Ultraviolet color image sensor based on CsPbBr3 inorganic perovskite nanocrystal film.

Ultraviolet and color imaging require different image sensors and optical channels, which results in large size, complex structure, and high cost of imaging systems. Here, we report a novel, to the best of our knowledge, image sensor that combines ultraviolet and color imaging functions. The fabrication of this image sensor is achieved by coating high-transparency CsPbBr3 perovskite nanocrystals in a polymer film on the color filter layer of a silicon-based detector. The film, serving as an ultraviolet photoluminescent layer, exhibits high transparency, exceeding 91.5% at wavelengths beyond the photoluminescence peak of 513 nm. During ultraviolet imaging, the film converts ultraviolet light into visible light, which passes through the green filter layer to reach the detector for imaging. During visible light imaging, red light, green light, and most of the blue light pass through the CsPbBr3 perovskite nanocrystal film and color filter layer to reach the detector for imaging. As a result, the image sensor can capture both 257 nm solar-blind ultraviolet images and color photos in the visible light.

Phot2-regulated relocation of NPH3 mediates phototropic response to high-intensity blue light in Arabidopsis thaliana.

Two redundant blue-light receptors, known as phototropins (phot1 and phot2), influence a variety of physiological responses, including phototropism, chloroplast positioning, and stomatal opening in Arabidopsis thaliana. Whereas phot1 functions in both low- and high-intensity blue light (HBL), phot2 functions primarily in HBL. Here, we aimed to elucidate phot2-specific functions by screening for HBL-insensitive mutants among mutagenized Arabidopsis phot1 mutants. One of the resulting phot2 signaling associated (p2sa) double mutants, phot1 p2sa2, exhibited phototropic defects that could be restored by constitutively expressing NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3), indicating that P2SA2 was allelic to NPH3. It was observed that NPH3-GFP signal mainly localized to and clustered on the plasma membrane in darkness. This NPH3 clustering on the plasma membrane was not affected by mutations in genes encoding proteins that interact with NPH3, including PHOT1, PHOT2 and ROOT PHOTOTROPISM 2 (RPT2). However, the HBL irradiation-mediated release of NPH3 proteins into the cytoplasm was inhibited in phot1 mutants and enhanced in phot2 and rpt2-2 mutants. Furthermore, HBL-induced hypocotyl phototropism was enhanced in phot1 mutants and inhibited in the phot2 and rpt2-2 mutants. Our findings indicate that phot1 regulates the dissociation of NPH3 from the plasma membrane, whereas phot2 mediates the stabilization and relocation of NPH3 to the plasma membrane to acclimate to HBL.

Sensitivity of pressure sensors enhanced by doping silver nanowires.

We have developed a highly sensitive flexible pressure sensor based on a piezopolymer and silver nanowires (AgNWs) composite. The composite nanofiber webs are made by electrospinning mixed solutions of poly(inylidene fluoride) (PVDF) and Ag NWs in a cosolvent mixture of dimethyl formamide and acetone. The diameter of the fibers ranges from 200 nm to 500 nm, as demonstrated by SEM images. FTIR and XRD results reveal that doping Ag NWs into PVDF greatly enhances the content of ß phase in PVDF. This ß phase increase can be attributed to interactions between the Ag NWs and the PVDF matrix, which forces the polymer chains to be embedded into the ß phase crystalline. The sensitivity of the pressure sensors agrees well with the FTIR and XRD characteristics. In our experiments, the measured sensitivity reached up to 30 pC/N for the nanofiber webs containing 1.5 wt% Ag NWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE), (77/23)]. This study may provide a new method of fabricating high performance flexible sensors at relatively low cost compared with sensors based on [P(VDF-TrFE), (77/23)].

Long-Term Stable Complementary Electrochromic Device Based on WO3 Working Electrode and NiO-Pt Counter Electrode.

Complementary electrochromic devices (ECDs) composed of WO3 and NiO electrodes have wide applications in smart windows. However, they have poor cycling stability due to ion-trapping and charge mismatch between electrodes, which limits their practical application. In this work, we introduce a partially covered counter electrode (CE) composed of NiO and Pt to achieve good stability and overcome the charge mismatch based on our structure of electrochromic electrode/Redox/catalytic counter electrode (ECM/Redox/CCE). The device is assembled using a NiO-Pt counter electrode with WO3 as the working electrode, and PC/LiClO4 containing a tetramethylthiourea/tetramethylformaminium disulfide (TMTU/TMFDS2+) redox couple as the electrolyte. The partially covered NiO-Pt CE-based ECD exhibits excellent EC performance, including a large optical modulation of 68.2% at 603 nm, rapid switching times of 5.3 s (coloring) and 12.8 s (bleaching), and a high coloration efficiency of 89.6 cm2·C-1. In addition, the ECD achieves a good stability of 10,000 cycles, which is promising for practical application. These findings suggest that the structure of ECC/Redox/CCE could overcome the charge mismatch problem. Moreover, Pt could enhance the Redox couple's electrochemical activity for achieving high stability. This research provides a promising approach for the design of long-term stable complementary electrochromic devices.

Proton and Redox Couple Synergized Strategy for Aqueous Low Voltage-Driven WO3 Electrochromic Devices.

Aqueous electrolytes possess non-combustible and eco-friendly features compared to organic electrolytes, leading them to be more suitable for application in smart windows for daily use. However, limited by the narrow electrochemical window of water (1.23 V), its use in conventional electrochromic devices (ECDs) would result in irreversible performance loss, which arises from decomposition caused by high voltage. Here, we propose a synergistic scheme combining a redox couple-catalytic counter electrode (RC-CCE) strategy with protons as guest ions. With the help of the intelligent matching of the reaction potentials of the RC and amorphous WO3 electrochromic electrodes and the highly active and fast kinetic features of protons, it successfully reduces the working voltage range of the device to 1.1 V. The assembled HClO4-ECD can possess an overall modulation rate (350-1200 nm) of 0.43 and 0.94 at -0.1 and -0.7 V, respectively, and a modulation of 66.8% at 600 nm at -0.7 V. Moreover, compared with other guest ions, the proton-based ECD exhibits higher coloration efficiency, a broader color modulation capability, and better stability. In addition, the house model equipped with the proton-based ECD effectively blocks solar radiation, which provides a potential solution for the design of aqueous smart windows.

Dielectric studies on the heterogeneity and interfacial property of composites made of polyacene quinone radical polymers and sulfonated polyurethanes.

Sulfonated polyurethane (PUI, matrix) is synthesized and composited with polyacene quinone radical polymers (PAQRs, filler). The polarization mechanism of these polymers and composites were investigated in terms of their frequency, temperature, and filler-concentration-dependent dielectric properties. We found that PUI/PAQR composites have a high permittivity, which is attributed to the filler-matrix interfacial polarization and the contact effect. The PAQR-concentration-dependent permittivity of different PUI/PAQR composites reveals a percolation threshold at 20-30 wt % with scaling exponents that indicate the intercluster polarization. The frequency dependence of dielectric response is well-fitted by using the Debye and Cole-Cole functions on the basis of the structural diagrams and equivalent circuit, leading to a detailed evaluation on heterogeneous structures of different PUI/PAQR composites.

Flexible Piezoresistive Pressure Sensor Based on Electrospun Rough Polyurethane Nanofibers Film for Human Motion Monitoring.

Flexible piezoresistive pressure sensors have been attracted a lot of attention due to their simple mechanism, easy fabrication, and convenient signal acquisition and analysis. Herein, a new flexible piezoresistive sensor based on microstructured electrospun rough polyurethane (PU) nanofibers film is assembled. The microstructured PU film with tiny bumps is prepared in one step via electrospinning technology, which imparts a microstructured rough upper surface and a smooth lower surface. With this unique microstructure, we have made it possible for PU/Ag films to serve as sensing layers for piezoresistive sensors by introducing a silver conductive layer on the surface of electrospun PU film. The fabricated piezoresistive pressure sensor delivers high sensitivity (10.53 kPa-1 in the range of 0-5 kPa and 0.97 kPa-1 in the range of 6-15 kPa), fast response time (60 ms), fast recovery time (30 ms), and long-time stability (over 10,000 cycles). This study presents a fabrication strategy to prepare the microstructured PU nanofiber film using electrospinning technology directly, and the as-developed sensor shows promise in applications such as wrist pulse measurement, finger movement monitoring, etc., proving its great potential for monitoring human activities.

Versatile Photo/Electricity Responsive Properties of a Coordination Polymer Based on Extended Viologen Ligands.

Responsive chromogenic materials have attracted increasing interest among researchers; however, up until now, few materials have exhibited multifunctional chromogenic properties. The coordination polymers (CPs) provide intriguing platforms to design and construct multifunctional materials. Here, a multifunctional photo/electricity responsive CP named Zn-Oxv, which is based on the "extended viologen" (ExV) ligand, was synthesized. The Zn-Oxv exhibited reversible photochromism, photomodulated fluorescence, electrochromism and electrofluorochromism. Furthermore, we prepared Zn-Oxv thin films and investigated electrochromic (EC) properties of viologen-based CPs for the first time. Zn-Oxv thin films showed excellent EC performance with a rapid switching speed (both coloring and bleaching time within 1 s), high coloration efficiency (102.9 cm2/C) and transmittance change (exceeding 40%). Notably, the Zn-Oxv is by far the fastest CP EC material based on redox-active ligands ever reported, indicating that the viologen-based CPs could open up a new field of materials for EC applications. Therefore, viologen-based CPs are attractive candidates for the design of novel multi-responsive chromogenic materials and EC materials that could promise creative applications in intelligent technology, dynamic displays and smart sensors.

Heteroatom-Doped Nickel Oxide Hybrids Derived from Metal-Organic Frameworks Based on Novel Schiff Base Ligands toward High-Performance Electrochromism.

The tenets of coordination chemistry enable researchers to design and develop nanostructured materials based on metal-organic frameworks (MOFs). Herein, for the first time, we applied the Schiff base system to MOF derivatives as a strategy for the heteroatom introduction into carbon-based metal oxides toward electrochromic applications. The presented Ni-MOF thin films based on Schiff base ligands were prepared by a facile and economical reductive electrosynthesis approach, facilitating the scalable fabrication of large-size electrochromic films derived from MOFs. After the pyrolysis, the desired N-doped NiO@C (N-C@NiO) films can achieve a high cycling stability (500 cycles with 7% contrast attenuation) and coloration efficiency (80.18 cm2/C) via different pyrolysis procedures. In addition, the one-step fabricated N-C@NiO shows an excellent ability of contrast modulation (68%@580 nm) with merely 3.6% transmittance at the colored state. These improvements in electrochromic properties are attributed to hierarchical porous heterostructures and influenced by the N/C ratio and C-N bonding configuration, indicating that N-C@NiO systems derived from Schiff base MOFs are promising for low-transmittance displays.

Dynamically Cross-Linked Hydrogel Electrolyte with Remarkable Stretchability and Self-Healing Capability for Flexible Electrochromic Devices.

It is desired to develop self-healing gel electrolytes for flexible electrochromic devices (ECDs) due to the demand of healing damages caused during operations. We here report a hydrogel electrolyte with remarkable self-healing capability, excellent stretchability, and ionic conductivity. The hydrogel electrolyte was synthesized via one-step copolymerization of glycerol monomethacrylate (GMA) and acrylamide (AAm) in the presence of borate. Within the hydrogel electrolyte, dynamic cross-linking is expected to be formed due to the borate-didiol complexation and hydrogen-bonding interactions. As a result, the hydrogel electrolyte demonstrates an excellent self-healing efficiency of up to 97%, a fracture strain of 1155%, a fracture toughness of 136.6 kJ m-3, and a fracture stress of 13.0 kPa. Additionally, a flexible ECD based on the hydrogel electrolyte and an electrochromic layer of poly(3,4-(2,2-dimethyl-propylenedioxy)thiophene) (PProDOT-Me2) was assembled and evaluated. The device is found to be stable in both mechanical and optical properties over 1000 operation cycles. This study may provide a promising way for self-healing electrolyte gels to be utilized in a variety of flexible electrochemical devices, including ECDs, supercapacitors, and batteries.

Boosting light harvesting and charge separation of WO3 via coupling with Cu2O/CuO towards highly efficient tandem photoanodes.

Photoanodes based on semiconductor WO3 have been attractive due to its good electron mobility, long hole-diffusion length, and suitable valence band potential for water oxidation. However, the semiconductor displays disadvantages including a relatively wide bandgap, poor charge separation and transfer, and quick electron-hole recombination at the interface with the electrolyte. Here we present a significantly improved photoanode with a tandem structure of ITO/WO3/Cu2O/CuO, which is prepared first by hydrothermally growing a layer of WO3 on the ITO surface, then by electrodepositing an additional layer of Cu2O, and finally by heat-treating in the air to form an exterior layer of CuO. Photocurrent measurements reveal that the prepared photoanode produces a maximum current density of 4.7 mA cm-2, which is, in comparison, about 1.4 and 5.5 times the measured values for ITO/WO3/Cu2O and ITO/WO3 ones, respectively. These enhancements are attributed to (1) harvested UV, visible, and NIR light of the solar spectrum, (2) accelerated charge separation at the heterojunction between WO3 and Cu2O/CuO, (3) better electrocatalytic activity of formed Cu x O than pure Cu2O, (4) formation of a protective layer of CuO. This study thus may lead to a promising way to make high-performance and low-cost photoanodes for solar energy harvesting.

Enhanced electrochromic switches and tunable green fluorescence based on terbium ion doped WO3 films.

Multifunctional WO3-based materials have been increasingly attracting attention due to their unique physical and electrochemical nature. In this work, the luminescent species, terbium (Tb) ions, were first successfully doped into WO3 films by a hydrothermal method to incorporate their electrochromic and photoluminescent functions. The amorphous state and porous net structure are introduced, which can be attributed to the inhibited orientation growth caused by the occupation of Tb ions in the WO3 lattice. Here, the optimal 13% Tb-WO3 film exhibits enhanced electrochromic properties: a high transmittance modulation of 66.71%; a fast response speed of less than 10 s; an improved CE value of 48.33 cm2 C-1 at 680 nm; and cycling stability over 600 cycles without obvious degradation, arising from its larger active surface area. Meanwhile, its green-colored emission could be realized under 260 nm UV light and is electro-switchable upon applying voltage.

Detection of Carcinoembryonic Antigens Using a Surface Plasmon Resonance Biosensor.

Carcinoembryonic antigen (CEA) is an oncofoetal cell-surface glycoprotein that serves as an important tumor marker for colorectal and some other carcinomas. In this work, a CEA immunoassay using a surface plasmon resonance (SPR) biosensor has been developed. SPR could provide label-free, real-time detection with high sensitivity, though its ability to detect CEA in human serum was highly dependent on the analytical conditions employed. We investigated the influences of various analytical conditions including immobilization methods for anti-CEA antibody and composition of sensor surface on the selective and sensitive detection of CEA. The results show that anti-CEA antibody immobilized via Protein A or Protein G caused a large increase in the resonance signal upon injection of human serum due to the interactions with IgGs in serum, while direct covalent immobilization of anti-CEA antibody could substantially reduce it. An optimized protocol based on further kinetic analysis and the use of 2nd and 3rd antibodies for the sandwich assay allowed detecting spiked CEA in human serum as low as 25 ng/mL. Furthermore, a self-assembled monolayer of mixed ethylene-glycol terminated alkanethiols on gold was found to have a comparable ability in detecting CEA as CM5 with thick dextran matrix and C1 with short flat layer on gold.

Note: Microelectrode-shielding tip for scanning probe electron energy spectroscopy.

We report a novel microelectrode-shielding tip (ME tip) for scanning probe electron energy spectroscopy (SPEES). The shielding effect of this tip is studied through comparing the detection efficiency with the normal tip by both experiment and simulation. The results show that the backscattering count rate detected by the SPEES instrument using the normal tip begins to decrease as the tip approaches to the sample surface within 21 µm, while that using the ME tip only starts to drop off within 1 µm. This indicates that the electron energy spectra can be measured with the ME tip at a much closer tip-sample distance. Furthermore, it is also demonstrated that the ME tip can be used to obtain topography of the sample surface in situ simultaneously.

Facile Fabrication of Micro-Nano Structured Triboelectric Nanogenerator with High Electric Output.

In this article, a new method is used to fabricate a high-performance triboelectric nanogenerator (TENG), which is convenient and cost-effective. A polyformaldehyde (POM) film with novel structures is prepared through electrospinning and is combined with a polytetrafluoroethylene (PTFE) film to assemble micro-nano structured TENG. The short-circuit current (I s) and open-circuit voltage (V o) of the TENG are up to 0.4343 mA and 236.8 V, respectively, and no significant change is observed by applying different frequencies of external impact forces from 1 to 10 Hz. Finally, we successfully drive an electrochromic device (ECD) directly using TENG within just 2 min for the first time.

Highly Regiosymmetric Homopolymer Based on Dioxythiophene for Realizing Water-Processable Blue-to-Transmissive Electrochrome.

A highly regiosymmetric homopolymer based on a diethyl malonate derivatized 3,4-propylenedioxythiophene (ProDOT) monomer was synthesized through FeCl3 oxidative polymerization and postpolymerization functionalization to realize a water-processable blue-to-transmissive switching electrochromic polymer (WPECP-blue). As an electrochromic material, the polymer has a high electrochromic contrast ΔTmax=56% at 580 nm and a relatively fast switching speed t95=1.8 s, and shows only contrast loss of 11% (from 56% to 45%) at square wave potential step of 5 s over 11,000 switching cycles, making it a desirable candidate for electrochromic applications such as windows and displays.

AIEE-Active and Electrochromic Bifunctional Polymer and a Device Composed thereof Synchronously Achieve Electrochemical Fluorescence Switching and Electrochromic Switching.

A novel alternating polymer, ProDOT-TPE, with aggregation-enhanced fluorescent emission and electrochromic properties based on thiophene and tetraphenylethene derivatives was designed, synthesized, and characterized. The polymer displays weak photoluminescence in tetrahydrofuran, but its corresponding film prepared by spray-coating exhibits yellow-green fluorescent light at 540 nm. The color of the polymer film could be switched from bright yellow to navy blue by applying a relatively low voltage. An electrochromic device (ECD) of the polymer was fabricated that differs from common ECDs because both its color and fluorescent state could be synchronously switched by an applied voltage, making the polymer a unique candidate for electrochemical fluorescence and electrochromic applications.

Distinct Properties of Nanofibrous Amorphous Ice.

We make glassy water in the form of nanofibers by electrospraying liquid water into a hyperquenching chamber. It is measured with means of differential scanning calorimetry, wide angle X-ray diffraction and Raman spectroscopy. It is found that two apparent glass transitions at Tg1 = 136 K and Tg2 = 228 K are detected and non-crystallized water is observed at temperatures up to 228 K. This finding may expand the research objects for liquid water at low temperatures.