Search

A "signal-off" photoelectrochemical (PEC) sensing platform has been designed for the ultrasensitive detection of DNA methylation levels and multiple methylated sites. The platform employs tungsten trioxide and TpPa-1-COF loaded by gold nanoparticle (AuNPs@WO3@TpPa-1-COF) composite material as the photoactive component and p-type reduced graphene (rGO) as an efficient quencher. The PEC signal of AuNPs@WO3@TpPa-1-COF composite is effectively quenched in the presence of p-type rGO, because p-type rGO can compete with AuNPs@WO3@TpPa-1-COF to deplete light energy and electron donors. In addition, a hybrid strand reaction (HCR) amplification strategy fixes more target DNA and then combines with rGO-modified anti-5-methylcytosine antibody to facilitate ultrasensitive DNA methylation detection. Under optimal conditions, DNA methylation can be measured within a linear concentration range of 10–14 to 10–8 M, with an exceptionally low detection limit of 0.19 fM (S/N = 3). At the same time, the platform can conduct quantitative determination of multi-site methylation, with the linear equation △I = 44.19LogA + 61.43, and the maximum number of methylation sites is 5. The sensor demonstrates high sensitivity, excellent selectivity, and satisfactory stability. Furthermore, the proposed signal-off PEC strategy was successfully employed to detect DNA methylation in spiked human serum samples, with recoveries ranging from 93.17 to 107.28% and relative standard deviation (RSD) ranging from 1.15 to 5.49%. [ABSTRACT FROM AUTHOR]

Highly photoactive 3D nanoflower-like FeIn2S4/CdS heterostructures were synthesized by hydrothermal treatment and low-temperature cation exchange. The FeIn2S4/CdS displayed 14.5 times signal amplification in contrast to FeIn2S4 alone. It was applied as a photoactive substrate to construct a label-free photoelectrochemical (PEC) aptasensor for ultrasensitive determination of kanamycin (KAN). Under the optimal conditions, the constructed PEC aptasensor displayed a wide linear range (5.0 × 10−4 ~ 5.0 × 101 ng mL−1) and a low detection limit (S/N = 3) of 40.01 fg mL−1. This study provides some constructive insights for preparation of advanced photoactive materials and exhibits great potential for quantitative determination of antibiotics in foods and environmental samples. [ABSTRACT FROM AUTHOR]

• The waste Bitter apple (BA) peel has been carbonized to synthesize photoactive Carbon Dots (CD). • It efficiently photo-degrades the Crystal Violet (CV) dye under the presence of sunlight. • The insight of degradation mechanism was explained by trap experiment, using different scavengers. A simple and sustainable approach is described for the synthesis of photoactive carbon dots (CD) as an efficient photo-catalytic material. The photoactive-CD has been fabricated by simply charring the peels of Bitter Apple (BA). It is somewhat similar to the biochar synthesis. The photoactivity of BA peel derived photoactive-CD was tested under the illumination of sunlight for photodegradation of a pollutant organic dye, crystal violet (CV). A possible mechanism has been proposed for photodegradation of dye based on the trap experiment, where electron and holes were majorly responsible. BA peel derived photoactive-CD showed remarkable results concerning the photodegradation of CV (20 ppm in ~ 90 min) under sunlight illumination as compared to the dark conditions. [ABSTRACT FROM AUTHOR]

Herein, novel photoactive materials, MOF-derived porous hollow carbon nanobubbles@ZnCdS multi-shelled dodecahedral cages (C@ZnCdS MSDCs)， were synthesized via continuous chemical etching, sulfurization, cation-exchange and calcination strategies. Due to the synergistic effect between the porous shells and the carbon-layer coating， C@ZnCdS MSDCs displayed superior photoelectrochemical (PEC) performance. The synthesized C@ZnCdS MSDCs were assembled onto TiO 2 modified ITO electrodes to form a type-II heterostructures. Then, Au nanoparticles (NPs) were deposited on the surface of ITO/TiO 2 /C@ZnCdS MSDCs. Benefiting from the unique structure and performance merits of photoactive materials, a label-free PEC sensing platform based on ITO/TiO 2 /C@ZnCdS MSDCs/Au was successfully constructed for CEA detection. Under optimal conditions, the PEC biosensor exhibited a wide linear range (0.00005–500 ng mL−1) and low detection limit (2.28 fg mL−1). The proposed PEC biosensor also showed good stability, specificity, reproducibility and acceptability in human serum. The prepared C@ZnCdS MSDCs would be a promising photoactive material for PEC biosensors. Most importantly, this work opens up new horizons for the application of MOFs-derived hollow carbon materials in sensing. • MOFs-derived C@ZnCdS MSDCs with superior PEC performance were synthesized for the first time. • This work opens up a promising approach for synthesis of multi-shell hollow carbon materials. • The PEC biosensor mechanism of TiO 2 /C@ZnCdS MSDCs/Au for CEA was studied. • TiO 2 /C@ZnCdS MSDCs/Au-based biosensor exhibited superior sensing performances. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sective photo dissociative C C bond of highly photoactive bis-2-benzylidenemalononitrile (BBM) is observed under UV irradiation. • The C C bond is more polarizable, highly active and susceptible for photodissociation. • Product A (2-(4-formylbenzylidene)malononitrile), formed by the selective C C bond photodissociation and has been isolated. • The pseudo 1st order kinetics and dipolar mechanism. Abstract Photophysical study of highly photoactive bis-2-benzylidenemalononitrile (BBM) has been investigated in solution using UV–vis, fluorescence and NMR spectroscopic techniques. The seletive photodissociation can be attributed to the presence of highly polarized C C bond, attached to dicyno groups (CN). Nevertheless, the observed photodissociation of BBM is highly solvent specific and temperature sensitive. The product A (2-(4-formylbenzylidene)malononitrile), formed by the selective photodissociation of BBM under UV irradiation has been isolated and identified by NMR studies. The photodissociation followed the pseudo 1st order kinetics with a rate constant (k) 10−3-10-4.s-1. Moreover the mechanistic study of selective photodissociation of bis-2-benzylidenemalononitrile (BBM) has been investigated and found to follow the dipolar mechanism path during photochemical reaction. [ABSTRACT FROM AUTHOR]

Abstract In this work, a photoactive material, Graphdiyne (GDY) loaded with AuNPs (AuNPs-GDY), was successfully synthesized. The fabricated material made use of the natural band-gap structure of GDY, which could produce hole-electron pairs and the plasmon resonance effect of AuNPs to obtain a high photoelectrochemical (PEC) response. AuNPs-GDY PEC response changed with the mass ratio of GDY to tetrachloroauric acid. When the mass ratio of GDY to tetrachloroauric acid was 1:2.5, AuNPs-GDY exhibited the best PEC performance. Thus, the best one was selected as the photoactive material to establish a PEC biosensor for microRNA detection. The PEC biosensor used the alkaline phosphatases as catalyzer to generate ascorbic acid in situ, which provided a low background signal and a high PEC response. The cancer marker, MicroRNA let-7a, was chosen as a target model. Under optimal condition, potential 300 mV and pH 8.0, the PEC biosensor had a detection limit of 3.3 × 10–19 M and a good linearity with microRNA let-7a concentration ranged from 1.0 × 10–18 M to 1.0 × 10−10 M. This PEC biosensor opened a promising platform using GDY to fabricate analytical method and detect microRNA at ultralow levels for diagnoses. Highlights • A novel material, AuNPs-GDY, was firstly synthesized. • SPR effect caused by the AuNPs played a key role in enhancing PEC signals. • A PEC biosensor based on AuNPs-GDY for the let-7a microRNA detection. • The detection limit of 3.3 × 10−19 M was achieved. [ABSTRACT FROM AUTHOR]

This work highlights the use of Fe-modified MgAl-layered double hydroxides (LDHs) to replace dye and semiconductor complexes in dye-sensitized solar cells (DSSCs), forming a layered double hydroxide solar cell (LDHSC). For this purpose, a MgAl-LDH and a Fe-modified MgAl LDH were prepared. X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy were used to analyze the structural properties, morphology, and success of the Fe-modification of the synthesized LDHs. Ultraviolet-visible (UV-Vis) absorption spectroscopy was used to analyze the photoactive behavior of these LDHs and compare it to that of TiO2 and dye-sensitized TiO2. Current-voltage (I–V) solar simulation was used to determine the fill factor (FF), open circuit voltage (VOC), short circuit current (ISC), and efficiency of the LDHSCs. It was shown that the MgFeAl-LDH can act as a simultaneous photoabsorber and charge separator, effectively replacing the dye and semiconductor complex in DSSCs and yielding an efficiency of 1.56%.

Metalloporphyrins are highly recognized for their capacity to act as sensitive substances used in formulation of optical, fluorescent, and electrochemical sensors. A novel compound, namely Pt(II)-5,10,15,20-tetra-(4-allyloxy-phenyl) porphyrin, was synthesized by metalation with PtCl2(PhCN)2 of the corresponding porphyrin base and was fully characterized by UV-vis, fluorimetry, FT-IR, 1H-NMR, and 13C-NMR methods. The fluorescence response of this Pt-porphyrin in the presence of different concentrations of hydrogen peroxide was investigated. Besides, modified glassy carbon electrodes with this Pt-porphyrin (Pt-Porf-GCE) were realized and several electrochemical characterizations were comparatively performed with bare glassy carbon electrodes (GCE), in the absence or presence of hydrogen peroxide. The Pt-porphyrin demonstrated to be a successful sensitive material for the detection of hydrogen peroxide both by fluorimetric method in a concentration range relevant for biological samples (1.05–3.9 × 10−7 M) and by electrochemical method, in a larger concentration range from 1 × 10−6 M to 5 × 10−5 M. Based on different methods, this Pt-porphyrin can cover detection in diverse fields, from medical tests to food and agricultural monitoring, proving high accuracy (correlation coefficients over 99%) in both fluorimetric and electrochemical measurements.

We present results on reversible light-induced solubility of disperse red 1 (DR1) dye in a hydroxypropyl cellulose (HPC) matrix. The samples were prepared by dissolution of both DR1 and HPC in acetone and left to dry overnight in air to form not totally uniform red coatings. It is observed that both heating and illumination of the samples with visible light promote the appearance of a dark red coloration inside the heated or illuminated regions. This new phenomenon is attributed to a dissolution of dye and/or disruption of DR1 aggregates. It is confirmed by visible light and FTIR spectroscopies. UV-Vis spectra evidence disappearance of a band at 400 nm, which is attributed to DR1 aggregates, upon illumination of the samples with visible light. FTIR spectra show new bands at 1600, 1508, and 1342 cm−1 that were assigned to symmetric and asymmetric stretching modes of NO2 of the dissolved DR1. Results evidence a dye solubilization process throughout repeated trans-cis isomery induced by visible light. This process is also a new feature of the light induced molecular movements of azo-dyes and may be used in future for the photo-command of polymer properties and/or light storage. This work opens new perspectives to use natural polymers and composites in photonic applications. It also reveals the strong potential of azo-materials as light powered molecular motors. [ABSTRACT FROM AUTHOR]

The photoactive azobenzenes were intercalated into montmorillonite and beidellite in order to obtain a functional material responsive to UV radiation. The smectite modification involved two steps: (1) intercalation with alkylammonium salts, differing in alkyl chain length, and (2) co-intercalation with azobenzene or aminoazobenzene. The structure and chemistry of the obtained materials were thoroughly characterize with the means of XRD, FTIR, DTA/TG, UV–Vis methods and CHN elemental analysis. The mechanisms interpretation was supported with the molecular dynamics simulations. Photoresponse of the obtained materials was monitored through the observation of the basal spacing shifts upon UV radiation. The results proved that both the type of alkylammonium salt and the host mineral influenced heavily the efficiency of subsequent azobenzene intercalation as well as its photoactive behaviour. The evident and regular photoinduced basal spacing shifts were visible when the density of intercalated salts was low. This was achieved in the BId derivatives due to the low layer charge of the mineral. Also the shorter alkyl chain of the co-intercalated salt promoted larger photoresponses. [ABSTRACT FROM AUTHOR]

Solar energy is considered to be a renewable source of energy that is intrinsically more sustainable than fossil fuels. Developing photoactive hybrid materials to store solar energy has recently received much attention. Herein, a photoactive molecule-graphene oxide hybrid was synthesized and characterized systematically. The solar energy storage performances of the hybrids were studied using various photophysical studies. The energy density and power density of the hybrid materials were 47 WhKg−1 and 156.6 WKg-1 respectively which showed 3 fold higher than the pristine compound. The photoelectrochemical behaviour of the hybrid were also studied using Cyclic voltammetry and Electrochemical impedance spectroscopy (EIS). Results showed the electrochemical performances can be varied due to their changing conformations from trans- to -cis isomerization. This work enables the research community in developing a promising material for solar thermal fuels as well as in energy storage devices. [Display omitted] • AzoF anchored graphene oxide (AzoF-GO) is studied for solar thermal fuels. • The energy density and power density were calculated using Differential Scanning Calorimetry showing higher than pristine. • Photophysical and photoelectrochemical studies suggested AzoF-GO to be a promising energy material. [ABSTRACT FROM AUTHOR]

The aggregation of photoelectrochemical (PEC) active material and biological receptors may affect PEC performances due to limited accessible surface areas. To solve the problem, here we introduced 3D nitrogen-doped graphene hydrogel (3DNGH) into PEC sensing for the first time. 3DNGH not only showed better conductivity than that of 3D graphene due to introducing nirtrogen element into graphene framework, but also provided a high loading amount for PEC active nanomaterial and biological receptors with the porous structure. ZnO/3DNGH was prepared via the hydrothermal treatment. Compared to ZnO/3DGH and ZnO/2DNG, the photocurrent under visible light was greatly improved due to the enhanced light adsorption and accelerated charge transfer. Then ZnO/3DNGH was used to immobilize enzymes to construct a PEC biosensing platform and exhibited good performances. The good result indicated 3DNGH is the promising host for developing PEC biosensors in biomedical and environmental analysis. [ABSTRACT FROM AUTHOR]

In this work, a novel conjugated microporous polymer on carbon nanotube composite (CMP-CNTs) was synthesized as photoelectrochemical (PEC) signal probe to construct sensitive PEC biosensor for sensing N-Gene of COVID-19 by integrating with an ingenious target-trigger T-junction recycling dual-strand displacement amplification (T-DSDA). The CMP-CNTs composites has an ideal photoelectrical conversion efficiency owing to the appearance of a good band matching that can effectively promote electron-hole pairs separation and accelerate carrier migration, thereby generating an extremely high initial photocurrent. Meanwhile, the T-DSDA with superior target conversion efficiency to traditional approaches could convert the small number of targets into extensive output DNAs, leading to the in-situ generation of quench agent N-GQDS decorated nanowires on electrode for significantly reducing initial photocurrent. The results demonstrated that proposed PEC biosensor had a high sensitivity towards N-Gene of COVID-19 and the detection limit was 33 aM, which provided a new way to build the simple, sensitive, and reliable sensing platform for great potential in biological analysis and early clinical diagnosis. [Display omitted] • New CMP-CNTs composites have a good energy band matching, which can boost visible light absorption efficiency. • A target-trigger T-junction dual-strand displacement amplification transform small targets into massive output DNAs. • Output DNAs trigger HCR to generate N-GQDs modified nanowires in situ, which significantly reduces the PEC signal. • The proposed PEC biosensor of CMP-CNTs composites achieved ultra-sensitive detection of N-Gene of COVID-19. [ABSTRACT FROM AUTHOR]

Efficient and rapid detection methods for antibiotics are of great practical importance to achieve environmental safety and protect human health. PEC sensors have been widely employed in antibiotics analysis due to their advantages of low background signal, high sensitivity, simple operation, and wide dynamic response range. This review is focused on the recent progress in photoactivities regulating of inorganic semiconductors from metal oxides/sulfides, metal-based quantum dots to metal-free carbon nitride and various types of PEC sensors in antibiotics monitoring which covers sensing strategies without or with a recognition element (antibody, molecularly imprinted polymer and aptamer). Finally, the challenges and the development prospects of the PEC sensors for antibiotics detection are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

The need for an endless renewable energy supply, typically through the utilization of solar energy in most applications and systems, has driven the expansion, versatility, and diversification of marketed energy storage devices. Energy storage devices such as hybridized dye-sensitized solar cell (DSSC)–capacitors and DSSC–supercapacitors have been invented for energy reservation. The evolution and vast improvement of these devices in terms of their efficiencies and flexibilities have further sparked the invention of the photo-supercapacitor. The idea of coupling a DSSC and supercapacitor as a complete energy conversion and storage device arose because the solar energy absorbed by dye molecules can be efficiently transferred and converted to electrical energy by adopting a supercapacitor as the energy delivery system. The conversion efficiency of a photo-supercapacitor is mainly dependent on the use of active materials during its fabrication. The performances of the dye, photoactive metal oxide, counter electrode, redox electrolyte, and conducting polymer are the primary factors contributing to high-energy-efficient conversion, which enhances the performance and shelf-life of a photo-supercapacitor. Moreover, the introduction of compact layer as a primary adherent film has been earmarked as an effort in enhancing power conversion efficiency of solar cell. Additionally, the development of electrolyte-free solar cell such as the invention of hole-conductor or perovskite solar cell is currently being explored extensively. This paper reviews and analyzes the potential active materials for a photo-supercapacitor to enhance the conversion and storage efficiencies. [ABSTRACT FROM AUTHOR]

Herein, a novel ternary nanocomposite (AuNPs/CdS QDs/CeO 2) with excellent photoelectrochemical (PEC) performance was synthesized as signal probe to construct a near-zero background biosensor for sensitive miRNA-182-5p detection, by integrating with a scrollable three-dimensional (3D) DNA walker mediated cleavage cycling amplification. Impressively, the formation and rolling of scrollable 3D DNA walker triggered by target could realize dynamic, rapid and specific digestion of hairpin DNA on electrode with the aid of Exonuclease III (Exo III), which thus exposed abundant binding sites for assembling stable DNA labeled AuNPs/CdS QDs/CeO 2 nanoprobes. Thanks to the formation of type-II heterojunction (between CeO 2 and CdS QDs) and Schottky junction (generated by CeO 2 and AuNPs), an ideal photoelectric conversion efficiency accompanied with stunningly improved photocurrent was thus acquired for significantly improving the detection sensitivity. It turned out that the detection limit (LOD) of biosensor was ultralow (31 aM). Significantly, the proposed PEC biosensor would exhibit great potential for the composite as a splendid indicator and provide an avenue for constructing the sensing platform with excellent sensitivity and ultralow background. [Display omitted] • AuNPs/CdS QDs/CeO 2 showed admirable photocurrent for the cooperation of type-II heterojunction and Schottky junction. • The scrollable 3D DNA walker as amplifier realized the assembling of abundant signal nanoprobes by high-speed rolling. • The signal generation undergone a process from scratch, presenting a near-zero background to enhance the sensitivity. • This sensor would provide an avenue for developing the methods with excellent sensitivity and ultralow background. [ABSTRACT FROM AUTHOR]

Titanium dental implants are a multibillion dollar market in the United States alone. The growth of a bacterial biofilm on a dental implant can cause gingivitis, implant loss, and expensive subsequent care. Herein, we demonstrate the efficient eradication of dental biofilm on titanium dental implants via swarming magnetic microrobots based on ferromagnetic (Fe 3 O 4 ) and photoactive (BiVO 4 ) materials through polyethylenimine micelles. The ferromagnetic component serves as a propulsion force using a transversal rotating magnetic field while BiVO 4 is the photoactive generator of reactive oxygen species to eradicate the biofilm colonies. Such photoactive magnetically powered, precisely navigated microrobots are able to destroy biofilm colonies on titanium implants, demonstrating their use in precision medicine.

To maximize the efficiency of heterojunction organic photovoltaics (HJOPVs), it is imperative to increase not only the open-circuit voltage ( V) but also the short-circuit current ( I). Therefore, it is desirable to find an organic acceptor material that possesses a higher lowest unoccupied molecular orbital (LUMO) level for higher V and can absorb photons in the solar spectrum efficiently for larger I. In this paper, in comparison with the typical donor poly(3-hexylthiophene) (P3HT) and acceptor [6,6]-phenyl-C-butyric acid ester ([60]PCBM), the geometries, electronic structures, absorption spectra, and transport properties of a series of organic compounds containing 9,9′-bifluorenylidene (9,9′ BF) were systematically investigated using density functional and the semiclassical Marcus charge transfer theory calculation to evaluate their potential severing as acceptor. Our results indicate that the absorption spectra of 99′ BF derivatives have better overlap with the solar spectrum than those of [60]PCBM, and higher LUMOs result in a significant enhancement of V when they are used in HJOPVs with P3HT as donor materials. On the other hand, these compounds own higher electron carrier mobilities comparing with [60]PCBM. The study also demonstrates that the H-shaped compounds based on the 99′ BF backbone possess good photophysical and charge transport properties, can be promising organic semiconductor for heterojunction photovoltaics. [ABSTRACT FROM AUTHOR]

A new optically driven actuator is proposed which utilizes the photoactive nature of a material that exhibits photo-induced phase-transition (PIPT). PIPT changes the material phases reversibly by photo irradiation of certain wavelength. The strain induced by the phase-transition was evaluated in a typical PIPT material, polydiacetylene crystal, as an important characteristic required for an actuator material. Using a thermal heat cycle, the strain induced by the phase-transition was measured to be 1.2, <0.03 and 0.72% at 410 K for the a, b and c axis, respectively. Material deformation using PIPT by single laser pulse was demonstrated for the first time. The observed deflection of the cantilever sample was explained by bimorph formation induced by phase-transition at the photo-irradiated surface. The mechanical response was very fast, less than 5 ms and the sample maintained deformation for more than 60 min. This wireless method will be useful for actuating micro and nanometer mechanical systems which need to move independently from electric wires. [Copyright &y& Elsevier]

This work highlights the use of Fe-modified MgAl-layered double hydroxides (LDHs) to replace dye and semiconductor complexes in dye-sensitized solar cells (DSSCs), forming a layered double hydroxide solar cell (LDHSC). For this purpose, a MgAl-LDH and a Fe-modified MgAl LDH were prepared. X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy were used to analyze the structural properties, morphology, and success of the Fe-modification of the synthesized LDHs. Ultraviolet-visible (UV-Vis) absorption spectroscopy was used to analyze the photoactive behavior of these LDHs and compare it to that of TiO2 and dye-sensitized TiO2. Current-voltage (I–V) solar simulation was used to determine the fill factor (FF), open circuit voltage (VOC), short circuit current (ISC), and efficiency of the LDHSCs. It was shown that the MgFeAl-LDH can act as a simultaneous photoabsorber and charge separator, effectively replacing the dye and semiconductor complex in DSSCs and yielding an efficiency of 1.56%. [ABSTRACT FROM AUTHOR]

Metalloporphyrins are highly recognized for their capacity to act as sensitive substances used in formulation of optical, fluorescent, and electrochemical sensors. A novel compound, namely Pt(II)-5,10,15,20-tetra-(4-allyloxy-phenyl) porphyrin, was synthesized by metalation with PtCl2(PhCN)2 of the corresponding porphyrin base and was fully characterized by UV-vis, fluorimetry, FT-IR, 1H-NMR, and 13C-NMR methods. The fluorescence response of this Pt-porphyrin in the presence of different concentrations of hydrogen peroxide was investigated. Besides, modified glassy carbon electrodes with this Pt-porphyrin (Pt-Porf-GCE) were realized and several electrochemical characterizations were comparatively performed with bare glassy carbon electrodes (GCE), in the absence or presence of hydrogen peroxide. The Pt-porphyrin demonstrated to be a successful sensitive material for the detection of hydrogen peroxide both by fluorimetric method in a concentration range relevant for biological samples (1.05–3.9 × 10−7 M) and by electrochemical method, in a larger concentration range from 1 × 10−6 M to 5 × 10−5 M. Based on different methods, this Pt-porphyrin can cover detection in diverse fields, from medical tests to food and agricultural monitoring, proving high accuracy (correlation coefficients over 99%) in both fluorimetric and electrochemical measurements. [ABSTRACT FROM AUTHOR]

• A novel photoactive material, molybdenum disulfide/graphdiyne, was synthesized. • The inherent reducibility of GDY was used to reduce (NH 4) 2 MoS 4 to MoS 2. • A signal-on PEC method based on dual-modified probe was obtained. • The detection limit was 3.3×10−18 mol/L for microRNA-141. In this study, molybdenum disulfide-graphdiyne (MoS 2 -GDY) was successfully prepared. Utilizing the inherent reducibility of GDY, (NH 4) 2 MoS 4 was reduced to MoS 2 forming photoactive material MoS 2 -GDY complex. MoS 2 -GDY made use of the large band-gap of MoS 2 and the narrow band-gap of GDY. The naturally narrow band-gap of GDY enhanced the absorption of light and the combination of GDY and MoS 2 reduced the electron-hole recombination rate so as to gain strong photoelectrochemical (PEC) signal. The PEC signal of MoS 2 -GDY changed with the mass ratio of GDY to (NH 4) 2 MoS 4. MoS 2 -GDY produced the strongest PEC performance at 1:25. MoS 2 -GDY with the mass ratio of 1:25 was used to fabricate a PEC assay for microRNA-141 detection. To obtain low background noise and strong PEC signal, a dual-modified probe coupling bio-bar code AuNPs and hybridization chain reaction strategy was designed. The dual-modified probe which labeled with MoS 2 -GDY on the one side, and marked with biotin on the other side. And the intensity of PEC depended on the concentration of microRNA-141. Under optimal conditions, 0.2 V potential, pH 7.5, the PEC assay had a linear range in 1.0 × 10−17 mol/L to 1.0 × 10-9 mol/L and a low detection limit of 3.3 × 10-18 mol/L. The assay has been successfully applied to the determination of microRNA-141 in complex biological matrixes. [ABSTRACT FROM AUTHOR]

Herein, novel photoactive materials, nitrogen-doped porous carbon-ZnO (NPC-ZnO) nanopolyhedra, were prepared by direct carbonization of zeolitic imidazolate framework (ZIF)-8 nanopolyhedra in a nitrogen atmosphere. The morphology, structure, and photoelectrochemical (PEC) properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, nitrogen adsorption-desorption method, and PEC methods. The results showed that the obtained NPC-ZnO nanopolyhedra had a rhombic dodecahedron morphology with uniform particle size of about 100 nm and a high surface area of 609.2 m 2 g -1 . Under visible-light irradiation, the NPC-ZnO nanopolyhedra showed better PEC performance than ZnO nanorod and the ZIF-8 nanopolyhedra in aqueous media with dissolved oxygen and ascorbic acid. Taking alkaline phosphatase (ALP) as a model, a NPC-ZnO nanopolyhedra-based PEC sensor was developed and showed good performance for ALP assay with a wide linear response range from 2 to 1500 U L -1 and a low detection limit of 1.7 U L -1 . Moreover, the PEC sensor possessed acceptable selectivity, reproducibility, and stability. The prepared NPC-ZnO nanopolyhedra provide a new photoactive material for the construction of PEC sensors and may have promising applications in PEC assay of heavy metal ions, organic pollutants, and biomolecules.

Solar cells based on organometal halide perovskites have seen rapidly increasing efficiencies, now exceeding 15%. Despite this progress, there is still limited knowledge on the fundamental photophysics. Here we use microwave photoconductance and photoluminescence measurements to investigate the temperature dependence of the carrier generation, mobility, and recombination in (CH3NH3)PbI3. At temperatures maintaining the tetragonal crystal phase of the perovskite, we find an exciton binding energy of about 32 meV, leading to a temperature-dependent yield of highly mobile (6.2 cm(2)/(V s) at 300 K) charge carriers. At higher laser intensities, second-order recombination with a rate constant of γ = 13 × 10(-10) cm(3) s(-1) becomes apparent. Reducing the temperature results in increasing charge carrier mobilities following a T(-1.6) dependence, which we attribute to a reduction in phonon scattering (Σμ = 16 cm(2)/(V s) at 165 K). Despite the fact that Σμ increases, γ diminishes with a factor six, implying that charge recombination in (CH3NH3)PbI3 is temperature activated. The results underline the importance of the perovskite crystal structure, the exciton binding energy, and the activation energy for recombination as key factors in optimizing new perovskite materials.