Heterogeneous p-n Junction CdS/Cu2O Nanorod Arrays: Synthesis and Superior Visible-Light-Driven Photoelectrochemical Performance for Hydrogen Evolution

Self-shedding MOF-nanocarriers modulated CdS/MoSe2 heterojunction activity through in-situ ion exchange: An enhanced split-type photoelectrochemical sensor for deoxynivalenol

Deoxynivalenol (DON), a mycotoxin produced by Fusarium, poses a significant risk to human health and the environment. Therefore, the development of a highly sensitive and accurate detection method is essential to monitor the pollution situation. In response to this imperative, we have devised an advanced split-type photoelectrochemical (PEC) sensor for DON analysis, which leverages self-shedding MOF-nanocarriers to modulate the photoelectric response ability of PEC substrate. The PEC sensing interface was constructed using CdS/MoSe2 heterostructures, while the self-shedding copper peroxide nanodots@ZIF-8 (CPNs@ZIF-8) served as the Cu2+ source for the in-situ ion exchange reaction, which generated a target-related signal reduction. The constructed PEC sensor exhibited a broad linear range of 0.1 pg mL-1 to 500 ng mL-1 with a low detection limit of 0.038 pg mL-1, demonstrating high stability, selectivity, and proactivity. This work not only introduces innovative ideas for the design of photosensitive materials, but also presents novel sensing strategies for detecting various environmental pollutants.

Rational Design of Three Dimensional Hollow Heterojunctions for Efficient Photocatalytic Hydrogen Evolution Applications

The efficiency of photocatalytic hydrogen evolution is currently limited by poor light adsorption, rapid recombination of photogenerated carriers, and ineffective surface reaction rate. Although heterojunctions with innovative morphologies and structures can strengthen built-in electric fields and maximize the separation of photogenerated charges. However, how to rational design of novel multidimensional structures to simultaneously improve the above three bottleneck problems is still a research imperative. Herein, a unique Cu2O─S@graphene oxide (GO)@Zn0.67Cd0.33S Three dimensional (3D) hollow heterostructure is designed and synthesized, which greatly extends the carrier lifetime and effectively promotes the separation of photogenerated charges. The H2 production rate reached 48.5 mmol g-1 h-1 under visible light after loading Ni2+ on the heterojunction surface, which is 97 times higher than that of pure Zn0.67Cd0.33S nanospheres. Furthermore, the H2 production rate can reach 77.3 mmol g-1 h-1 without cooling, verifying the effectiveness of the photothermal effect. Meanwhile, in situ characterization and density flooding theory calculations reveal the efficient charge transfer at the p-n 3D hollow heterojunction interface. This study not only reveals the detailed mechanism of photocatalytic hydrogen evolution in depth but also rationalizes the construction of superior 3D hollow heterojunctions, thus providing a universal strategy for the materials-by-design of high-performance heterojunctions.

A p-n Junction by Coupling Amine-Enriched Brookite-TiO2 Nanorods with CuxS Nanoparticles for Improved Photocatalytic CO2 Reduction

Photocatalytic CO₂ reduction is a promising technology for reaching the aim of "carbon peaking and carbon neutrality", and it is crucial to design efficient photocatalysts with a rational surface and interface tailoring. Considering that amine modification on the surface of the photocatalyst could offer a favorable impact on the adsorption and activation of CO₂, in this work, amine-modified brookite TiO₂ nanorods (NH₂-B-TiO₂) coupled with Cu_xS (NH₂-B-TiO₂-Cu_xS) were effectively fabricated via a facile refluxing method. The formation of a p-n junction at the interface between the NH₂-B-TiO₂ and the Cu_xS could facilitate the separation and transfer of photogenerated carriers. Consequently, under light irradiation for 4 h, when the Cu_xS content is 16%, the maximum performance for conversion of CO₂ to CH₄ reaches at a rate of 3.34 μmol g^-1 h^-1 in the NH₂-B-TiO₂-Cu_xS composite, which is approximately 4 times greater than that of pure NH₂-B-TiO₂. It is hoped that this work could deliver an approach to construct an amine-enriched p-n junction for efficient CO₂ photoreduction.

Magnetic grinding synthesis of copper sulfide-based photocatalytic composites for the degradation of organic dyes under visible light

CuS based composites prepared by magnetic grinding method with metal and sulfur powder as raw materials have photocatalytic activity.

Integrated p-n/Schottky junctions for efficient photocatalytic hydrogen evolution upon Cu@TiO2-Cu2O ternary hybrids with steering charge transfer

Solar-driven photocatalytic H₂ evolution could tackle the issue of fossil fuels-triggered greenhouse gas emission with sustainable clean energy. However, splitting water into hydrogen with high performance by a single semiconductor is challenging because of the poor charge separation efficiency. Herein, a novel ternary Cu@TiO₂-Cu₂O hybrid photocatalyst with multiple charge transfer channels has been designed for efficient solar-to-hydrogen evolution. Indeed, the ternary Cu@TiO₂-Cu₂O hybrid by coupling Cu@TiO₂ with Cu₂O nanoparticles shows highly-efficient photocatalytic hydrogen generation with rate of 12000.6 μmol·g^-1·h^-1, which is 4.4, 2.1, and 1.9 times higher than the pure TiO₂ (2728.8 μmol·g^-1·h^-1), binary Cu@TiO₂ (5595.5 μmol·g^-1·h^-1), and TiO₂-Cu₂O (6076.8 μmol·g^-1·h^-1) composite, respectively. In such a Cu@TiO₂-Cu₂O hybrid, the formed internal electric field in the TiO₂-Cu₂O p-n junction allows the electrons in Cu₂O to migrate to TiO₂, while the electrons in the CB of TiO₂ could flow into Cu via the Schottky junction at the Cu@TiO₂ interface. In this regard, a multiple charge transfer is achieved between the Cu@TiO₂ and Cu₂O, which facilitates promoted charge separation and results in the construction of electron-accumulated center (Cu) and hole-enriched surface (Cu₂O). This p-n/Schottky junctions with steered charge transfer assists the hydrogen production upon the Cu@TiO₂-Cu₂O ternary photocatalyst.

Plasmon-induced hole-depletion layer on p-n heterojunction for highly efficient photoelectrochemical water splitting

The photoelectrocatalytic (PEC) water splitting efficiency of semiconductor photoelectrodes is mainly limited by the effective separation and transfer of photogenerated charges. Zinc indium sulfide-cuprous oxide (ZnIn₂S₄-Cu₂O) p-n heterojunction is constructed to enhance the PEC properties of ZnIn₂S₄. The nickel hydroxide iron oxide (NiFeOOH) layer on the surface of the heterojunction can be used as a hole depletion layer under the induction of plasmon resonance of the most surface silver (Ag) (the holes transferred from Cu₂O valence band to NiFeOOH layer can be excited by Ag to produce hot electron consumption, which makes the last remaining hot holes participate in the water oxidation reaction) to further promote the carrier separation and transfer. The results exhibit that ZnIn₂S₄/Cu₂O/NiFeOOH/Ag photoelectrode with dramatically enhanced photocurrent density of 1.22 mA/cm² at 1.23 V versus the reversible hydrogen electrode (V_RHE), which is 9.4 times higher than the pure ZnIn₂S₄. This work provides a promising concept to design photoelectrodes efficiently in PEC water splitting.

Construction of Ultrafine Ag2S NPs Anchored onto 3D Network Rodlike Bi2SiO5 and Insight into the Photocatalytic Mechanism

A novel three-dimensional (3D) network rodlike Ag₂S/Bi₂SiO₅ photocatalyst with a p-n heterostructure composed of ultrafine Ag₂S nanoparticles (NPs) and Bi₂SiO₅ nanosheets was prepared using an anionic self-regulation strategy by a two-step hydrothermal process. The architecture facilitated the efficient transfer and separation of photogenerated electron-hole pairs. The optimal Ag₂S/Bi₂SiO₅ composite (ABSO_0.10) exhibited an excellent reduction activity (93.5% Cr(VI) removal in wastewater containing 50 mg·L^-1 Cr(VI) within 90 min under visible light), which was about 11.2 and 25.6 times higher than that of the pristine Ag₂S and virgin Bi₂SiO₅, respectively. Assisted by experiments and density functional theory (DFT) calculations, a possible photocatalytic mechanism for Cr(VI) reduction over the Ag₂S/Bi₂SiO₅ composite under visible-light irradiation was proposed.

Composition-dependent activity of ZnxCd1-xSe solid solution coupled with Ni2P nanosheets for visible-light-driven photocatalytic H2 generation

Metal selenide semiconductors have been rarely used for photocatalytic water splitting because of their poor stability and severe photocorrosion properties. Hence, designing stable metal selenides with suitable bandgap energies has considerable practical significance in photocatalytic H₂ evolution. In this work, a novel series of Zn_xCd_1-xSe (x = 0 ∼ 1) with tunable band structure were fabricated through a simple solvothermal method. Impressively, the ZnSe exhibited a maximum H₂ production rate of 1056 µmol g^-1h^-1, which was higher than that of CdSe and Zn_xCd_1-xSe solid solutions. Such visible-light photoactivity for water reduction to H₂ was attained even after 6 cycling photocatalytic experiments. Moreover, the two-dimensional (2D) Ni₂P nanosheets act as a high-efficiency cocatalyst integrated with Zn_xCd_1-xSe semiconductor to boost photocatalytic H₂ generation performance. The optimal 8% Ni₂P/ZnSe composites displayed excellent cycling stability and superior photocatalytic H₂ evolution performance (4336 µmol g^-1h^-1), which was about 4.1 times that of pure ZnSe under visible light irradiation. Photoelectrochemical (PEC), photoluminescence (PL), and time-resolved photoluminescence (TRPL) measurements reveal that the improved photoactivity Ni₂P/ZnSe photocatalysts were ascribed to the effective separation and migration of photoinduced carriers. The present work paves a pathway to explore the fabrication of Zn_xCd_1-xSe solid solutions and the hybridization of 2D transition metal phosphides nanosheets toward photocatalytic applications.

Piezoelectric polarization-induced internal electric field manipulation of the photoelectrochemical performance in Nd, Co codoped BiFeO3

Investigation of the synergistic mechanism of element doping and piezoelectric polarization to improve the catalytic activity of BiFeO3.

One-Dimensional CdS/Carbon/Au Plasmonic Nanoarray Photoanodes via In Situ Reduction-Graphitization Approach toward Efficient Solar Hydrogen Evolution

Photoelectrochemical (PEC) hydrogen evolution has been acknowledged as a promising "green" technique to convert solar energy into clean chemical fuel. Photoanodes play a key role in determining the performance of PEC systems, spurring numerous efforts to develop advanced materials as well as structures to improve the photoconversion efficiency. In this work, we report the rational design of a plasmonic hierarchical nanorod array, composed of oriented one-dimensional (1D) CdS nanorods decorated with a uniformly wrapped graphite-like carbon (C_PDA) layer and Au nanoparticles (Au NPs), as highly efficient photoanode materials. An interfacial in situ reduction-graphitization method has been conducted to prepare the CdS/C_PDA/Au nanoarchitecture, where polydopamine (PDA) coating was used as a C source and a reductant. The CdS/C_PDA/Au nanoarray photoanode demonstrates superior photoconversion efficiency with a photocurrent density of 8.74 mA/cm² and an IPCE value (480 nm) of 30.2% (at 1.23 V vs RHE), under simulated sunlight irradiation, which are 12.7 and 13.5 times higher than pristine CdS. The significant enhancement of PEC performance is mainly benefited from the increase of the entire quantum yield and efficiency due to the formation of a Schottky rectifier, localized surface plasmon resonance (LSPR)-enhanced light absorption, and promoted hot-electron injection from interlayered graphene-like carbon. More importantly, thanks to the inhibited charge carrier recombination process and transferred oxidation reaction sites, the fabricated CdS/C_PDA/Au photoelectrode exhibits lengthened electron lifetimes and better photostability, illustrating its wonderful potential for future PEC application.

CdS-Enhanced Ethanol Selectivity in Electrocatalytic CO2 Reduction at Sulfide-Derived Cu-Cd

The development of Cu-based catalysts for the electrochemical CO₂ reduction reaction (eCO₂ RR) is of major interest for generating commercially important C₂ liquid products such as ethanol. Cu is exclusive among the eCO₂ RR metallic catalysts in that it facilitates the formation of a range of highly reduced C₂ products, with a reasonable total faradaic efficiency but poor product selectivity. Here, a series of new sulfide-derived copper-cadmium catalysts (SD-Cu_x Cd_y ) was developed. An excellent faradaic efficiency of around 32 % but with a relatively low current density of 0.6 mA cm^-2 for ethanol was obtained using the SD-CuCd₂ catalyst at the relatively low overpotential of 0.89 V in a CO₂ -saturated aqueous 0.10 m KHCO₃ solution with an H-cell. The current density increased by an order of magnitude under similar conditions using a flow cell where the mass transport rate for CO₂ was greatly enhanced. Ex situ spectroscopic and microscopic, and voltammetric investigations pointed to the role of abundant phase boundaries between CdS and Cu⁺ /Cu sites in the SD-CuCd₂ catalyst in enhancing the selectivity and efficiency of ethanol formation at low potentials.

Excellent fluorescence detection of Cu2+in water system using N-acetyl-L-cysteines modified CdS quantum dots as fluorescence probe

View of the negative influence of metal ions on natural environment and human health, fast and quantitative detection of metals ions in water systems is significant. Ultra-small grain size CdS quantum dots (QDs) modified with N-acetyl-L-cysteines (NALC) (NALC-CdS QDs) are successfully prepared via a facile hydrothermal route. Based on the changes of fluorescence intensity of NALC-CdS QDs solution after adding metal ions, the fluorescence probe made from the NALC-CdS QDs is developed to detect metal ions in water systems. Among various metal ions, the fluorescence of NALC-CdS QDs effectively quenched by the addition of Cu²⁺, the probe shows high sensitivity and selectivity for detecting Cu²⁺in other interferential metal ions coexisted system. Importantly, the fluorescence intensity of NALC-CdS QDs changes upon the concentration of Cu²⁺, the probe displays an excellent linear relationship between the fluorescence quenching rate and the concentration of Cu²⁺in ranging from 1 to 25μM. Besides, the detected limitation of the probe towards Cu²⁺as low as 0.48μM. The measurement of Cu²⁺in real water sample is also carried out using the probe. The results indicate that NALC-CdS QDs fluorescence probe may be a promising candidate for quantitative Cu²⁺detection in practical application.

NiO Nanosheets Coupled With CdS Nanorods as 2D/1D Heterojunction for Improved Photocatalytic Hydrogen Evolution

Designing low-cost, environment friendly, and highly active photocatalysts for water splitting is a promising path toward relieving energy issues. Herein, one-dimensional (1D) cadmium sulfide (CdS) nanorods are uniformly anchored onto two-dimensional (2D) NiO nanosheets to achieve enhanced photocatalytic hydrogen evolution. The optimized 2D/1D NiO/CdS photocatalyst exhibits a remarkable boosted hydrogen generation rate of 1,300 μmol h-1 g-1 under visible light, which is more than eight times higher than that of CdS nanorods. Moreover, the resultant 5% NiO/CdS composite displays excellent stability over four cycles for photocatalytic hydrogen production. The significantly enhanced photocatalytic activity of the 2D/1D NiO/CdS heterojunction can be attributed to the efficient separation of photogenerated charge carriers driven from the formation of p-n NiO/CdS heterojunction. This study paves a new way to develop 2D p-type NiO nanosheets-decorated n-type semiconductor photocatalysts for photocatalytic applications.

Novel Core-Sheath Cu/Cu2O-ZnO-Fe3O4 Nanocomposites with High-Efficiency Chlorine-Resistant Bacteria Sterilization and Trichloroacetic Acid Degradation Performance

In order to solve two issues of chlorine-resistant bacteria (CRB) and disinfection byproducts (DBPs) in tap water after the chlorine-containing treatment process, an innovative core-sheath nanostructured Cu/Cu₂O-ZnO-Fe₃O₄ was designed and synthesized. The fabrication mechanism of the materials was then systematically analyzed to determine the component and valence state. The properties of CRB inactivation together with trichloroacetic acid (TCAA) photodegradation by Cu/Cu₂O-ZnO-Fe₃O₄ were investigated in detail. It was found that Cu/Cu₂O-ZnO-Fe₃O₄ displayed excellent antibacterial activity with a relatively low cytotoxicity concentration due to its synergism of nanowire structure, ion release, and reactive oxygen species generation. Furthermore, the Cu/Cu₂O-ZnO-Fe₃O₄ nanocomposite also exhibited outstanding photocatalytic degradation activity on TCAA under simulated sunlight irradiation, which was verified to be dominated by the surface reaction through kinetic analysis. More interestingly, the cell growth rate of Cu/Cu₂O-ZnO-Fe₃O₄ was determined to be 50% and 10% higher than those of Cu/Cu₂O and Cu/Cu₂O-ZnO after 10 h incubation, respectively, manifesting a weaker cytotoxicity. Therefore, the designed Cu/Cu₂O-ZnO-Fe₃O₄ could be a promising agent for tap water treatment.

Cu2O nanoparticles sensitize TiO2/CdS nanowire arrays to prolong charge carrier lifetime and highly enhance unassisted photoelectrochemical hydrogen generation with 4.3% efficiency

Effective separation of charge carriers and substantial prolongation of charge carrier lifetime are two vital issues for a photoanode to achieve highly efficient photoelectrochemical (PEC) hydrogen generation. Herein, a Cu₂O-nanoparticle-sensitized TiO₂/CdS (TiO₂/CdS/Cu₂O) nanowire array photoanode is fabricated via subtly combining successive ionic layer adsorption and reaction with a chemical bath deposition method. Both the type-II band alignment with a stair-like structure and a p-n junction are integrated into this ternary photoanode. The fabricated photoanode shows a significant enhancement in the PEC H₂ production with 4.3% efficiency. The measurements of light absorption, photoluminescence and electrochemical spectra undoubtedly demonstrate that the enhanced PEC H₂ generation is ascribed to the remarkable enhancement of visible-light absorbing ability, efficient space charge separation and substantial prolongation of charge carrier lifetime, which are achieved by the synergetic effects of the type-II band alignment with a stair-like structure and the p-n junction. The enhanced PEC H₂ generation demonstrates the potential of the TiO₂/CdS/Cu₂O nanowire arrays as a photoanode to efficiently convert solar energy into chemical fuels.

Using the interfacial barrier effects of p-n junction on electrochemistry for detection of phosphate

A novel type of electrochemical sensor for detection of phosphate in water environment was developed by combining the interfacial barrier of p-n junction with the adsorption of phosphate. The electrochemical response was produced by the induced change of the barrier height, which was only caused by the specific adsorption of phosphate. Two linear concentration ranges (0-0.045 mg L^-1 and 0.045-0.090 mg L^-1) with two sensitivities (4.98 μA (μg L^-1)^-1 and 1.28 μA (μg L^-1)^-1) were found. The good performance made the sensor meet the requirements of the World Health Organization for drinking water (1 mg L^-1 of phosphate). It is an approach to develop electrochemical sensors by employing the interfacial barrier effects on electrochemistry.

Light-Induced Formation of MoOxSy Clusters on CdS Nanorods as Cocatalyst for Enhanced Hydrogen Evolution

Metal and metal-oxide particles are commonly photodeposited on photocatalysts by reduction and oxidation reactions, respectively, consuming charges that are generated under illumination. This study reveals that amorphous MoO_xS_y clusters can be easily photodeposited at the tips of CdS nanorods (NRs) by in situ photodeposition for the first time. The as-prepared MoO_xS_y-decorated CdS samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP) to determine the composition and the possible formation pathways of the amorphous MoO_xS_y clusters. The MoO_xS_y-tipped CdS samples exhibited better hydrogen evolution performance than pure CdS under visible-light illumination. The enhanced activity is attributed to the formation of intimate interfacial contact between CdS and the amorphous MoO_xS_y clusters, which facilitates the charge separation and transfer. Through time-resolved photoluminescence (TRPL) measurements, it was clearly observed that all MoO_xS_y-decorated CdS samples with different loadings of MoO_xS_y showed a faster PL decay when compared to pure CdS, resulting from the effective trapping of photogenerated electrons by the MoO_xS_y clusters. Kelvin probe force microscopy (KPFM) was further used to study the surface potentials of pure CdS NRs and MoO_xS_y-decorated CdS NRs. A higher surface potential on MoO_xS_y-decorated CdS NRs was observed in the dark, indicating that the loading of MoO_xS_y resulted in a lower surface work function compared to pure CdS NRs. This contributed to the effective electron trapping and separation, which was also reflected by the increased photoelectrochemical response. Thus, this study demonstrates the design and facile synthesis of MoO_xS_y-tipped CdS NRs photocatalysts for efficient solar hydrogen production.

Periodic FTO IOs/CdS NRs/CdSe Clusters with Superior Light Scattering Ability for Improved Photoelectrochemical Performance

Periodic fluorine-doped tin oxide inverse opals (FTO IOs) grafted with CdS nanorods (NRs) and CdSe clusters are reported for improved photoelectrochemical (PEC) performance. This hierarchical photoanode is fabricated by a combination of dip-coating, hydrothermal reaction, and chemical bath deposition. The growth of 1D CdS NRs on the periodic walls of 3D FTO IOs forms a unique 3D/1D hierarchical structure, providing a sizeable specific surface area for the loading of CdSe clusters. Significantly, the periodic FTO IOs enable uniform light scattering while the abundant surrounded CdS NRs induce additional random light scattering, combining to give multiple light scattering within the complete hierarchical structure, significantly improving light-harvesting of CdS NRs and CdSe clusters. The high electron collection ability of FTO IOs and the CdS/CdSe heterojunction formation also contribute to the enhanced charge transport and separation. Due to the incorporation of these enhancement strategies in one hierarchical structure, FTO IOs/CdS NRs/CdSe clusters present an improved PEC performance. The photocurrent density of FTO IOs/CdS NRs/CdSe clusters at 1.23 V versus reversible hydrogen electrode reaches 9.2 mA cm^-2 , which is 1.43 times greater than that of CdS NRs/CdSe clusters and 3.83 times of CdS NRs.

Fabrication of the Ni/ZnO/BiOI foam for the improved electrochemical biosensing performance to glucose

The Ni foam decorated with ZnO/BiOI core-shell p-n junction nanorods was prepared and employed as an enzyme loading matrix to detect glucose. The detection potential was decreased significantly (0.3 V) and the sensitivity was enhanced largely (115.2 μA mM^-1 cm^-2). The metal-semiconductor foam can afford the porous surface for loading enzymes and achieving the multiple catalysis. More important, the built-in electric field and electron well in the p-n junction interface provide the driving force for electron transport. It was an effective strategy to enhance the biosensing performance by the rational design of p-n junction.

Bi spheres SPR-coupled Cu2O/Bi2MoO6 with hollow spheres forming Z-scheme Cu2O/Bi/Bi2MoO6 heterostructure for simultaneous photocatalytic decontamination of sulfadiazine and Ni(II)

Environmental problem on the coexistence of organic pollutants and heavy metals in surface waters has become increasingly serious. Few relative researches have focused on their simultaneous decontamination. Herein, a ternary plasmonic Z-scheme Cu₂O/Bi/Bi₂MoO₆ heterojunction was synthesized via two-step route followed by a wet-impregnation, where Bi spheres coupled with Cu₂O particles were anchored on the surface of Bi₂MoO₆ with hollow microflower spheres. The composites were characterized via various measurements. The excellent photocatalytic activity of Cu₂O/Bi/Bi₂MoO₆ displayed in single sulfadiazine (SDZ) oxidation or Ni(II) reduction, and their simultaneous removal. The degradation pathway for SDZ was investigated via LC-MS and Gaussian theory. DFT and FDTD calculations confirmed the electronic structural characteristics in the Cu₂O/Bi/Bi₂MoO₆ heterostructure and the induced electric field enhancement around nearly touching Bi spheres. A possible photodegradation mechanism of the as-prepared photocatalyst was elucidated via combining scavenger experiments with EPR technique. The results suggested h⁺, •O₂^- and •OH all participated in SDZ oxidation, which verified that Z-Scheme electron transfer was major manner in Cu₂O/Bi/Bi₂MoO₆, while •O₂^- and e^-acted on Ni(II) reduction. The improved photocatalytic activity of Cu₂O/Bi/Bi₂MoO₆ could be ascribed to the unique Z-scheme electron transfer among Cu₂O, Bi and Bi₂MoO₆, particularly SPR and local electric field near Bi spheres.

A photoelectrochemical aptasensor based on p-n heterojunction CdS-Cu2O nanorod arrays with enhanced photocurrent for the detection of prostate-specific antigen

A sensitive photoelectrochemical (PEC) aptasensor was constructed for prostate-specific antigen (PSA) detection using an enhanced photocurrent response strategy. The p-n heterostructure CdS-Cu₂O nanorod arrays were prepared on Ti mesh (CdS-Cu₂O NAs/TM) by a simple hydrothermal method and successive ionic-layer adsorption reactions. Compared with the original CdS/TM, the synergistic effect of p-n type CdS-Cu₂O NAs/TM and the internal electric field realizes the effective separation of photoinduced electron-hole pairs and improves the PEC performance. In order to construct the aptasensor, an amino-modified aptamer was immobilized on CdS-Cu₂O NAs/TM to serve as a recognition unit for PSA. After the introduction of PSA, PSA was specifically captured by the aptamer on the PEC aptasensor, which can be oxidized by photogenerated holes to prevent electron-hole recombination and increase photocurrent. Under optimal conditions, the constructed PEC aptasensor has a linear range of 0.1-100 ng·mL^-1 and a detection limit as low as 0.026 ng·mL^-1. The results of aptasensor detection of human serum indicate that it has broad application prospects in biosensors and photoelectrochemical analysis.

p-Type Cu2O as an effective interlayer between CdS and NiOx cocatalysts to promote photocatalytic hydrogen production

A two-step photodeposition method is introduced, aiming to construct a p-type Cu₂O interlayer between n-type CdS and NiO_x cocatalyst. The effect of Cu₂O interlayer is supposed to accelerate the hole transfer from CdS.

Tandem Si Micropillar Array Photocathodes with Conformal Copper Oxide and a Protection Layer by Pulsed Laser Deposition

This work demonstrates the influence of high-quality protection layers on Si-Cu₂O micropillar arrays created by pulsed laser deposition (PLD), with the goal to overcome photodegradation and achieve long-term operation during photoelectrochemical (PEC) water splitting. Sequentially, we assessed planar and micropillar device designs with various design parameters and their influence on PEC hydrogen evolution reaction. On the planar device substrates, a Cu₂O film thickness of 600 nm and a Cu₂O/CuO heterojunction layer with a 5:1 thickness ratio between Cu₂O to CuO were found to be optimal. The planar Si/Cu₂O/CuO heterostructure showed a higher PV performance (J_sc = 20 mA/cm²) as compared to the planar Si/Cu₂O device, but micropillar devices did not show this improvement. Multifunctional overlayers of ZnO (25 nm) and TiO₂ (100 nm) were employed by PLD on Si/Cu₂O planar and micropillar arrays to provide a hole-selective passivation layer that acts against photocorrosion. A micropillar Si/ITO-Au/Cu₂O/ZnO/TiO₂/Pt stack was compared to a planar device. Under optimized conditions, the Si/Cu₂O photocathode with Pt as a HER catalyst displayed a photocurrent of 7.5 mA cm^-2 at 0 V vs RHE and an onset potential of 0.85 V vs RHE, with a stable operation for 75 h.