Photoanode current of large-area MoS₂ ultrathin nanosheets with vertically mesh-shaped structure on indium tin oxide

Highly Wavelength-Selective Self-Powered Solar-Blind Ultraviolet Photodetector Based on Colloidal Aluminum Nitride Quantum Dots

Colloidal quantum dots are semiconductor nanocrystals endowed with unique optoelectronic properties. A major challenge to the field is the lack of methods for synthesizing quantum dots exhibit strong photo-response in the deep-ultraviolet (DUV) band. Here, a facile solution-processed method is presented for synthesizing ultrawide bandgap aluminium nitride quantum dots (AlN QDs) showing distinguished UV-B photoluminescence. Combined with the strong optical response in solar blind band, a solution-processed, self-powered AlN-QDs/β-Ga2O3 solar-blind photodetector is demonstrated. The photodetector is characterized with a high responsivity of 1.6 mA W-1 under 0 V bias and specific detectivity 7.60 × 10-11 Jones under 5 V bias voltage with good solar blind selectivity. Given the solution-processed capability of the devices and extraordinary properties of AlN QDs, this study anticipates the utilization of AlN QDs will open up unique opportunities for cost-effective industrial production of high-performance DUV optoelectronics for large-scale applications.

Two-Dimensional Layered Heterojunctions for Photoelectrocatalysis

Two-dimensional (2D) layered nanomaterial heterostructures, arising from the combination of 2D materials with other low-dimensional species, feature a large surface area to volume ratio, which provides a high density of active sites for catalytic applications and for (photo)electrocatalysis (PEC). Meanwhile, their electronic band structure and high electrical conductivity enable efficient charge transfer (CT) between the active material and the substrate, which is essential for catalytic activity. In recent years, researchers have demonstrated the potential of a range of 2D material interfaces, such as graphene, graphitic carbon nitride (g-C3N4), metal chalcogenides (MCs), and MXenes, for (photo)electrocatalytic applications. For instance, MCs such as MoS2 and WS2 have shown excellent catalytic activity for hydrogen evolution, while graphene and MXenes have been used for the reduction of carbon dioxide to higher value chemicals. However, despite their great potential, there are still major challenges that need to be addressed to fully realize the potential of 2D materials for PEC. For example, their stability under harsh reaction conditions, as well as their scalability for large-scale production are important factors to be considered. Generating heterojunctions (HJs) by combining 2D layered structures with other nanomaterials is a promising method to improve the photoelectrocatalytic properties of the former. In this review, we inspect thoroughly the recent literature, to demonstrate the significant potential that arises from utilizing 2D layered heterostructures in PEC processes across a broad spectrum of applications, from energy conversion and storage to environmental remediation. With the ongoing research and development, it is likely that the potential of these materials will be fully expressed in the near future.

Near-Infrared Organic Photodetectors with Spectral Response over 1200 nm Adopting a Thieno[3,4-c]thiadiazole-Based Acceptor

The nonclassical ten-pi-electron 5,5-fused thieno[3,4-c]thiadiazole (TTD) unit is an excellent building block for constructing sub-silicon-band gap organic semiconductors. However, no small molecule acceptor (SMA) materials based on TTD have been reported despite the fact that high-sensitivity near-infrared organic photodetectors (OPDs) are generally achieved by using SMAs. In this work, we report a TTD-based narrow band gap (0.95 eV) SMA material TTD(DTC-2FIC)2 with strong near-infrared absorption. Employing PTB7-Th as a donor, OPDs based on TTD(DTC-2FIC)2 exhibit an optimized responsivity of 0.095 (±0.007) A W-1 at 1100 nm and sustain a decent responsivity of 0.074 (±0.008) A W-1 at 1200 nm. Moreover, a good specific detectivity over 1 × 1011 Jones is achieved at a wavelength of 1200 nm. Detailed characterizations imply that the performance of TTD(DTC-2FIC)2-based OPDs may be substantially improved by choosing lower-mixing donors with shallower energy levels. This work demonstrates that SMAs incorporating TTD as the core unit hold promise for constructing high-sensitivity sub-silicon-band gap OPDs.

Sheet-Isolated MoS2 Used for Dispersing Pt Nanoparticles and its Application in Methanol Fuel Cells

It is highly challenging to activate the basal plane and minimize the π-π stacking of MoS2 sheets, thus enhancing its catalytic performance. Here, we display an approach for making well-dispersed MoS2 . By using the N-doped multi-walled carbon nanotubes (NMWCNTs) as an isolation unit, the aggregation of MoS2 sheets was effectively reduced, favoring the dispersion of Pt nanoparticles (noted as Pt/NMWCNTs-isolated-MoS2 ). Excellent bifunctional catalytic performance for methanol oxidation and oxygen reduction reaction (MOR/ORR) were demonstrated by the produced Pt/NMWCNTs-isolated-MoS2 . In comparison to Pt nanoparticles supported on MoS2 (Pt/MoS2 ), the MOR activity (2314.14 mA mgpt -1 ) and stability (317.69 mA mgpt -1 after 2 h of operation) on Pt/NMWCNTs-isolatedMoS2 were 24 and 232 times higher, respectively. As for ORR, Pt/NMWCNTs-isolated-MoS2 holds large half-wave potential (0.88 V) and high stability (92.71 % after 22 h of operation). This work presents a tactic for activating the basal planes and reducing the π-π stacking of 2D materials to satisfy their applications in electrocatalysis. In addition, the proposed sheet-isolation method can be used for fabricating other 2D materials to promote the dispersion of nanoparticles, which assist its application in other fields of energy as well as the environment.

Comprehensive Study on Ultra-Wide Band Gap La2O3/ε-Ga2O3 p-n Heterojunction Self-Powered Deep-UV Photodiodes for Flame Sensing

Solar-blind UV photodetectors have outstanding reliability and sensitivity in flame detection without interference from other signals and response quickly. Herein, we fabricated a solar-blind UV photodetector based on a La2O3/ε-Ga2O3 p-n heterojunction with a typical type-II band alignment. Benefiting from the photovoltaic effect formed by the space charge region across the junction interface, the photodetector exhibited a self-powered photocurrent of 1.4 nA at zero bias. Besides, this photodetector demonstrated excellent photo-to-dark current ratio of 2.68 × 104 under 254 nm UV light illumination and at a bias of 5 V, and a high specific detectivity of 2.31 × 1011 Jones and large responsivity of 1.67 mA/W were achieved. Importantly, the La2O3/ε-Ga2O3 heterojunction photodetector can rapidly respond to flames in milliseconds without any applied biases. Based on the performances described above, this novel La2O3/ε-Ga2O3 heterojunction is expected to be a candidate for future energy-efficient fire detection.

Photoelectrocatalytic hydrogen evolution reaction stimulated by the surface plasmon resonance effect of copper and silver surrounded with MoS2

Developing plasmonic metal-based photocatalysts can improve the photoelectrocatalytic hydrogen evolution reaction (HER) and overcome the limitations of semiconductor-based photocatalysts. A MoS2@Ag-Cu foam composite electrode was fabricated on a copper foam and employed for photoelectrocatalytic HER. The optical behavior and photoelectrocatalytic HER test results indicate that the surface plasmon resonance effect of copper and silver is the primary source of light absorption. Additionally, molybdenum sulfide was employed as a hot-electron trap to capture the energetic electrons generated from copper and silver, thereby promoting the hydrogen evolution reaction. Its binder-free electrode exhibits the better HER performance and excellent stability. Low-cost plasmonic metals, copper and silver, were used as the source of photocatalysis, providing a novel perspective for enhancing photoelectrocatalytic HER performance.

A semiconductor-electrocatalyst nano interface constructed for successive photoelectrochemical water oxidation

Photoelectrochemical water splitting has long been considered an ideal approach to producing green hydrogen by utilizing solar energy. However, the limited photocurrents and large overpotentials of the anodes seriously impede large-scale application of this technology. Here, we use an interfacial engineering strategy to construct a nanostructural photoelectrochemical catalyst by incorporating a semiconductor CdS/CdSe-MoS₂ and NiFe layered double hydroxide for the oxygen evolution reaction. Impressively, the as-prepared photoelectrode requires an low potential of 1.001 V vs. reversible hydrogen electrode for a photocurrent density of 10 mA cm^-2, and this is 228 mV lower than the theoretical water splitting potential (1.229 vs. reversible hydrogen electrode). Additionally, the generated current density (15 mA cm^-2) of the photoelectrode at a given overpotential of 0.2 V remains at 95% after long-term testing (100 h). Operando X-ray absorption spectroscopy revealed that the formation of highly oxidized Ni species under illumination provides large photocurrent gains. This finding opens an avenue for designing high-efficiency photoelectrochemical catalysts for successive water splitting.

Flexible assembly of the PEDOT: PSS/ exfoliated β-Ga2O3 microwire hybrid heterojunction for high-performance self-powered solar-blind photodetector

Motivated by the goals of fabricating highly reliable, high performance, and cost-efficient self-powered photodetector (PD) for numerous scientific research and civil fields, an organic-inorganic hybrid solar-blind ultraviolet (UV) PD based on PEDOT: PSS/exfoliated β-Ga₂O₃ microwire heterojunction was fabricated by a flexible and cost-effective assembly method. Benefiting from the heterojunction constructed by the highly crystalline β-Ga₂O₃ and the excellent hole transport layer PEDOT: PSS, the device presents a high responsivity of 39.8 mA/W at 250 nm and a sharp cut-off edge at 280 nm without any power supply. Additionally, the ultra-high normalized photo-to-dark current ratio (> 10⁴ mW^-1cm²) under reverse bias and the superior detectivity of 2.4×10¹² Jones at zero bias demonstrate the excellent detection capabilities. Furthermore, the hybrid PD exhibits a rapid rise time (several milliseconds) and high rejection ratio (R₂₅₀/R₃₆₅: 5.8 × 10³), which further highlights its good spectral selectivity for solar-blind UV. The prominent performance is mainly ascribed to the efficient separation of the photogenerated carriers by the large built-in electric field of the advanced heterojunction. This flexible assembly strategy for solar-blind UV PD combines the advantages of high efficiency, low cost and high performance, providing more potential for PD investigation and application in the future.

6-Aza-2-thio-thymine-gold nanoclusters: an excellent candidate in the photoelectrochemical field

The high performance of the photoelectrochemical (PEC) properties of AuNCs can be achieved with 6-aza-2-thio-thymine-AuNCs (ATT-AuNCs) as a photoactive material. The ATT-AuNCs yielded a cathodic photocurrent density as high as 88 μA cm^-2 with O₂ as electron acceptor, which is three orders of magnitude higher than those of other AuNCs in aqueous solutions. Moreover, ATT-AuNCs also show a higher carrier density, shorter Debye length, and smaller depletion layer width than those of reported AuNCs. This work not only reveals the PEC performance and mechanism of ATT-AuNCs, but also establishes a framework for in-depth design and studying the PEC performance of AuNCs.

Highly Conductive Ligand-Free Cs2 PtBr6 Perovskite Nanocrystals with a Narrow Bandgap and Efficient Photoelectrochemical Performance

Design of high-performance all-inorganic halide perovskites, especially lead-free perovskites, is key to the broadening of its application prospects. Herein, the authors report the synthesis of ligand-free cesium platinum (IV) bromide nanocrystals (Cs₂ PtBr₆ NCs), a new kind of vacancy-ordered lead-free perovskite nanomaterial, by a facile one-pot method. The Cs₂ PtBr₆ NCs exhibits a narrow band gap of 1.32 eV covering the entire visible range, which is supported by density functional theory calculations. Together with their high conductivity, matching energy levels with the work function of carbon electrodes, and excellent environmental stability, this NC displays a cathodic photocurrent density as high as 335 µA cm^-2 , two orders of magnitude higher than other perovskites in aqueous solutions without the need of other electron acceptors. These combined properties suggest that the Cs₂ PtBr₆ NCs have great potentials in a wide range of photoelectronic and photoelectrochemical sensing applications.

Electrochemiluminescent determination of prostate-specific antigen using Au@(MoS2/GO/o-MWNTs) nanohybrids as co-reaction accelerator and hyperbranched hybridization chain reaction for signal amplification

Three-dimensional flowerlike Au@(MoS₂/GO/o-MWNTs) nanohybrids (abbreviated as AMGMs) were synthesized and then introduced into an electrochemiluminescence (ECL) system as a new co-reaction accelerator for the ultrasensitive prostate-specific antigen (PSA). The AMGMs not only served as a substrate with good conductivity and a large specific surface area for loading abundant primary antibodies but also acted as an effective co-reaction accelerator; the co-reaction accelerator could interact with a co-reactant rather than the luminophore to boost the generation of free radical intermediates, thereby producing abundant excited states of luminophores to amplify the ECL signal response. Additionally, an anticipated signal amplification strategy based on the hybridization chain reaction (HCR) was developed by gathering a large amount of a DNA initiator on gold nanoparticles. These gathered DNA initiators could generate multiple DNA concatemers and attach more signal molecules, which resulted in outstanding exponential signal amplification. Consequently, the ECL immunosensor demonstrated high sensitivity, with a linear range from 0.1 pg mL^-1 to 50 ng mL^-1 and a detection limit of 0.028 pg mL^-1. In addition, the immunosensor displayed excellent stability and selectivity. It was evaluated by analyzing human serum sample. The recovery obtained was 98.80-112.00% and the RSD was 1.73-3.12%, indicating the immunosensor could be applied to the simultaneous detection of PSA in human serum samples. Graphical abstract.

Recent Progress in LDH@Graphene and Analogous Heterostructures for Highly Active and Stable Photocatalytic and Photoelectrochemical Water Splitting

Photocatalytic (PC) and photoelectrochemical (PEC) water splitting is a plethora of green technological process, which transforms copiously available photon energy into valuable chemical energy. With the augmentation of modern civilization, developmental process of novel semiconductor photocatalysts proceeded at a sweltering rate, but the overall energy conversion efficiency of semiconductor photocatalysts in PC/PEC is moderately poor owing to the instability ariseing from the photocorrosion and messy charge configuration. Particularly, layered double hydroxides (LDHs) as reassuring multifunctional photocatalysts, turned out to be intensively investigated owing to the lamellar structure and exceptional physico-chemical properties. However, major drawbacks of LDHs material are its low conductivity, sluggish mass transfer and structural instability in acidic media, which hinder their applicability and stability. To surmount these obstacles, the formation of LDH@graphene and analogus heterostructures could proficiently amalgamate multi-functionalities, compensate distinct shortcomings, and endow novel properties, which ensure effective charge separation to result in stability and superior catalytic activities. Herein, we aim to summarize the currently updated synthetic strategies used to design heterostructures of 2D LDHs with 2D/3D graphene and graphene analogus material as graphitic carbon nitride (g-C₃ N₄ ), and MoS₂ as mediator, or interlayer support, or co-catalyst or vice versa for superior PC/PEC water splitting activities along with long-term stabilities. Furthermore, latest characterization technique measuring the stability along with variant interface mode for imparting charge separation in LDH@graphene and graphene analogus heterostructure has been identified in this field of research with understanding the intrinsic structural features and activities.

Noble-Metal-Free Multicomponent Nanointegration for Sustainable Energy Conversion

Global energy and environmental crises are among the most pressing challenges facing humankind. To overcome these challenges, recent years have seen an upsurge of interest in the development and production of renewable chemical fuels as alternatives to the nonrenewable and high-polluting fossil fuels. Photocatalysis, photoelectrocatalysis, and electrocatalysis provide promising avenues for sustainable energy conversion. Single- and dual-component catalytic systems based on nanomaterials have been intensively studied for decades, but their intrinsic weaknesses hamper their practical applications. Multicomponent nanomaterial-based systems, consisting of three or more components with at least one component in the nanoscale, have recently emerged. The multiple components are integrated together to create synergistic effects and hence overcome the limitation for outperformance. Such higher-efficiency systems based on nanomaterials will potentially bring an additional benefit in balance-of-system costs if they exclude the use of noble metals, considering the expense and sustainability. It is therefore timely to review the research in this field, providing guidance in the development of noble-metal-free multicomponent nanointegration for sustainable energy conversion. In this work, we first recall the fundamentals of catalysis by nanomaterials, multicomponent nanointegration, and reactor configuration for water splitting, CO₂ reduction, and N₂ reduction. We then systematically review and discuss recent advances in multicomponent-based photocatalytic, photoelectrochemical, and electrochemical systems based on nanomaterials. On the basis of these systems, we further laterally evaluate different multicomponent integration strategies and highlight their impacts on catalytic activity, performance stability, and product selectivity. Finally, we provide conclusions and future prospects for multicomponent nanointegration. This work offers comprehensive insights into the development of cost-competitive multicomponent nanomaterial-based systems for sustainable energy-conversion technologies and assists researchers working toward addressing the global challenges in energy and the environment.

Rhenium Doping of Layered Transition-Metal Diselenides Triggers Enhancement of Photoelectrochemical Activity

The ever decreasing sources of fossil fuels have launched extensive research of alternative materials that might play a key role in their replacement. Therefore, the scientific community continuously investigates the possibilities of maximizing the working capacity of such materials in order to fulfill energy challenges in the near future. In this context, doping of the semiconducting materials is a versatile strategy to trigger their physicochemical properties as well their electrochemical performance. Herein, the impact of rhenium doping toward photoelectrochemical activity of MoSe₂ and WSe₂ was studied. Our results indicate that rhenium as a dopant contributes to better overall electrochemical performance, that is, an easier electron transfer of these materials compared to pristine compounds. Additionally, the photoelectrochemical measurements revealed that the doping with rhenium generated an enhancement of the photocurrent response of MoSe₂ as well as WSe₂ under UV light illumination.

Signal-on cathodic photoelectrochemical aptasensing of insulin: Plasmonic Au activated amorphous MoSx photocathode coupled with target-induced sensitization effect

Cathodic photoelectrochemical (PEC) bioassay is more resistant to reductive interferents, and development of high-performance photocathode is imperatively required in precise monitoring target in complex matrices. In this work, a plasmonic Au activated amorphous MoS_x photocathode (a-MoS_x/Au) was fabricated by sequential electrodeposition. Coupled with a sensitization amplification strategy induced by target-aptamer recognition, an ultrasensitive and high-affinitive signal-on cathodic PEC aptasensor for insulin detection was developed. Under optimum conditions, the sensor exhibits a wide linear range (0.1 pg/mL~100 ng/mL) and an ultralow detection limit (28 fg/mL) even lower than most sensors reported so far. Plasmonic Au activation and target-induced sensitization effect are responsible for high-performance PEC aptasensing of insulin at a-MoS_x photocathode.

Reusable, few-layered-MoS2 nanosheets/graphene hybrid on cellulose paper for superior adsorption of methylene blue dye

High efficient methylene blue adsorption by MoS₂ micro-flowers on graphene-cellulose paper.

Ultrasensitive, Superhigh Signal-to-Noise Ratio, Self-Powered Solar-Blind Photodetector Based on n-Ga2O3/p-CuSCN Core-Shell Microwire Heterojunction

Solar-blind photodetectors have captured intense attention due to their high significance in ultraviolet astronomy and biological detection. However, most of the solar-blind photodetectors have not shown extraordinary advantages in weak light signal detection because the forewarning of low-dose deep-ultraviolet radiation is so important for the human immune system. In this study, a high-performance solar-blind photodetector is constructed based on the n-Ga₂O₃/p-CuSCN core-shell microwire heterojunction by a simple immersion method. In comparison with the single device of the Ga₂O₃ and CuSCN, the heterojunction photodetector demonstrates an enhanced photoelectric performance with an ultralow dark current of 1.03 pA, high photo-to-dark current ratio of 4.14 × 10⁴, and high rejection ratio (R₂₅₄/R₃₆₅) of 1.15 × 10⁴ under a bias of 5 V. Excitingly, the heterostructure photodetector shows high sensitivity to the weak signal (1.5 μW/cm²) of deep ultraviolet and high-resolution detection to the subtle change of signal intensity (1.0 μW/cm²). Under the illumination with 254 nm light at 5 V, the photodetector shows a large responsivity of 13.3 mA/W, superb detectivity of 9.43 × 10¹¹ Jones, and fast response speed with a rise time of 62 ms and decay time of 35 ms. Additionally, the photodetector can work without an external power supply and has specific solar-blind spectrum selectivity as well as excellent stability even through 1 month of storage. Such prominent photodetection, profited by the novel geometric construction and the built-in electric field originating from the p-n heterojunction, meets greatly well the "5S" requirements of the photodetector for practical application.

Structural and optical properties of penicillamine-protected gold nanocluster fractions separated by sequential size-selective fractionation

Polydisperse water-soluble gold nanoclusters (AuNCs) protected by penicillamine have been synthesized in this work. The sequential size-selective precipitation (SSSP) technique has been applied for the size fractionation and purification of the monolayer-protected AuNCs. Through continuously adding acetone to a crude AuNC aqueous solution and controlling the volume percentage of acetone, we successfully separated the polydisperse AuNCs with diameters ranging from 0.5 to 5.4 nm into four different fractions sequentially. High-resolution transmission electron microscopy (HRTEM) shows that the four fractions are well-dispersed spherical particles of diameter 3.0 ± 0.6, 2.3 ± 0.5, 1.7 ± 0.4, and 1.2 ± 0.4 nm. Proton nuclear magnetic resonance spectroscopy suggests that disulfide, excess ligands and gold(I) complexes were removed from the AuNCs fractions. These results demonstrate the considerable potential of the SSSP technique for size-based separation and purification of AuNCs, achieving not only the isolation of larger nanoclusters (NCs) from small NCs in a continuous fashion, but also for the removal of small-molecule impurities. Based on the results from the mass spectrometry and thermogravimetric analysis, the average composition of the four fractions can be represented by Au₃₈(SR)₁₈, Au₂₈(SR)₁₅, Au₁₈(SR)₁₂, and Au₁₁(SR)₈, respectively. This indicates that the SSSP separation is mainly dependent on the core size and the ratio of Au atoms to ligands of AuNCs. X-ray photoelectron spectroscopy (XPS) has also been applied to observe the molecular dependence on the gold and sulfur chemical state of organosulfur monolayers of the fractions. The photoluminescence spectra of these AuNCs in the range of 900-790 nm was investigated at room temperature. The results show that the peak emission energy of the size-selected AuNCs undergoes a blue shift when the size is decreased, which can be attributed to the quantum confinement effect.

Ultrathin MoS2 nanosheets for high-performance photoelectrochemical applications via plasmonic coupling with Au nanocrystals

In this work, we prepared ultrathin MoS2 nanosheets with exposed active edge sites and high electric conductivity that can sufficiently absorb light in the visible region to enable solar energy conversion. The gold nanocrystal-decorated MoS2 nanosheets facilitate sufficiently enhanced photoelectrochemical water splitting in the UV-visible region. Different Au nanostructures, such as Au nanoparticles and nanorods, were modified on the surface of MoS2 nanosheets to promote photoelectrochemical water decomposition. By spin-coating a synthetic gold-modified MoS2 hybrid photoanode on a FTO substrate, the efficiency of photoelectrochemical water oxidation was significantly enhanced, by 2 times (nanorods) and 3.5 times (nanoparticles) in the visible-infrared region; furthermore, the average optical resistance was reduced by a factor of two compared to the MoS2 photoanode without Au, and the photocurrent increases exponentially when the system bias was greater than 0.7 volts. The Au-MoS2 metal-semiconductor interface plays an important role in studying the surface plasmon interactions, charge transfer mechanism, and electric field amplification. This rational design for such a unique hybrid nanostructure explains the plasmon-enhanced photoelectrochemical water splitting. This current contribution provides a new path for using the plasmonic metal/semiconductor heterostructure to effectively harvest UV-visible light for solar fuel generation.

Au nanoparticles on two-dimensional MoS2 nanosheets as a photoanode for efficient photoelectrochemical miRNA detection

MiRNAs are small regulatory RNAs that play crucial roles in the oncogenic state in various cancers and have shown highly promising clinical applications as plasma-based markers for cancer classification and prognostication. Due to their electroanalytical advantages, photoelectrochemical biosensors are a very attractive alternative technology for miRNA sensing and detection. In this work, we demonstrated a novel photoelectrochemical (PEC) sensor using the in situ grown Au nanoparticles/two-dimensional molybdenum disulfide (MoS2) nanosheet heterojunction (MoS2-AuNPs) on ITO glass as the photoanode (MoS2-AuNPs/ITO). AuNPs were used as a photoelectronic transfer promoter and DNA probe immobilization carrier as well. The thiol modified biotin DNA with a hairpin structure was tethered to the MoS2-AuNPs/ITO surface to form a specific capturing layer for miRNA detection. The biotin specific protein streptavidin was used as the signal amplifying species. This PEC sensor is structurally simple and possesses sensitivity and specificity toward miRNA. The CV and EIS responses were evaluated to monitor the PEC anode fabrication. The stability and reproducibility of this PEC design strategy were both evaluated before it was used in analyzing the samples of miRNA in human serum. Finally, we found that this PEC sensor displayed a broad detection linear range and a low detection limit of 4.21 fM, and it can excellently discriminate the mismatched miRNA. These findings pave the way for developing PEC sensors targeting miRNA by using noble metals/MoS2 heterojunctions.

In situ formation of spherical MoS2 nanoparticles for ultra-low friction

The motion resistance and energy dissipation of rolling friction are much lower than those of sliding friction at the macroscale. But at the microscale, the impact of rolling on friction remains an open question. Here, we show that spherical MoS2 nanoparticles can be formed in situ at a friction interface by scrolling and wrapping MoS2 nanosheets under the induction of a reciprocating shear stress, when an MoS2 coating constructed from loosely stacked nanosheets is tested in a vacuum of 3.5 × 10-3 Pa. An ultra-low friction state can be readily realized with friction coefficients of 0.004-0.006, which are one order of magnitude lower than that of a pulse laser deposited MoS2 coating without nanoparticles formed in a friction process. Accordingly, the spherical nanoparticles are highlighted as the key factor in the ultra-low friction. Classical molecular dynamics simulations further reveal that the motion mode of the MoS2 nanoparticle is stress-dependent. This finding confirms access to ultra-low friction by introducing rolling friction based on the microstructural evolution of the coating.

A Real-Time Wearable UV-Radiation Monitor based on a High-Performance p-CuZnS/n-TiO2 Photodetector

Solar radiation, especially ultraviolet (UV) light, is a major hazard for most skin-related cancers. The growing needs for wearable health monitoring systems call for a high-performance real-time UV sensor to prevent skin diseases caused by excess UV exposure. To this end, here a novel self-powered p-CuZnS/n-TiO₂ UV photodetector (PD) with high performance is successfully developed (responsivity of 2.54 mA W^-1 at 0 V toward 300 nm). Moreover, by effectively replacing the Ti foil with a thin Ti wire for the anodization process, the conventional planar rigid device is artfully turned into a fiber-shaped flexible and wearable one. The fiber-shaped device shows an outstanding responsivity of 640 A W^-1 , external quantum efficiency of 2.3 × 10⁵ %, and photocurrent of ≈4 mA at 3 V, exceeding those of most current UV PDs. Its ultrahigh photocurrent enables it to be easily integrated with commercial electronics to function as a real-time monitor system. Thus, the first real-time wearable UV radiation sensor that reads out ambient UV power density and transmits data to smart phones via wifi is demonstrated. This work not only presents a promising wearable health monitor, but also provides a general strategy for designing and fabricating smart wearable electronic devices.

Flaky nano-crystalline SnSe2 thin films for photoelectrochemical current generation

We report chemical vapor deposition (CVD) and photoelectrochemical properties of large-area thin films of nano-crystalline SnSe₂ on conducting FTO glass. We show that densely packed, randomly oriented SnSe₂ nanoflakes can be grown by reacting vapors of tin monoselenide (SnSe) and selenium at 550 °C without compromising the electrical properties of FTO. We demonstrate that SnSe₂/FTO is photoelectrochemically active in visible to near-UV wavelengths (350–700 nm) and exhibits incident-photon-to-current-efficiency (IPCE) as high as 3.7% at 0 V versus the Ag/AgCl/1 M KCl reference electrode under 350 nm light illumination.

We report chemical vapor deposition (CVD) and photoelectrochemical properties of large-area thin films of nano-crystalline SnSe₂ on conducting FTO glass.

Photoelectric response properties under UV/red light irradiation of ZnO nanorod arrays coated with vertically aligned MoS2 nanosheets

MoS₂ with layered structure and distinct physical properties has attracted attention for electronic or optoelectronic devices. The photoelectric response properties of MoS₂/ZnO heterojunctions based devices fabricated by spin-coating MoS₂ nanosheets solutions on ZnO nanorod arrays (NRs) were investigated. The results revealed that MoS₂ nanosheets were vertically aligned on the surface of ZnO NRs and the devices exhibit good photoresponse stability and reproducibility under UV and red light illuminations. The vertically aligned MoS₂ nanosheets facilitate the fast photogenerated carrier separation and transport. The devices with few-layered MoS₂ nanosheets show a high responsivity and detectivity under UV and red light illuminations, which can be attributed to small contact resistance between MoS₂ nanosheets and ZnO NRs. These results provide important insights in the facile fabrication strategy and understanding electronic and optoelectronic devices based on the heterostructures with vertically aligned MoS₂.

Superior Adsorption and Regenerable Dye Adsorbent Based on Flower-Like Molybdenum Disulfide Nanostructure

Herein we report superior dye-adsorption performance for flower-like nanostructure composed of two dimensional (2D) MoS₂ nanosheets by a facile hydrothermal method, more prominent adsorption of cationic dye compared with anodic dye indicates the dye adsorption performance strongly depends on surface charge of MoS₂ nanosheets. The adsorption mechanism of dye is analyzed, the kinetic data of dye adsorption fit well with the pseudo-second-order model, meanwhile adsorption capability at different equilibrium concentrations follows Langmuir model, indicating the favorability and feasibility of dye adsorption. The regenerable property for MoS₂ with full adsorption of dye molecules by using alkaline solution were demonstrated, showing the feasibility of reuse for the MoS₂, which is promising in its practical water treatment application.

Enhanced Electrocatalytic Activity for Water Splitting on NiO/Ni/Carbon Fiber Paper

Large-scale growth of low-cost, efficient, and durable non-noble metal-based electrocatalysts for water splitting is crucial for future renewable energy systems. Atomic layer deposition (ALD) provides a promising route for depositing uniform thin coatings of electrocatalysts, which are useful in many technologies, including the splitting of water. In this communication, we report the growth of a NiO/Ni catalyst directly on carbon fiber paper by atomic layer deposition and report subsequent reduction and oxidation annealing treatments. The 10-20 nm NiO/Ni nanoparticle catalysts can reach a current density of 10 mA·cm-2 at an overpotential of 189 mV for hydrogen evolution reactions and 257 mV for oxygen evolution reactions with high stability. We further successfully achieved a water splitting current density of 10 mA·cm-2 at 1.78 V using a typical NiO/Ni coated carbon fiber paper two-electrode setup. The results suggest that nanoparticulate NiO/Ni is an active, stable, and noble-metal-free electrocatalyst, which facilitates a method for future water splitting applications.

Improving the Photoelectric Characteristics of MoS2 Thin Films by Doping Rare Earth Element Erbium

We investigated the surface morphologies, crystal structures, and optical characteristics of rare earth element erbium (Er)-doped MoS₂ (Er: MoS₂) thin films fabricated on Si substrates via chemical vapor deposition (CVD). The surface mopography, crystalline structure, light absorption property, and the photoelectronic characteristics of the Er: MoS₂ films were studied. The results indicate that doping makes the crystallinity of MoS₂ films better than that of the undoped film. Meanwhile, the electron mobility and conductivity of the Er-doped MoS₂ films increase about one order of magnitude, and the current-voltage (I-V) and the photoelectric response characteristics of the Er:MoS₂/Si heterojunction increase significantly. Moreover, Er-doped MoS₂ films exhibit strong light absorption and photoluminescence in the visible light range at room temperature; the intensity is enhanced by about twice that of the undoped film. The results indicate that the doping of MoS₂ with Er can significantly improve the photoelectric characteristics and can be used to fabricate highly efficient luminescence and optoelectronic devices.

Etching treatment of vertical WO3 nanoplates as a photoanode for enhanced photoelectrochemical performance

An innovative etching method was developed to increase surface voids, active crystal facets and surface groups, which led to improved photocurrent performance.

Facile one-pot synthesis of MoS2 quantum dots-graphene-TiO2 composites for highly enhanced photocatalytic properties

We reported a simple one-pot solvothermal approach to fabricate a MoS2 quantum dots (QDs)-graphene-TiO2 (MGT) composite photocatalyst with significantly improved photocatalysis properties, which is caused by the increased charge separation, visible-light absorbance, specific surface area and reaction sites upon the introduction of MoS2 QDs.

Photogeneration of hydrogen from water by hybrid molybdenum sulfide clusters immobilized on titania

Two new hybrid molybdenum(IV) Mo3 S7 cluster complexes derivatized with diimino ligands have been prepared by replacement of the two bromine atoms of [Mo3 S7 Br6 ](2-) by a substituted bipyridine ligand to afford heteroleptic molybdenum(IV) Mo3 S7 Br4 (diimino) complexes. Adsorption of the Mo3 S7 cores from sample solutions on TiO2 was only achieved from the diimino functionalized clusters. The adsorbed Mo3 S7 units were reduced on the TiO2 surface to generate an electrocatalyst that reduces the overpotential for the H2 evolution reaction by approximately 0.3 V (for 1 mA cm(-2) ) with a turnover frequency as high as 1.4 s(-1) . The nature of the actual active molybdenum sulfide species has been investigated by X-ray photoelectron spectroscopy. In agreement with the electrochemical results, the modified TiO2 nanoparticles show a high photocatalytic activity for H2 production in the presence of Na2 S/Na2 SO3 as a sacrificial electron donor system.