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A novel resistive chemical-mechanical sensor for hydrogen gas detection was designed and manufactured by using MEMS processing technology. The sensor combines a composite piezoresistor of silver nanowires-polyimide and a palladium sputtered microcantilever, and the optimized structure of which has been obtained through theoretical and simulation analysis. With a series of experimental testing, the fabricated sensor achieved the ultra-high sensitivity of 2825, 8071, 28250 and 47083 for hydrogen detection at the concentration of 0.4%, 0.8%, 1.2%, 1.6% and 2.0%, respectively. The ultra-high sensitive detection for hydrogen was enabled from the synergistic function of both the surface resistance effect between the palladium coated cantilever and silver nanowires-polyimide piezoresistor, and the bulk resistance effect of the silver nanowires-polyimide piezoresistor. In addition, the sensor also demonstrates excellent stability, which has high potential for practical hydrogen gas detection.

SU-8 photoresist has been more and more widely used as a structural material in micro electromechanical system (MEMS) because of its low cost and excellent biocompatibility. However, the inferior mechanical and thermal performances immensely impinge the reliability of the MEMS device based SU-8 and accordingly restrict its application. Here we report the mechanical and thermal performance of SU-8 reinforced by the multilayer glass fabric with the MEMS technology. The finite element simulation and specific experiment are conducted, which confirm that the reinforced SU-8 composites have a 281% increase in Young's modulus and a 64% decrease in coefficient of thermal expansion (CTE) compared with pure SU-8. Additionally, the improved mechanism has also been analyzed, including the excellent interface bonding between the SU-8 and glass fabric, and the high-bond energy of Si–O-Si chain structures in glass fabric. Furthermore, the glass fabric reinforced SU-8 could still possess a high light transmittance to maintain the ability of lithography patterning. Therefore, it is believed that the strategy proposed here may satisfy higher requirements of MEMS devices, which guarantees its practical applications in the functional microstructures.

Acid-alkaline balance plays a crucial role in all biological processes. Accordingly, monitoring pH changes will help us to understand the functional status of these physiological and pathological processes. Though fluorescent probes may be a useful tool for detecting pH changes, and there are many limitations to currently available probes, such as background interference, potential cytotoxicity, and poor cell permeability, which call for a solution urgently. In this work, a rhodamine-derived colorimetric and ratiometric sensor (Rh–HN) was fabricated for monitoring pH change via the mechanism of fluorescence resonance energy transfer (FRET). Rh–HN has been shown to possess several advantages over other probes, such as high sensitivity, outstanding permeability, and low toxicity. Besides, the fluorescence intensity ratio (F526/F592) of Rh–HN displays a pH-sensitive response from 2.0 to 7.5 (pKa = 5.05) and linear response from pH 3.8 to 6.4, which was desirable for mapping pH change in the biological systems. Besides, the results indicated that Rh–HN generated a pH-dependent response regulated by switchable forms between closed and opened spirolactam ring. Overall, Rh–HN has accomplished sensing and mapping of pH in living cells, bacteria, and zebrafish. Those results demonstrated that the great potential of Rh–HN in sensing and visualizing pH in the living biosystem.

Molybdenum nitride (δ–MoN) is an important functional material due to its impressive catalytic, energy storage, and superconducting properties. However, the synthesis of δ–MoN usually requires extremely harsh conditions; thus, the insight into δ−MoN is far behind that of oxides and sulfides of molybdenum. Herein, we report that ultrathin δ−MoN nanosheets are prepared at 270 °C and 12 atm. WN, VN, and TiN nanosheets are also synthesized by this method. The δ−MoN nanosheets show strong surface plasmon resonance, high conductivity, excellent thermal and chemical stability as well as a high photothermal conversion efficiency of 61.1%. As a promising surface enhanced Raman scattering substrate, the δ−MoN nanosheets exhibit a 8.16 × 106 enhanced factor and a 10−10 level detection limit for polychlorophenol., Molybdenum nitride is promising for catalysis, energy storage and Raman scattering, but it is synthesized under harsh conditions. Here the authors synthesize highly crystalline molybdenum nitride nanosheets using a relatively mild, non-aqueous solvothermal approach that can be extended to other nitrides.

The development of Ti3C2Tx-based high performance electrode materials has been proposed to meet the practical requirements of supercapacitors. In this study, transition metal complexes decorated MXene Ti3C2Tx hybrid electrode nanocomposites are fabricated by a facile polyvinylpyrrolidone (PVP)-assisted liquid impregnation strategy (abbreviated as PVP-M/akTi3C2Tx (M = Mn or Ni)). The intercalated Ti3C2Tx is observed to possess a distinct layered structure wrapped by cloud-like Mn/Ni complexes, which form a heterojunction to help the charge transfer of PVP-M/akTi3C2Tx in aqueous electrolytes such as KOH, LiOH, Li2SO4 and Na2SO4. The electrochemical performance of pristine and modified MXene in the above electrolytes changes greatly, mainly due to the difference of electrolytes’ ionic radius and conductivity. Typically, the PVP-Mn/akTi3C2Tx and PVP-Ni/akTi3C2Tx nanocomposites exhibit superior specific capacitances of 154.6 F g−1 and 167.65 F g−1 at 0.3 A g−1 current density in 1 M KOH electrolyte, respectively. Moreover, due to the complete progressive activation process of the electrode materials, the specific capacitance further increased by 25% and 56% after thousands of cycles, and finally kept at 95.70% and 96.21% of the maximum value respectively, indicating the superstability of these electrode materials. This study provides a new perspective to tailor the microstructures of Ti3C2Tx electrode materials for energy applications.

Designing a new adsorbent with recyclability, high efficiency and biodegradability is important for treating heavy metals contamination but remains a severe challenge. In this work, a novel type of hydrogel biosorbents based on pullulan and polydopamine were designed for heavy metal ions removal from aqueous solution. The physicochemical properties of the prepared pullulan/polydopamine (Pu/PDA) hydrogels were fully characterized by thermal gravimetric analysis, Fourier transform infrared spectroscopy, rheology, scanning electron microscopy, swelling and compression tests. We observed that their mechanical strength, pore size, water absorption and retention properties could be nicely controlled by adjusting the PDA concentration in the pre-gel solution. Subsequently, the adsorption ability of designed Pu/PDA hydrogels to Cu2+, Co2+ and Ni2+ was investigated in detail. These hydrogels presented excellent adsorption capability for heavy metal ions and matched well with the pseudo-second-order kinetic model and Freundlich isotherm model. Overall, having tunable physicochemical properties coupled with the high absorption ability for heavy metal ions, these Pu/PDA hydrogels may be a promising strategy for removal of pollutants from aqueous solution.

Summary Compared with the noble-metal surface-enhanced Raman scattering (SERS) substrates activated by the surface plasmon resonance (SPR)-induced electromagnetic mechanism (EM), the relative low sensitivity and stability of the chemical mechanism (CM)-based substrates are the biggest obstacles to their applications. Herein, we report that quasi-metallic VO2 nanosheet arrays can be used as a sensitive and stable SERS substrate. The lowest detectable limit of analyte adsorbed on the VO2 nanosheets achieves 10−10 M and the maximum Raman enhancement factor (EF) reaches 6.7 × 107, which is comparable with that of the noble metals. The experimental and theoretical results demonstrate that the SERS performance of the VO2 nanosheets comes from the strong interfacial interactions based on charge transfer and the vigorous SPR effects. Our research results demonstrate that quasi-metals are very promising SERS detection platforms and reveal that CM, like EM, contributes significantly to the SERS activity of quasi-metals., Graphical Abstract, Highlights • Surface-enhanced Raman scattering (SERS) on quasi-metallic VO2 • High SERS enhancement factor and low limit of detection have been achieved • Synergistic effect of electromagnetic enhancement and chemical enhancement, Physical Chemistry; Electromagnetics; Materials Property; Nanomaterials

Multifunctional core-shell nanocarriers based on zinc oxide (ZnO)-gated magnetic mesoporous silica nanoparticles (MMSN) were prepared for cancer treatment through magnetic targeting and pH-triggered controlled drug release. Under an external magnetic field, the MMSN could actively deliver chemotherapeutic agent, daunomycin (DNM), to the targeted sites. At neutral aqueous, the functionalized MMSN could stably accommodate the DNM molecules since the mesopores were capped by the ZnO gatekeepers. In contrast, at the acid intercellular environment, the gatekeepers would be removed to control the release of drugs due to the dissolution of ZnO. Meanwhile, ZnO quantum dots not only rapidly dissolve in an acidic condition of cancer cells but also enhance the anti-cancer effect of Zn2+. An in vitro controlled release proliferation indicated that the acid sensitive ZnO gatekeepers showed well response by the ‘on-off’ switch of the pores. Cellular experiments against cervical cancer cell (HeLa cells) further showed that functionalized MMSN significantly suppressed cancer cells growth through synergistic effects between the chemotherapy and Zn2+ ions with monitoring the treatment process. These results suggested that the ZnO-gated MMSN platform is a promising approach to serve as a pH-sensitive system for chemotherapies delivery and Zn2+ controlled release for further application in the treatment of various cancers by synergistic effects.

Inspired by the ring-opening reaction of rhodamine probe induced by metal ions, we proposed a positive charge regulating strategy and designed an “always-on” and “water-soluble” fluorescent probe (o-RPM) based on rhodamine amide bearing o-pyridinium. To our knowledge, o-RPM was the first always-on opening form of spirolactam which can endure broad pH range (pH 3.5–13.0) and aprotic environment. IR and NMR spectrum were used to assess the distribution of conjugation system induced by positive charge in pyridinium moiety. The geometries of o-RPM were calculated using Gaussian software at DFT/B3LYP/6-31 G(d) level. The always-on opening form of o-RPM should be attributed to inductive and conjugation effects resulting from proximal positive charge. Meanwhile, positive charge contributed to the dissolution of o-RPM in aprotic and/or protic solvents. In addition, always-on and water-soluble o-RPM exhibited excellent membrane penetration, and was successfully used as a specific tracker to map the mitochondrial distributions in living MCF-7 cells, due to the nature characteristic of positive charge. It is anticipated that the strategy of ring-opening form of rhodamine spirolactam induced by positive charge might be hopeful to regulate the “on-off-on” state of spirolactams in the biomedical and biological fields.

This article presents a flexible implantable device fabricated on a polyimide (PI) catheter for targeted treatment of cardiovascular diseases. The copper (Cu) microcoil was fabricated on a PI catheter surface using the rotated UV lithography system and surrounding electroplating technology. The simulation on the magnetic fields generated from the Cu microcoil with 0.2 A current and the driving force analysis on magnetic nanoparticles (MNPs) were conducted. The results demonstrated the precise control of MNPs motions within the magnetic fields generated from the Cu microcoil fabricated on the PI surface. The maximum temperature that increased from the magnetized Cu microcoil was 2 °C at room temperature, suggesting no induced hyperthermia. Moreover, the electrical performance of Cu microcoil was excellently stable in a variety of environments, such as wet, dry, and mechanical fatigue conditions. In vivo tests displayed great biocompatibility of the fabricated device within the carotid artery of a rat model. The directional assembly of MNPs can be achieved by a Cu microcoil fabricated on the surface of a PI catheter. The fabricated device shows notable advantages in promoting the targeted therapeutic strategy of cardiovascular diseases.

Herein, spindle-shaped block copolymer (BCP) nanoparticles are used in seeded polymerization of methyl methacrylate as a novel approach to generating cylindrical nanostructures. The chain-extension of BCP seeds by an amorphous coil-type polymer within the seed core composed of semifluorinated liquid-crystalline blocks triggers the deforming, stretching, and directional growth of the seeds along the long axis, eventually leads to nanorods.

Intensity- and amplitude-weighted average lifetimes, denoted as τI and τA hereafter, are useful indicators for revealing Förster resonance energy transfer (FRET) or fluorescence quenching behaviors. In this work, we discussed the differences between τI and τA and presented several model-free lifetime determination algorithms (LDA), including the center-of-mass, phasor, and integral equation methods for fast τI and τA estimations. For model-based LDAs, we discussed the model-mismatch problems, and the results suggest that a bi-exponential model can well approximate a signal following a multi-exponential model. Depending on the application requirements, suggestions about the LDAs to be used are given. The instrument responses of the imaging systems were included in the analysis. We explained why only using the τI model for FRET analysis can be misleading; both τI and τA models should be considered. We also proposed using τA/τI as a new indicator on two-photon fluorescence lifetime images, and the results show that τA/τI is an intuitive tool for visualizing multi-exponential decays.

Perovskite structures of organic and inorganic halides are peculiar structures with many interesting properties. Using their photoelectric effect, the structures have been used in photocells, photoelectric sensors, and light-emitting diodes. In conventional perovskite film crystallization, which is a one-step method, the MAPbI3 crystals form disordered needlelike crystals at room temperature. Such needlelike crystal films have rough surfaces and low coverage to the substrate, resulting in insignificant photoelectric effects. With the assistance of an electric field and three-dimensional (3D) printing, the direction of the perovskite needlelike crystal can be arranged to make it orderly. In this way, the photoelectric sensor of the ordered MAPbI3 perovskite needlelike crystal film can be prepared. This sensor has high sensitivity, high stability, and high response speed. Moreover, it has anisotropy and higher photoelectric sensitivity in the direction perpendicular to the needle crystal. Most interestingly, the sensors respond differently to polarized light in different directions, and this effect can be used to detect the direction and degree of polarization of polarized light.

Two polar molybdenum(VI) iodates(V), NH4[MoO3(IO3)] (1) and KRb[(MoO3)2(IO3)2] (2), have been prepared by a hydrothermal method. They crystallize in noncentrosymmetric (NCS) space groups Pna21 and ...

High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone (NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH3NH3PbI3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.

Lithium metal is among the most promising anode materials for high-energy batteries due to its high theoretical capacity and lowest electrochemical potential. However, uncontrolled lithium decomposition and dendrite formation have hindered its practical applications. Here, we propose a facile and effective strategy using thionyl chloride (SOCl2) as electrolyte additive to in-situ build a stable interfacial protective layer on lithium anode to prevent Li dendrite growth. Furthermore, the decomposition of SOCl2 could produce active sulfur to offer extra capacity for cathode in full battery. As a result, the as-assembled lithium-sulfur battery delivered an ultra-high discharge capacity (2202.3 mA h g−1 at 400 mA g−1) and excellent rate performance (1348.6 mA h g−1 at 3000 mA g−1), as well as remarkable cycling performance. This study reveals an effective avenue to suppress the Li-dendrites growth and provide a significant step towards safe and high-energy Li-S batteries.

Recently, perovskite solar cells have attracted great attention because of their outstanding photovoltaic performance and ease of fabrication. High-quality perovskite films hold a key in getting highly efficient perovskite solar cells. Solution-processed fabrication technique is the most widely adopted for preparing perovskite films because of its low cost. In the solution-proceed perovskite films, solvents not only play the role of dissolving the solute but also participate in the crystallization of perovskite. In the one-step method, solvents play key roles in controlling morphology, widening process window, and achieving room-temperature crystallization of perovskite films. In addition, the solvents play important roles in controlling the nuclei/growth, suppressing volume expansion during the two-step method. Especially, the solvent can induce grain coarsening during the annealing process. A deep understanding of the multiplicity of roles during the formation of perovskite films will help understand the formation mechanism of perovskite films. Here, a systematic review on the progress in fabrication of high-quality perovskite films by making use of solvent to control the crystallization is presented. Meanwhile, we elucidate the key roles of solvent in the fabrication of high-quality perovskite films.

This paper proposed to tailor the layer microstructures of two-dimensional Ti3C2Txvia a facile Li+ pre-pillaring and successive pillaring strategy by various cations. By ion exchange with pre-intercalated Li+, as well as "coulombic attraction" to electronegative Ti3C2Tx, various inexpensive and column-like K+, Ca2+, Mg2+, Al3+ and NH4+ cations were migrated into the Ti3C2Tx interlayers. By expanding the interlayer about 17.02%, as well as enhancing the electron density of Ti atoms and C atoms, the Al3+ intercalated MXene Ti3C2Tx sheets delivered the highest specific capacity of 175 F g-1 at 0.3 A g-1. Coupling the Ti3C2Tx-Al3+ working electrode with a platinum counter electrode and a Hg/HgO reference electrode, the single electrode (calculated from a three-electrode system) exhibited a high energy density of 87.5 W h kg-1 and a high power density (2100 W kg-1) with an ultra-long and stable cycling performance. The binding energies of the intercalated ions with hydroxyl groups, the Bader charge distribution and degree of electron localization were evaluated by density functional theory calculations to further validate the ultra-high energy storage capacity of Al3+ pillared-Ti3C2Tx in the present study.

Facultative intracellular pathogens are able to live inside and outside host cells. It is highly desirable to differentiate their cellular locations for the purposes of fundamental research and clinical applications. In this work, we developed a novel analysis platform that allows users to choose two analysis models: amplitude weighted lifetime (τ A) and intensity weighted lifetime (τ I) for fluorescence lifetime imaging microscopy (FLIM). We applied these two models to analyse FLIM images of mouse Raw macrophage cells that were infected with bacteria Shigella Sonnei, adherent and invasive E. coli (AIEC) and Lactobacillus. The results show that the fluorescence lifetimes of bacteria depend on their cellular locations. The τ A model is superior in visually differentiating bacteria that are in extra- and intra-cellular and membrane-bounded locations, whereas the τ I model show excellent precision. Both models show speedy performances that analysis can be performed within 0.3 s. We also compared the proposed models with a widely used commercial software tool (τ C, SPC Image, Becker & Hickl GmbH), showing similar τ I and τ C results. The platform also allows users to perform phasor analysis with great flexibility to pinpoint the regions of interest from lifetime images as well as phasor plots. This platform holds the disruptive potential of replacing z-stack imaging for identifying intracellular bacteria.

High-quality perovskite films with large grains and long carrier lifetime are crucial for efficient solar cells. It is a simple and effective way to increase the perovskite grain size by adding some additives in the precursor solution. Here, we use a low-toxicity and low-volatility organic compound of 1-ethyl-2-pyrrolidone (NEP) as an additive in the PbI2(PbBr2)/dimethylformamide precursor solution to form a Lewis adduct of PbI2·NEP, which facilitate forming perovskite intermediate embedded with NEP molecules. The residual NEP molecules are kept in the narrow space between the intermediate film and substrate during annealing by using a closed-steam annealing method, which prolong the dissolution-recrystallization process. With assistance of the residual NEP, high-quality perovskite films with smooth surface, PbI2 free, high crystallinity, large columnar grains, and long carrier lifetime are fabricated. Correspondingly, the power conversion efficiency of the best perovskite solar cells is enhanced signific...

Perovskite films are usually fabricated by a solution-processed method due to its low cost and ease of fabrication. The organic solvent plays multiple roles in the growth of perovskites. Here, we i...

Lightweight, ultrathin, and flexible electromagnetic interference (EMI) shielding materials with high electromagnetic shielding effectiveness (SE) and excellent mechanical robustness are greatly desired for miniaturized and highly integrated electronics. Herein, for the first time, a freestanding, ultrathin, and flexible Ti3C2Tx/poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS) composite film with a “brick-and-mortar” structure is biomimetically designed and fabricated via a vacuum-assisted filtration process. The ultrathin polymeric composite film with a weight ratio 7:1 of Ti3C2Tx to PEDOT:PSS is only 11.1 μm in thickness but exhibits a high EMI SE value of 42.10 dB. Meanwhile, the tensile strength increases considerably from 5.62 to 13.71 MPa and the corresponding ruptured strain increases from 0.18 to 0.29% compared with pure Ti3C2Tx MXene film, respectively. Moreover, the hybrid film displays a superior conductivity of 340.5 S/cm and an outstanding specific EMI shielding efficiency ...

Superhydrophobic surface has attracted enormous interests due to its attractive potential applications. Here, we prepare all carbon nanotube hybrid films simply by depositing multi-walled carbon nanotubes on strong single-walled carbon nanotube films through vacuum filtration. The hybrid films behave some exciting superhydrophobic properties of a large water contact angle of 152° and an ultra-low sliding angle of only 2°. The rebounding height of a water droplet dipping from 5 cm above the hybrid film reaches 9.4 mm, which is 3 times that of on the natural lotus leaf. The superhydrophobic hybrid film also have high specific loading capacity of 627 g/g, more than 12 times that of the natural lotus leaf. The hybrid films can mimic lotus leaf in water repelling, self-cleaning, and carrying heavy things quite well.

Thermal annealing plays multiple roles in fabricating high quality perovskite films. Generally, it might result in large perovskite grains by elevating annealing temperature, but might also lead to decomposition of perovskite. Here, we study the effects of annealing temperature on the coarsening of perovskite grains in a temperature range from 100 to 250 °C, and find that the coarsening rate of the perovskite grain increase significantly with the annealing temperature. Compared with the perovskite films annealed at 100 °C, high quality perovskite films with large columnar grains are obtained by annealing perovskite precursor films at 250 °C for only 10 s. As a result, the power conversion efficiency of best solar cell increased from 12.35% to 16.35% due to its low recombination rate and high efficient charge transportation in solar cells.

CeO2 nanoparticles were dispersed on hexagonal boron nitride (hBN) supports by a rotary chemical vapor deposition method using Ce(DPM)4 as a precursor at 600°C, and extra oxygen was introduced to assist the decomposition and oxidation of the precursor. A significant composition and structure dependent nature was observed on the oxidation supply rate by eliminating the organic molecules and fragments and assisting the decomposition of the Ce(DPM)4 precursor. The CeO2 nanoparticles were 10-15 nm in diameter, with the measured spacings of the lattice fringes as 0.31 and 0.27 nm, corresponding to (111) and (200) plane, respectively, which are in agreement with the standard data (JCPDS: 34-0394). In addition, with the oxidative decomposition of precursor Ce(DPM)4, CeO2 nanoparticles were produced and then coated on the ceramic surface through the CVD method, presenting the preferred orientation. The deposition mechanism was also discussed.

Compositional engineering of mixed halides is an effective approach to fabricate highly efficient perovskite solar cell. The mixed halide perovskite of MAPbI3-xClx attracts a great of attentions due to its excellent optoelectronic properties. However, the role of chlorine in MAPbI3-xClx is still under discussion by now. Here we introduce PbCl2 as additives into PbI2/DMF solution to study its effects on the formation of MAPbI3-xClx film, which is fabricated from Lewis acid-base adducts through a modified two step method. We demonstrate that the chloride ions have positive roles in fabrication of high quality perovskite MAPbI3-xClx films, characterized by high crystallization, strong grain orientation, large grain size and lower trap densities. Compared to perovskite solar cells without chloride incorporation, the performance of solar cells based on MAPbI3-xClx improves significantly due to its high carrier mobility, efficient carrier transportation and low recombination in device.

Copper nanowires (Cu NWs) encapsulated with polypyrrole (PPy) (Cu@PPy) have been fabricated by a facile liquid-phase reduction with copper (II) chloride as precursor. The as-synthesized Cu NWs grow along the crystal orientation of (1 1 0) and the encapsulated polypyrrole layer is also observed on the surface of Cu NWs. The Cu@PPy nanostructure is investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). And the experimental results show that the synthesized Cu@PPy are uniform and cross each other with the average width of 160 nm. Additionally, the results of XRD and XPS indicate the Cu@PPy nanostructure has excellent oxidation resistance and temporal stability.

The properties of organic–inorganic hybrid perovskites greatly depend on their compositions. Here, we investigate the crystallization of methylammonium lead mixed halide (MAPbI3–xBrx) from microdroplets by adjusting the molar ratio of iodine to bromine in precursor solution, which helps to control the morphology, crystallinity, and physical properties of the perovskite materials. The composition of the precursor solutions has profound effects on the crystallization and perovskite morphology. It tends to form needle intermediate crystals of MAPbI3−xBrx·DMF from the precursor solution at low bromine concentration, while it tends to form flake or cubic perovskite of MAPbI3−xBrx at high bromine concentration. There is evident composition segregation of bromine when the perovskite and its intermediate grow freely from the solution at low temperature. At a high growing temperature of 100 °C, continuous perovskite films consisting of large crystal domains with sizes up to 100 μm are fabricated from the precursor...

Generally, residual solvent is embedded in perovskite precursor films fabricated from the Lewis adduct method. Most of the research focus on the ligand function of the solvent in forming a solvate complex for fabricating high quality perovskite films. However, little attention has been paid to the latent function of the solvent in the perovskite precursor films during the annealing process due to its fast extravasation at high temperature. Here, we develop a sandwich configuration of substrate/perovskite precursor films/PC61BM to retard the extravasation of solvent during annealing. We find that the restrained solvent induces an obvious solvent-mediated dissolution–recrystallization process, leading to high quality perovskite films with large columnar grains. There is mass transportation from small grains to large grains in the dissolution–recrystallization process, which follows the Ostwald ripening model. Inverted planar solar cells are fabricated on the basis of this annealing method. The photovoltaic ...

The physical properties of organic–inorganic hybrid perovskite materials are greatly influenced by their composition, crystallinity, and morphology. Here, we investigate the growth of CH3NH3PbI3−xBrx perovskite from micro-droplets of a methylammonium iodide/lead acetate/dimethylformamide precursor solution added with different concentrations of PbBr2, which helps to control the morphology and crystallinity of the perovskite film. We find that both perovskite and its intermediate containing an acetate group growing from the micro-droplets. By adding some PbBr2, there is a tendency to form cubic perovskite crystals due to partial substitution of iodine with bromide. There is composition segregation when the crystals grow freely from the droplets. Smooth and uniform CH3NH3PbI3−xBrx perovskite films with a tunable band gap are thus fabricated from the precursor solution added with PbBr2.

The aqueous zinc-ion hybrid supercapacitor (ZIHC) has become an emerging energy storage device due to its safety and low cost. Herein, a new pizza-like heterostructure of Ti3C2Tx intercalated by N-doped-carbon-wrapped Bi2S3 is fabricated by in-situ growth. The specific capacitance of Ti3C2Tx/Bi2S3@N-C electrode is as high as 653 F g−1 at 1 A g−1, which is significantly higher than other binary composites or similar MXene-based materials in literature. The ZIHC are assembled with Ti3C2Tx/Bi2S3@N-C and Zn foil as electrodes, possessing high specific capacitance of 150.33 F g−1 at 1 A g−1, and a maximum energy density of 46.98 W h kg−1 at a power density of 750 W kg−1. The excellent performance of Ti3C2Tx/Bi2S3@N-C is mainly attributed to the synergistic effect of the three components: (a) highly conductive Ti3C2Tx as the substrate shortens the electron transport path; (b) the in-situ growth of Bi2S3 on Ti3C2Tx layers makes full use of Bi2S3 active sites; (c) the innovative introduction of dopamine can not only make Bi(NO)3 evenly dispersed, but also form the “cross-bridge” N-C film, which further improves the binding between Ti3C2Tx substrate and Bi2S3 and reduces the internal resistance greatly. This study proposes a new in-situ growth strategy for a ternary heterostructure, which may offer a new avenue for the development of high-performance electrode materials.

China's toilet modernization has enabled thousands of villages to separate their feces and urines from the greywater or washing wastewater. Human feces and urine are usually used as raw materials for fertilizers, but the lack of understanding of discharge characteristics of washing wastewater in China rural areas affects the development of treatment technology and the reuse of treated water. In this study, a village in the lower reaches of the Yangtze River was selected to investigate the discharge characteristics of washing wastewater, and four kinds of subsurface constructed wetlands were used for treatment and reuse. The results showed that the production of washing wastewater in rural aeras was 59–232 L/(cap .d), with an average of 121 L/(cap .d). The bathing wastewater contributed the highest proportion of 46.19%. COD was identified as the key pollutants with average concentration of 337 mg/L. Compared with domestic wastewater, the concentrations of TN and TP were much lower with the average of 11.1 mg/L and 0.6 mg/L respectively. After treated by the constructed wetland with ceramsite, volcanic rock and anthracite as composite substrate, the effluent water met the requirements of paddy field crop irrigation, and the removal rates of COD, TN and TP achieved 61.5%, 68.8% and 70.5% respectively. Wetland plants and modular design had significant positive effects on the removal of nitrogen and phosphorous, but little effect on COD removal. The fecal coliforms in the effluent were all lower than 4.0 lg (MPN/L) in the four constructed wetlands, indicating they were not the limiting factors for irrigation reuse.

Perovskite solar cells (PSCs) have great potentials in photovoltaics due to their high power conversion efficiency and low processing cost. PSCs are usually fabricated from PbI2/dimethylformamide solution with some toxic additives, such as N-methyl pyrrolidone and hexamethylphosphoramide. Here, we use an environmental friendly aprotic polar solvent, 1,3-dimethyl-2-imidazolidinone (DMI), to fabricate perovskite films. By adding 10 vol% DMI in the precursor solution, high-quality perovskite films with smooth surface are obtained. By increasing annealing temperature from 100 to 130 °C, the average grain size of the perovskite increases from ~ 216 to 375 nm. As a result, the efficiency of the PSCs increases from 10.72 to 14.54%. Electronic supplementary material The online version of this article (10.1186/s11671-017-2391-3) contains supplementary material, which is available to authorized users.

A kind of coating nanostructure, Ag nanoparticles coated with multilayered reduced graphene oxide (RGO), is fabricated by employing a three-step reduction method in an orderly manner, which is significantly different from the conventional structures that are simply depositing or doping with Ag nanoparticles on RGO via chemical reduction. The as-prepared nanostructure is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electronic diffraction (SEAD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results show that the obtained Ag/RGO nanostructure is observed to be a perfect coating structure with well dispersed Ag particles, which is responsible for the remarkable oxidation resistance. The results of XPS spectra indicate the content of metallic Ag is far greater than that of Ag oxides despite of prolonged exposure to the air, which fully demonstrate the excellent stability of thus coating nanostructure.

Bisphenol A (BPA) is an effective endocrine-disrupting compound (EDC) that causes adverse effects on human health and environment. Therefore, it is indispensable to construct efficacious methods for evaluating the level of BPA to enhance the quality of life. In this study, a facile electrochemical sensor based on reduced graphene oxide-silver/poly- l -lysine nanocomposites (RGO-Ag/PLL) modified glassy carbon electrode (GCE) is proposed for the detection of BPA. The synthesized RGO-Ag/PLL nanocomposites displays high electrocatalytic activity towards the electrochemical oxidation of BPA. Differential pulse voltammetry (DPV) is used as an analytical method for the quantitative determination of BPA, and the fabricated electrochemical sensor exhibits a linear response to BPA in the range of 1–80 μM with the limit of detection (LOD) of 0.54 μM at a signal-to-noise ratio of 3. Additionally, the developed RGO-Ag/PLL/GCE sensor is applied to detect the BPA in drinking water, and obtains satisfactory results.

Random-oriented 0.5LaFeO3-Bi4Ti3O12 thin films were prepared via a sol–gel method on (111)Pt/Ti/SiO2/Si(100) substrates. According to X-ray diffraction analysis, the films have a single-phase Aurivillius perovskite structure with a space group Fmm2. As expected, the coexistence of ferroelectric and ferromagnetic properties was detected at room temperature. The remanent polarization (2Pr) and the saturated magnetization (Ms) are 61.94 μC/cm2 and ∼0.90 emu/cm3, respectively. Furthermore, a magneto-dielectric effect was demonstrated at room temperature with a magneto-dielectric coefficient of 0.67% under a low magnetic field of 0.25 T, probably resulting from the charge ordering of Fe2+ and Fe3+. Finally, a dielectric relaxation behavior was observed around 130 K, which is also related to the coexistence of Fe2+ and Fe3+.

Over the past decades, gallium (Ga) compounds have gained importance in the field of cancer treatment. Gallium acts as an iron mimic and disturbs iron-dependent propagation and other processes in tumor cells. However, the toxicity of gallium was also well documented in vitro and in vivo in animals. Though the oral administration of gallium in humans is less toxic, it has also been shown that a long period of administration could induce tumor fibrosis. Chromium (Cr), a naturally occurring heavy metal, is commonly used in industrial processes and can cause severe health problems in humans. It has been found to be closely involved in the metabolism of nucleic acids, proteins and fats in humans. Cr(III) salts can be used as micronutrients and dietary supplements. However, similar to gallium (Ga3+), chromium (Cr3+) can build up to an excessive degree that is harmful to the human body. Therefore, it would be of great interest to develop chemosensing for the selective and sensitive detection of gallium and chromium ions in vitro and in vivo. Herein, we reported that an NBD-based (4-chloro-7-nitrobenzo-2-oxa-1,3-diazole) fluorescent probe (NBDT) was fabricated with demonstrated extraordinary specificity and sensitivity. A swift response toward Ga3+ and Cr3+ ions was discovered using fluorescence enhancement over a wide pH range and with cycle stability. Furthermore, lighted up by Ga3+ and Cr3+ ions in vitro, this NBDT sensor was successfully applied to detect exogenous Ga3+ and Cr3+ ions in MDA-MB-231 and HepG2 cells. Additionally, using zebrafish as the in vivo model, we demonstrated the capability of this NBDT for detecting and imaging Ga3+ and Cr3+ ions in zebrafish. Taken together, this NBDT has indicated great potential for detecting and monitoring Ga3+ and Cr3+ ions in vitro and in vivo.

Chemosensing is one of the widest and powerful techniques for response to anions and cations in living systems serving as bio-probes. Meanwhile, copper(II) (Cu(II)) widely exists in the environment and the human body as a common trace element, which plays an necessary role in most physiological processes. Thus, it is extremely urgent to explore means for effective, rapid and convenient detection of Cu(II) in living cells. Herein, we introduce a novel strategy for designing triphenylamine (TS) and coumarin-based (CS) functional sensors for Cu(II) detection with fluorescence “OFF” switching mechanism by blocking intramolecular charge transfer (ICT). Based on this design strategy, we have demonstrated two kinds of fluorophores sensors with aunique new fluorescent dye and excellent photophysical properties, which have shown rapid recognition of Cu(II) via a stoichiometric ratio of 2:1 and the proposed binding mode was confirmed by the single-crystal structure of CS-Cu(II) complex. In addition, we have carried out density functional theory (DFT) calculation with the B3LYP exchange functional employing RB3LYP/6-31G basis sets to get insight into the mechanism of Cu(II)-sensors alongside their optical properties. Furthermore, the sensors were capable of bio-imaging Cu(II) in living cancer cells (HepG2, A549 and Hela) with low cytotoxicity and good biocompatibility shown. Taken together, We expect that this novel strategy would provide new insight into the development of Cu(II) detection techniques and could be used more for biomedical applications.

A novel six-membered rhodamine-based fluorescent probe (6G-ClO) was developed from 2-formyl rhodamine (6G-CHO) and used for hypochlorite detection in water and HUVEC cells. Different from planar penta cycle of rhodamine spirolactam, there was a twist six-membered spirocyclic hydrazone in 6G-ClO optimized by Gaussian software at DFT/B3LYP/6-31G(d) level. The high selectivity, high sensitivity and fast response of 6G-ClO towards ClO− would be attributed to the twist six-membered spirocycle. Test-strip prepared with 6G-ClO was successfully used to semi-quantitatively indicate the concentration of ClO− in water. 6G-ClO can also quantitatively detect the concentration of ClO− in tap water and swimming pool water. The detection limit of 6G-ClO was as low as 12 nM. The co-localization staining of HUVEC cells further verified that 6G-ClO could specifically accumulate in lysosomes and capture exogenous/endogenous ClO− in living lysosomes. 6G-ClO would be a practical probe for real-time monitoring of ClO− in the biological and real water samples.

In this paper, a brand-new amorphous Ti3C2Tx/BiCuS2.5 electrode material was first invented by a facile in-situ deposition strategy, whose workable voltage window was enlarged up to 2.0 V (−1.4 V~0.6 V) with an improved capacity to 840 C g−1 at 1 A g−1 due to a “baton relay” mechanism. When the Ti3C2Tx/BiCuS2.5 electrode material was assembled for an aqueous symmetrical supercapacitor, the device exhibited a maximum energy density of 56.1 Wh kg−1 at a power density of 15.3 kW kg−1. After 10,000 cycles, the energy density was even elevated to 63.325 Wh kg−1. When the Ti3C2Tx/BiCuS2.5 material was used for a zinc-ion capacitor cathode, the device exhibited an energy density of 298.4 Wh kg−1 at a power density of 7200 W kg−1. The energy density retention of 95% after 7000 cycles and 82% after 10000 cycles clearly proved the good recyclability of Ti3C2Tx/BiCuS2.5 electrode. Based on the attentive DFT simulation and XPS analysis, the energy storage mechanism was ascribed to the co-existence of intercalation and redox battery-type capacity. This work opens a new direction with new electrode materials workable at a high voltage range for the construction of high specific energy supercapacitors.

Lithium-sulfur (Li-S) batteries have been regarded as one of the most promising candidates for next-generation energy storage devices owing to their low cost and high energy density. However, the shuttle effect and sluggish conversion of lithium polysulfides (LiPSs) are still thorny issues for its practical application. Here, an efficient three-dimensional conductive CoS2/rGO aerogel is constructed and used as a trapping-catalyst sulfur host to improve the overall performance of Li-S batteries. CoS2 nanoparticles, uniformly in-situ anchored on rGO sheets, provide strong trapping ability to LiPSs and then catalyze its conversion, thus inhibiting the shuttle effect and accelerating the reaction kinetics. Highly conductive porous rGO aerogel ensures fast ion and electron transfer for electrochemical reaction and electrocatalysis process. As a result, the electrode exhibits a high initial capacity of 1457 mAh g−1 at 0.2 C, superior high-rate capability of 1156 mAh g−1 at 2 C, ultra-low capacity decay rate per cycle of 0.04% at 1 C for 400 cycles, and a high areal capacity of 5.7 mA h cm−2 (high sulfur loading of 6.37 mg cm−2).

The optical properties of silicon-on-insulator (SOI) samples, modified in Si thin film by multiple-time Si+ self-ion-implantation followed by annealing, have been well investigated. The SOI materials implanted by single energy can obtain many kinds of luminous centers, while the larger density appears in the samples implanted by multiple energy. After annealing at 700 °C, the sample implanted three times forms a luminescence peak with high luminescence intensity and narrow peak width near 0.8 eV. It is speculated that this peak is D1 peak and multiple implantation combined with high temperature annealing can promote the formation of D1 line luminous center in SOI.

Feasibility of the multi-effect distillation (MED) process was investigated experimentally and theoretically in present work to deal with the high-salinity organic reverse osmosis concentrates (ROCs) generated by the double membrane process for the treatment of wastewater from the refining and chemical enterprises. Two key problems involving the behaviors of organic and inorganic impurities in the ROCs during evaporation and process optimization of MED thermally and economically were highlighted. The experimental results indicated that about 6% and 8% of organic impurities volatilized during evaporation and entered into the produced water and the tail gas, respectively. The produced water and the tail gas which met the related China National standards could be reused or vented directly without further treatment. However, scaling of calcium sulfate was drastically occurred in the evaporator when about 30% water was recovered, indicating the necessity of removal of the hardness in ROCs before evaporation. A forward flow MED model established on Aspen Plus platform was employed to perform the thermal and economic analysis for the ROCs treatment. Performance analysis including the Gained Output Ratio (GOR), fresh steam flow and specific heat transfer area as functions of the effect number and the heating steam temperature were conducted. The results showed that the performance of the MED system was significantly influenced by effect number over the heating steam temperature. An increase in the effect number would improve the thermodynamic performance of MED system but increased the capital costs. The model established in this work could provide a theoretical guidance for the development of MED process dealing with ROCs.

The solvent embedded in the intermediate phase is widely observed in the fabrication of perovskite films. The perovskite precursor films obtained from Lewis adducts through molecular exchange contain some residue solvent. It has an intrinsic solvent annealing effect during the annealing process. Here, we pre-deposit a protective layer on the perovskite precursor films to retard the escape of solvent during the annealing process. The restricted solvent strengthens the solvent annealing effect during the formation of perovskite films. As a result, the perovskite quality, including grain size and crystallization, is improved significantly, which leads to efficient charge transportation, low recombination rate, and enhancement of the photovoltaic performance of the corresponding perovskite solar cells.

The search for photocatalytic materials that can harvest a wide spectrum of solar light, from ultraviolet (UV) to near infrared (NIR) regions remains one of the most challenging missions. Here, by in situ growing plasmonic W18O49 nanocrystals on TiO2 nanosheets with exposed {001} facets, a hybrid photocatalyst with broad spectrum photocatalytic properties has been fabricated, which can harvest UV, visible, and NIR light to decompose organic contaminants. The results present a new concept that plasmonic transition-metal oxides with a high concentration of oxygen vacancies can be used as non-noble metal photosensitizers to design efficient photocatalysts with high activity.

A two-step method is widely used to fabricate highly efficient perovskite solar cells. In a typical two-step method, CH3NH3PbI3 perovskites are fabricated from PbI2 films through an intercalation reaction between PbI2 and CH3NH3I, which usually have a rough surface and residual PbI2 due to a compact PbI2 structure. Here, we introduce some strong Lewis bases into PbI2/DMF solutions in the first step, which is helpful in controlling the morphology of PbI2 films with a mesoporous structure. The mesopores in the PbI2 films provide not only space for accommodating the volume expansion during the reaction between PbI2 and CH3NH3I, but also channels for CH3NH3I solution to diffuse into the PbI2 films, which helps eliminate the residual PbI2 and the dissolution and recrystallization process. As a result, smooth perovskite films without residual PbI2 are easily obtained. The power conversion efficiency, stability and reproducibility of the perovskite solar cells fabricated from the optimized mesoporous PbI2 films improved simultaneously due to the improvement in perovskite films. This work reveals the key roles of solvents (boiling point, Lewis basicity) in controlling the microstructure of the PbI2 films.

Uniform Au–WO3 porous hollow spheres have been synthesized on a large-scale by a general in situ reaction between weakly reductive carbonaceous microspheres and oxidative noble-metal precursors without foreign reducing agents and stabilizing agents. The hybrid materials exhibit excellent activity for visible-light photocatalytic degradation of organic pollutants.

Polycrystalline Bi 4 YFeTi 3 O 15 thin films were prepared on (111)Pt/Ti/SiO 2 /Si through a sol-gel process. X-ray diffraction analysis shows the films have a single-phase four-layered Aurivillius structure with the space group of Fmm 2. As expected, the Bi 4 YFeTi 3 O 15 films exhibit the coexistence of ferroelectric and weak ferromagnetic properties with the remanent polarization (2 P r ) ∼ 53.62 μC/cm 2 and the saturated magnetization ( M s ) ∼ 0.50 emu/cm 3 at room temperature. More interestingly, both dielectric relaxation behavior and room-temperature magneto-dielectric effect were observed in the Bi 4 YFeTi 3 O 15 films, probably resulting from the coexistence of Fe 2+ and Fe 3+ . The conduction mechanism of the films from 10 to 300 kV/cm is dominated by Ohmic mechanism, space-charge-limited current (SCLC), and trap-filled-limit (TFL) current, respectively. The leakage current density remains lower than 1.03 × 10 −5 A/cm 2 under the poling field below 300 kV/cm at 300 K.

Perovskite solar cells have a puzzling phenomenon of current hysteresis. Here, we modulate the hysteresis by applying a poling voltage. Charge accumulations are detected in the perovskite solar cells. Two interacting capacitors are identified through dynamic voltage measurement. We elucidate that the current hysteresis originates mainly from the polarization and depolarization of electric dipoles of CH3NH3+ under an external electric field due to the intrinsic ferroelectric properties of perovskite. The polarization leads to charge accumulation at the surface of perovskite, which establishes a polarization-induced electric field. The polarization-induced electric field affects the charge transport inside the solar cells, resulting in the current hysteresis. The polarization of electric dipoles can be modified by the poling and sweeping voltage, which makes the hysteresis exhibit a history-dependent effect.

Yolk–shell architectures have attracted extensive attention owing to their unique structure and infusive applications. MoS2 is regarded as one of the most promising catalytic materials for hydrogen evolution by the splitting of water. In this work, a simple self-template solvothermal approach is developed for the synthesis of novel MoS2 yolk–shell microspheres with a hierarchical porous structure by reacting MoO2 microspheres with L-cysteine. A dissolutionrecrystallization formation mechanism is proposed for the MoS2 yolk–shell microspheres. Owing to structural superiority, the new material architecture exhibits improved photoelectrochemical properties, including efficient hydrogen evolution reaction catalytic activities, a high photocurrent density, a small overpotential, and a low charge-transfer resistance.