 60 μL of neodymium chloride prepared from neodymium oxide, 60 μL of ruthenium based commercial dye (N719) and 60 μL of extracts of calendula orange and dog flower were used as sensitizer to improve the photoconductance properties. Elemental analysis confirmed synthesis of composite material of Mn and TiO2. Morphological observation showed a uniform particles of 25 to 50 nm diameter. Optoelectronic properties were studied by using thick films of these powders as working electrode as a function of wavelength from 430 to 750 nm and the cyclic voltammogram were obtained by scanning potential from -1.5 V to +1.5 V at the illumination intensity of 1000 Wm(-2). Sensitization resulted in additional absorption and functional bands. Oxidation peak current was found decreasing with increasing wavelength. Sensitization with flower extract resulted in increased oxidation current at higher wavelength indicating the improved photoconduction in comparison with N719 and neodymium.

To elucidate the effect of zinc oxide nanoparticles (ZnO-NPs) with different surface modifications in relieving the oxidative stress in cultured human embryonic kidney cells (HEK-293) following investigation was performed. Oxidative stress was artificially induced by hydrogen peroxide in HEK-293 cell culture and its management was studied. Alkyl amines modified ZnO-NPs with curcumin and reduced glutathione (GSH) functionalization was used in managing oxidative stress and had shown promising results. ZnO-NPs used in this study were synthesized via non-aqueous sol-gel method and FESEM characterisation showed them of spherical shape of about 20-50 nm size with amine, curcumin and GSH functionalization. UV-visible and FTIR spectroscopic characterizations confirmed functionalization of ZnO-NPs. Decrease in oxidative stress was found with the dose-dependent culture of HEK-293 cells with these functionalized ZnO-NPs. Cell viability and morphology, as observed using AFM and inverted microscope, was retained with the prescribed dosages of the functionalized nanoparticles while at higher dosages they caused cytotoxicity and death. Diethylamine (DEA) modified ZnO-NPs and their functionalization with GSH and curcumin were found more effective in managing oxidative stress in cells. Present study could help in designing economical and bio-compatible functionalized non-toxic nanoparticles designed for managing oxidative stress leading to possible therapeutical and medicinal uses.

Extensive efforts are being made in enhancing the photoconversion efficiency of TiO2 based dye sensi- tized solar cells (DSSC) using different approaches. In this work, the Sn-doped TiO2 nanopowder was sensitized with flower extracts of Dahlia Violet (DV), Rabbit flower (RF) and their mixed extract separately other than the com- mercial N719 dye and DSSC characteristics were studied. Hydrothermal method was used to synthesize Sn-doped TiO2 for 48 h at 150 C. X-ray diffraction, UV-Vis, FTIR and Raman scattering were used to characterize the syn- thesized powder. DSSCs of the synthesized powder was fabricated using conventional sandwich type technique sealed with Surlyn polymer film. The photocurrent-volt- age characteristics were measured under solar simulated light using source-meter. It is interesting to note that the flower extract resulted in comparable photoconversion ef- ficiency as that of N719 dye. When the powder was sen- sitized with N719, 1.66 % efficiency was achieved while mixed extract resulted in 1.28 %, DV in 0.99 % and RF in 0.52 % efficiency. The results of various analysis tech- niques and cell characteristics are correlated.

Extensive efforts are being made in enhancing the photoconversion efficiency of TiO2 based dye sensitized solar cells (DSSC) using different approaches. In this work, the TiO2 nanopowder was sensitized with rare earth metal and DSSC characteristics were studied. Commercial powder (P25) was calcined at 450 °C and sensitized with Nd. X-ray diffraction, UV–Vis, FTIR and Raman scattering were used to characterize nanopowder and found that Nd-sensitization resulted in formation of additional absorption/vibrational bands. The photocurrent–voltage characteristics were measured under simulated light using source-meter. It is interesting to note that the photoconversion efficiency has doubled when commercial powder was just calcined. When the powder was sensitized with Nd, efficiency has tremendously increased to 4.51 % for commercial powder and 9.10 % for calcined powder indicating the effect of Nd-sensitization. The results of various analysis techniques and cell characteristics are correlated.

With an increasing focus on applied research, series of single/composite materials are being investigated for device development to detect several hazardous, dangerous, and toxic molecules. Here, we report a preliminary attempt of an electrochemical sensor fabricated using pristine Ni and Cr–doped nano tin oxide material (SnO2) as a tool to detect agro-hazardous material, i.e. Organophosphate (OP, chlorpyrifos). The nanomaterial was synthesized using the solution method. Nickel and chromium were used as dopant during synthesis. The synthesized material was calcined at 1000 °C and characterized for morphological, structural, and elemental analysis that showed the formation of agglomerated nanosized particles of crystalline nature. Screen-printed films of powder obtained were used as a matrix for working electrodes in a cyclic voltammogram (CV) at various concentrations of organophosphates (0.01 to 100 ppm). The CV curves were obtained before and after the immobilization of acetylcholinesterase (AChE) on the nanomaterial matrix. An interference study was also conducted with hydroquinone to ascertain the selectivity. The preliminary study indicated that such material can be used as suitable matrix for a device that can easily detect OP to a level of 10 ppb and thus contributes to progress in terms of desired device technology for the food and agricultural-industries.

Extensive research studies are being carried out to significantly improve the sensing characteristics of pesticide sensors (chloropyrifos, organophosphates (OP)) especially at ultra low concentrations using advance fabrication and characterization techniques. We report feasibility study of pesticide sensing, using nanostructured zinc oxide (ZnO) and acetylcholinesterase (AChE) immobilized ZnO films, at ultra low concentrations (10 to 1000 ppb). ZnO nanoparticles (NPs) were synthesized by non-aqueous sol–gel method. Reduced glutathione (GSH) was coated on as-synthesized ZnO NPs by physical mixing. FESEM observation revealed spherical particles of about 10–20 nm in diameter having fairly uniform shape distribution. Thick films of these powders were printed on pre-printed electrodes using conventional screen printing technique. AChE was immobilized on the films by physical adsorption method. It is found that bare ZnO NPs are insensitive to pesticides while GSH coated ZnO NPs exhibit monotonous increase of sensitivity as a function of OP concentration over the wide range (10 ppb to 1000 ppb) with sensitivity of 2.1 A/ppm/cm2, detection limit of 3 ppb and regression coefficient of 0.92. Electrochemical measurement indicated that sensors can be used for few times due to the known inhibitory nature of OP and AChE reaction.

Here we report an easy method to improve the optoelectronic properties of commercially available TiO2 nanopowder using extracts of various flowers viz. Calendula Orange (CO), Calendula Yellow (CY), Dahlia Violet (DV), Dahlia Yellow (DY), Rabbit flower (RF), Sweet Poppy (SP), Sweet Williams (SW) and their Mixed Extracts (ME). Various analysis techniques such as UV-Vis, FTIR, FESEM, XRD, and Raman spectroscopy were used to characterize for elemental, structural and morphological properties of the unmixed/mixed TiO2 nanopowder. TiO2 nanopowder was also calcined at 550 degrees C. Thick films of the these unmixed/mixed powder were printed, using conventional screen printing method, on fluorine doped tin oxide (FTO) substrate with organic binders and dried at 45 degrees C. The photoconducting properties are investigated as a function of wavelength from ultra-violet (UV) to infra-red (IR) region at a constant illumination intensity. Photocurrent gradually decreases when irradiated from UV to IR region. In case of unmixed and uncalcined TiO2, conductance decreased continuously whereas when extracts are added, a flat region of conductance is observed. The overall effect of extracts (colour pigments) is seen as an increase in the photoconductance. Highest photoconductance is observed in case of DY flower extract. Anthocyanins, present in flowers are known to have antioxidative properties and hence can contribute in photoconduction by reducing the surface adsorbed oxygen. This investigation indicates the potential use of flower extracts for dye sensitized solar cell (DSSC).

Nanosized niobium oxide powders were synthesized with a yield of approximately 87% using a simple and facile soft-chemical process. Niobium pentachloride (Nb2Cl5) was used as the precursor which was first converted into niobium ethoxide and then hydrolysed with water to synthesize niobia nanopowder. The synthesized powder was calcined at 500 degrees C for phase conversion to end-centered monoclinic as confirmed by diffraction studies and elemental analysis with a chemical composition in the ratio of Nb:O as 1:2.5. The molecular framework of Nb-O-Nb stretching and asymmetric frequency was confirmed by FT-IR, UV-visible and Raman spectroscopic studies. The size, shape and surface morphology of the powders were observed by SEM and TEM which indicated particle sizes of approximately 20 nm. The surface area of 20 m2/g, pore volume of 0.0538 cm2/g and the average pore size of 6.5 nm2 for the calcined sample were obtained with the help of nitrogen adsorption/desorption method using the Barrett-Joyner-Halenda (BJH) method which indicates that the synthesized powder can be used for catalysis and other surface sensitive applications.

This work presents glucose sensing characteristics of palladium doped tin oxide (SnO 2 ) thin films deposited by modified plasma enhanced chemical vapor deposition (CVD) technique as a function of deposition temperature (400–600 °C) and at fixed radio frequency (RF) plasma power of 150 W. Stannic chloride (SnCl 4 ) and palladium hexafluroacetyleacetonate (Pd(C 5 HF 6 O 2 ) 2 ) were used as precursors for tin and palladium respectively whereas oxygen (O 2 , 100 sccm) was used as reactant gas. Granular morphology is observed with tetragonal rutile structure. Diffraction peaks related to SnO 2 and Pd 2 Sn are observed at all the deposition temperatures. Photoelectron peaks related to Sn (3 d , 3 p , 4 d ), Pd 3 d , O 1 s , C 1 s and N 1 s were detected with varying intensities as a function of deposition temperature. Glucose oxidase (GO x ) was immobilized by physical adsorption (by soaking films in 1000 units of GO x solution for three hours). The sensitivity to glucose increases with slight non-linearity from 5 mg/dl to 360 mg/dl and found decreasing with increasing deposition temperature. Electrochemical studies indicated rapid electron transfer kinetics and hence reversible electron transfer reactions.

The photoconducting properties of a unit microflower of zinc oxide are investigated as a function of wavelength from UV to IR region at constant illumination intensity. Synthesized flowers were trapped in 2 microm gap, between pre-prepared gold microelectrodes, using AC dielectrophoresis. Photocurrent drastically increases upon illumination in the UV region, whereas it gradually reduces when irradiated in visible and IR region. Higher photoconductivity in UV region is correlated to band to band transition upon illumination. In visible region, deep level transitions are expected which intern exhibits comparatively low photocurrent. Photoconduction in IR region is only due to the adsorbed surface oxygen species. This investigation suggests the potential application of ZnO nanostructures for various optoelectronic device applications.

Nanomaterial-based photoluminescence (PL) diagnostic devices offer fast and highly sensitive detection of pesticides, DNA and toxic agents. Here we report a label-free PL genosensor for sensitive detection of Vibrio cholerae that is based on a DNA hybridization strategy utilizing nanostructured magnesium oxide (nMgO; size >30 nm) particles. The morphology and size of the synthesized nMgO were determined by transmission electron microscopic (TEM) studies. The probe DNA (pDNA) was conjugated with nMgO and characterized by X-ray photoelectron and Fourier transform infrared spectroscopic techniques. The target complementary genomic DNA (cDNA) isolated from clinical samples of V. cholerae was subjected to DNA hybridization studies using the pDNA-nMgO complex and detection of the cDNA was accomplished by measuring changes in PL intensity. The PL peak intensity measured at 700 nm (red emission) increases with the increase in cDNA concentration. A linear range of response in the developed PL genosensor was observed from 100 to 500 ng/μL with a sensitivity of 1.306 emi/ng, detection limit of 3.133 ng/μL and a regression coefficient (R2) of 0.987. These results show that this ultrasensitive PL genosensor has the potential for applications in the clinical diagnosis of cholera.