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Facilitating the separation of photogenerated charges is a crucial process in photocatalytic degradation of pollutants. In this study, Bi2O3/In2O3 composites were prepared using a co-precipitation method and subsequently calcined at 400 ℃ for 1 h. The Mott-Schottky curves confirmed a p(Bi2O3)-n(In2O3) heterojunction was yielded. Due to the significant difference in Fermi levels between Bi2O3 and In2O3, an internal electric field was established at the interface, with field lines directed from In2O3 to Bi2O3. Under illumination, the excited electrons accumulated in the conduction band (CB) of In2O3, while holes gathered in the valence band (VB) of Bi2O3, promoting charge separation and enhancing quantum efficiency. The composite material exhibited the highest photocatalytic activity when the atomic percentage of Bi to In was 1:1, with the first-order reaction rate constant of BI-1 increasing to 0.0149 min−1, which is 4.3 and 4.4 multiples higher than that of pure In2O3 and pure Bi2O3. Recycling experiments demonstrated that the photocatalytic composite possesses good reusability and structural stability.

Designing photocatalysts with p-n heterojunction structures is an effective way to boost the separation of photogenerated carriers and stimulate the photocatalytic degradation activity. Herein, an efficient visible-light responsive AgI/BiSI p-n heterojunction photocatalyst was successfully constructed. X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, and electrochemical measurements confirmed that the AgI/BiSI p-n heterojunction structure was beneficial to the separation and transfer of photogenerated carriers, promoting the generation of main active species (•O2− and h+). Furthermore, the photocatalytic degradation rate constants of Acid Red 1 (0.4699 min−1) and metronidazole (0.0730 min−1) over the optimal AgI/BiSI were about 8.4 and 3.0 times higher than those over pure AgI, respectively. This work provides a heterojunction engineering strategy to design high-efficient photocatalysts for the degradation of refractory organic pollutants.

The development of outstanding high-performance gas sensors for detecting trimethylamine (TMA) gas has attracted broad interest. Herein, novel one dimensional (1D) NiMoO4-functionalized MoO3 nanorods were successfully synthesized by simple two-step hydrothermal and solvothermal routs. The as-synthesized NiMoO4-functionalized MoO3 nanorods exhibit a significantly enhanced TMA sensing properties relative to that of the MoO3 nanorods. The response value of 1-NiMoO4/MoO3 sensor to 10 ppm TMA at 200 °C is 12.1, which is about 2.3 times higher than that of MoO3 sensor (5.5 at 200 °C). In addition, 1-NiMoO4/MoO3 sensor also has high selectivity, good repeatability and stability, sub-ppm-level detection limit (1.6 to 0.3 ppm), fast response recovery speed, and good long-term stability. The outstanding sensing performance of 1-NiMoO4/MoO3 sensor in TMA detection is mainly due to the synergistic effect of unique rod-like structure, substantial resistance modulation effect of heterostructures, strong oxygen adsorption capacity, catalytic effect of the NiMoO4. This work provides an interesting perspective for developing high-performance gas sensor for TMA detection.

Background: Kanamycin (KAN) residues in animal-derived foods continuously enter the human body, which will pose serious threats to human health such as hearing loss, nephrotoxicity and other complications. Therefore, to sensitively detect KAN residues by a reliable technology is extremely urgent in food quality and safety. Compared with traditional methods being limited by cost and complexity, photoelectrochemical (PEC) biosensors benefit from some merits such as rapid response, excellent sensitivity and good stability. In this study, the construction of a highly efficient PEC platform to realize KAN residues detection is discussed., Results: Herein, a novel p-n heterojunction consisting of flower-like BiOI microspheres and graphite carbon nitride (g-C 3 N 4 ) nanoflakes was developed to establish a PEC aptasensor for KAN detection at 0 V. The prepared g-C 3 N 4 /BiOI heterostructure showed not only significantly enhanced PEC activity due to the larger specific surface area but also greatly increased charge separation efficiency owing to the strong internal electric field. Meanwhile, using g-C 3 N 4 /BiOI as a highly efficient photoactive material for binding amine-functionalized aptamers to capture KAN, the photocurrent signals showed a 'turn off' mode to achieve the sensitive detection of KAN. The proposed PEC aptasensor exhibited linear response for KAN from 5 × 10 -9 to 3 × 10 -7  mol L -1 with a low detection limit of 1.31 × 10 -9  mol L -1 , and satisfactory recoveries (97.44-107.38 %) were obtained in real food samples analysis., Significance: This work presented a novel p-n heterojunction-based PEC aptasensor with strong selectivity and stability, rendering it allowed to detect KAN in animal-derived foods including milk, honey and pork. Additionally, the detection range satisfied the MRLs for KAN specified by the national standards, demonstrating the potential application for food analysis. The study provides a new insight into the development of efficient and practical biosensors for antibiotic residues detection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Evaluating the transformer aging state and detecting multi-aging characteristics in transformer oil with high sensitivity and fast speed has become a key challenge. This study introduces a P-N heterojunction (CNTs@NiO-α-Fe 2 O 3 ) fabricated through electroless nickel plating and a one-step hydrothermal method. Additionally, silver nanoparticles (AgNPs) with adjustable particle sizes are grown on the surface using a chemical reduction method. To obtain high sensitivity and rapid SERS signal, CNTs@NiO-α-Fe 2 O 3 -Ag gel is adsorbed on a disposable needle filter (220 nm) surface, and 4-aminothiophene (4-ATP) is grafted onto the surface of SERS substrate. The minimum detection limit was 0.025 mg/L (EF = 5.22 × 10 4 ), and the response time of SERS best signal could be shortened to 3 min. Density functional theory (DFT) calculations reveal that by constructing a P-N heterostructure of NiO-Fe 2 O 3 and assessing the adsorption energies of furfural, acetone, and methanol on the surface of the P-N heterojunction. This SERS strategy has a huge application prospect in the aging diagnosis of oil-paper insulation systems in a transformer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

To boost the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances, the BiOI/graphitic carbon nitride nanotubes (g-C 3 N 4 nanotubes) heterojunction was synthesized herein through the hydrothermal method. BiOI in-situ grew on the surface of g-C 3 N 4 nanotubes derived from melamine. The rapid recombination between photoexcited electrons and holes of pristine semiconductors was prevented via building the stable heterojunction. The SEM results indicated that the BiOI was wrapped around the surface of g-C 3 N 4 nanotubes, resulting in an optimized electronic transmission pathway. Much lower charge transfer resistance at the p-n heterojunction was demonstrated compared with pristine BiOI according to the EIS results, thus leading to the faster surface reaction rates. Moreover, the composite exhibited both outstanding OER and HER activities under illuminated conditions. This study may shed light upon establishing a bifunctional photoelectrocatalysis for photoelectrochemical water splitting based on stable 2D metal and 1D metal-free nanocomposite., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The reutilization of exhausted biochar is attracting extensive interest among researchers. In this study, the biochar generated from Chinese fir with natural regular porous structure that adsorbed Cd 2+ /Ni 2+ at different concentration levels was used as the precursor, and then combined with simple hydrothermal vulcanization and ion deposition to generate the p-n heterojunction between NiS and CdS compounds (NiS-CdS@C) in situ. The hybrids with 3 cycles of NiS deposition reduced the interfacial transmission resistance from 80 Ω to 40 Ω, and increased photocurrent density by 5 times, thus effectively promoting the separation of photogenerated electrons and holes. The simultaneous removal of As(III) and Cr(VI) was selected to evaluate the oxidation and reduction capacity of the visible light/NiS-CdS@C/oxalate system. The results indicated that 10 mg/L As(III) and Cr(VI) were completely and simultaneously removed with 0.75 mM oxalate addition within 40 min in the system, and the NiS-CdS@C presented good durability and stability for oxalate activation. Electron paramagnetic resonance (EPR) and quenching experiments demonstrated that oxalate was activated by holes under light to produce •CO 2 - and enhanced the generation of additional •OH and •O 2 - , further contributing to the oxidation of As(III) and reduction of Cr(VI)., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Green bismuth-based photocatalysts have attracted extensive attention in the field of PPCPs photodegradation. The improved carrier separation efficiency still remains a key factor to enhance photocatalytic performance. Herein, N-doped biomass carbon quantum dots (N-CQDs) decorated p-n heterojunction photocatalyst BiO 2-x /BiOCl was prepared using a facile ion-etching strategy, and it displayed a markedly enhanced catalytic activity in the photodegradation of sulfonamide antibiotics. Calculated by the differential charge density, the doped N-CQDs could gather photogenerated electrons, which indicated that the introduction of N-CQDs into BiO 2-x /BiOCl would effectively inhibit the recombination of photogenerated charge carriers. In addition, photocatalytic performance and density functional theory (DFT) calculation results revealed that the photogenerated electrons tended to transfer from p-BiOCl to n-BiO 2-x through N-CQDs, which could generate ·O 2 - and photogenerated h + to oxidize the target pollutants. Benefiting from the synergistic effect of accelerated separation of e - in p-n heterojunction and the electron-rich performance of N-CQDs, the superb TOC removal efficiencies (89.40% within 120 min visible-light irradiation) and toxicity reduction performance of photodegradation intermediates were achieved. As a consequence, this work will provide a design of high-quality photocatalysts and a green-promising strategy for bismuth-based photocatalysts in the water treatment of PPCPs.+ in p-n heterojunction and the electron-rich performance of N-CQDs, the superb TOC removal efficiencies (89.40% within 120 min visible-light irradiation) and toxicity reduction performance of photodegradation intermediates were achieved. As a consequence, this work will provide a design of high-quality photocatalysts and a green-promising strategy for bismuth-based photocatalysts in the water treatment of PPCPs., (Copyright © 2022 Elsevier B.V. All rights reserved.)

CuO/WO 3 hierarchical hollow microspheres, assembled from irregular two dimensional (2D) nanosheets, were prepared by ultrasonic-wet chemical etching and pyrolysis in this study. The sensing performance of Micro-Electro-Mechanical System (MEMS) xylene gas sensor based on CuO/WO 3 hierarchical structure were evaluated. It was found that the CuO/WO 3 MEMS sensors showed an enhanced gas sensing performance compared with pristine WO 3 sensor. The CuO/WO 3 -3 (the mass ratio of CuO to WO 3 is 3%) sensor exhibited faster response-recover speed and the highest response value to xylene. Moreover, the CuO/WO 3 -3 sensor possessed higher selectivity and long-term stability. The good sensing properties can be attributed to the unique three dimensional (3D) hierarchical structure and p-n heterojunction of CuO-WO 3 . Considering the above advantages, the CuO/WO 3 -3 sensor has a great potential for the rapid detection and monitoring of xylene., (Copyright © 2022. Published by Elsevier B.V.)

Ag 3 PO 4 /BiPO 4 heterojunction photocatalysts with an intergrowth structure composed of sphere-shaped Ag 3 PO 4 and nanorod BiPO 4 were synthesized via a facile combination of solvothermal method and in-situ deposition process. They exhibit enhanced photocatalytic activities under sunlight irradiation, and the heterojunction composite with the 10 wt% loading amounts of Ag 3 PO 4 presented the highest photocatalytic activities against norfloxacin (NFX), ofloxacin (OFXL) and ciprofloxacin (CIP), with high degradation efficiencies of 94.7%, 95.4% and 92.1%, respectively. Additionally, the Ag 3 PO 4 /BiPO 4 photocatalyst demonstrates outstanding structural and photocatalytic stability. The superior performance was attributed to the effective charge transfer across the p-n heterojunction interface and the enhancement of light absorption. This work provides a new insight into the development of novel BiPO 4 -based heterojunction composites and meets the remediation for contaminated aqueous environment., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The unique properties of heterostructure materials make them become a promising candidate for high-performance room-temperature (RT) NO 2 sensing. Herein, a p-n heterojunction consisting of two-dimensional (2D) MoS 2 nanoflakes vertically grown on one-dimensional (1D) SnO 2 nanotubes (NTs) was fabricated via electrospinning and subsequent hydrothermal route. The sulfur edge active sites are fully exposed in the MoS 2 @SnO 2 heterostructure due to the vertically oriented thin-layered morphology features. Moreover, the interface of p-n heterojunction provides an electronic transfer channel from SnO 2 to MoS 2 , which enables MoS 2 act as the generous electron donor involved in NO 2 gas senor detection. As a result, the optimized MoS 2 @SnO 2 -2 heterostructure presents an impressive sensitivity and selectivity for NO 2 gas detection at RT. The response value is 34.67 (R a /R g ) to 100 ppm, which is 26.5 times to that of pure SnO 2. It also exhibits a fast response and recovery time (2.2 s, 10.54 s), as well as a low detection limit (10 ppb) and as long as 20 weeks of stability. This simple fabrication of high-performance sensing materials may facilitate the large-scale production of RT NO 2 gas sensors., (Copyright © 2021 Elsevier B.V. All rights reserved.)

One-dimension Tb 2 O 3 -modified ZnO nanowires were synthesized via water-glycerol binary thermal route. The X-ray diffraction (XRD) patterns demonstrated that the Tb 2 O 3 -modified ZnO was pure phase with high crystallinity. The Energy Dispersive Spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) confirmed the chemical compositions of Tb 2 O 3 -modified ZnO. The images of field-emission electron microscopy (FESEM) indicated that the Tb 2 O 3 -modified ZnO was one-dimension nanowires with a diameter of ∼40-100 nm. N 2 adsorption/desorption measurements and BET analysis were used to revealed the specific surface area and pore size of Tb 2 O 3 -modified ZnO. The images of Transmission Electron Microscope (TEM) and High-Resolution Transmission Electron Microscopy (HRTEM) further showed that the highly uniform heterojunctions had been successfully obtained. The sensitivity and response/recovery time of 3 at% Tb 2 O 3 -modified ZnO tested at 200 °C were ∼123 and 73s/50s to 50 ppm 1,2-propanediol, respectively. In addition, the detection limit was as low as 1 ppm. Under UV irradiation, the sensitivity was further improved to 152 while the response/recovery time was shortened to 67s/23s. The morphology of one-dimension Tb 2 O 3 -modified ZnO nanowires, the increase of oxygen-deficient region in ZnO and the formation of p-n heterojunction enhanced the properties of 1,2-propanediol-sensing synergistically., Competing Interests: Declaration of competing interest The authors declared that they have no conflicts of interest to this work., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Light and electricity are the most prevalent energy sources in natural environment. Herein, a visible-light active Ni foam@NiFe-LDH/Co 3 O 4 composite was successfully prepared by loading 1D Co 3 O 4 nanowires on the surface of 2D NiFe-LDH nanosheets to be a p-n heterojunction supported on the 3D Ni foam through hydrothermal method, which can be used as photoanode directly for photoelectrocatalytic (PEC) process to simultaneously remove bisphenol (BPA) and Cr(VI) from water. This unique Ni foam-based photoanode modified by NiFe-LDH/Co 3 O 4 heterojunction can fully expose the active sites, enhance visible-light absorption and facilitate the migration and separation of photogenerated carriers, thus obtained a boosted efficiency for simultaneous removal of BPA and Cr(VI) under a low applied voltage. Furthermore, the convenient recyclability and excellent stability of the as-prepared Ni foam@NiFe-LDH/Co 3 O 4 also show a great potential in environmental purification., (Copyright © 2020 Elsevier B.V. All rights reserved.)

p-n Heterojunctions of BiOI/ZnO nanorod arrays (BiOI/ZnO NRs) were prepared by loading the p-type BiOI nanosheets on the n-type ZnO nanorod arrays for efficient removal of organic contaminants in water during the piezo-photocatalytic degradation. Under concurrent visible-light irradiation and ultrasonic vibration, the bisphenol solution (50 mL, 10 mg/L) could be completely degraded within 30 min by 10 mg of 0.15 BiOI/ZnO NRs. It shows a dramatically-enhanced degradation efficiency under light irradiation and ultrasonic vibration, which is four times as high as that only under light irradiation. The excellent piezo-photocatalytic ability of BiOI/ZnO NRs could be attributed to the piezoelectric effect coupling with photocatalytic process. Under the irradiation of light, the electron-hole pairs were generated in BiOI nanosheets, and the piezoelectric potential is created inside the highly oriented one-dimensional ZnO nanorods by ultrasonic vibration, which can accelerate the migration of photogenerated carriers. It shows a strategy to effectively enhance the photocatalytic activity through utilizing the internal piezoelectric potential, which is generated by the one-dimensional nanorods with piezoelectric properties under ultrasonic vibration. So, it can promote the separation and prolong the lifetime of photogenerated carriers, and result in high-efficient degradation of organic contaminants., (Copyright © 2020 Elsevier B.V. All rights reserved.)

SnS 2 nanosheets (NSs) have become an ideal candidate for high performance gas sensors due to their unique sensing properties. However, the restacking and aggregation in the process of sensor manufacturing have great influence on the gas sensing performance. In this study, we synthesized a novel heterojunction of the flower-like porous SnS 2 NSs with edge exposed MoS 2 nanospheres via a facile hydrothermal method and sensitive response has achieved at room temperature (27℃). After functionalization, the SMS-Ⅱ showed excellent response (Ra/Rg = 25.9-100 ppm NO 2 ), which is 22.3 times higher than that of the pristine SnS 2 NSs. The sensor also has the characteristics of short response time of 2 s, excellent base line recovery (28.2 s), long-term stability and reliability within 16 weeks, good selectivity and low detection concentration of only 50 ppb. The p-n heterojunction formed between the edge-exposed spherical MoS 2 and the 3D flower-like SnS 2 NSs has a synergistic effect, providing a highly active sites for the adsorption of NO 2 gas, which greatly enhance the sensitivity of the sensor. Simple fabrication and excellent gas sensing performance of the SnS 2 /MoS 2 heterostructure nanomaterials (NMs) will highly effective for commercial gas sensing application., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Here, a novel CuBi 2 O 4 /Bi 2 MoO 6 (CBO/BMO) p-n heterojunction was fabricated and exhibited markedly improved photocatalytic inactivation capacity of E. coli cells under visible light excitation (λ > 420 nm) compared with pure CuBi 2 O 4 and Bi 2 MoO 6 . The CBO/BMO-0.5 hybrid displayed the highest photoinactivation ability which could completely inactivate the E. coli cellswithin 4 h. The mechanism of photocatalytic disinfection towards E. coli of CBO/BMO heterojunctions was attributed to the disruption of cell-membrane, leakage and damage of cellular content including total protein and DNA as verified with SEM, fluorescence-base dead/live stain, sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE) and agarose gel electrophoresis (AGE). Additionally, the scavenge experiments showed that the reactive species h + , e - and •O 2 - play the predominant role in the photocatalytic system of CBO/BMO hybrids. The improved photocatalytic activity of CBO/BMO composites was mainly attributed to the promotion of spatial separation and migration rate of photoproduced electron-hole pairs, enhancement of visible light absorption and more generation of reactive species (•O 2 - ) on the interface of catalyst and water which was demonstrated by nitroblue tetrazolium (NBT) and EPR. Our work indicated that construction of CuBi 2 O 4 /Bi 2 MoO 6 p-n heterostructure photocatalyst is a promising environmental friendly alternative method to deal with the biohazards of pathogenic microorganisms., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this study, a molecularly imprinted polymer photoelectrochemcal (MIP-PEC) sensor based on semiconducting organic polymer dots (Pdots) and inorganic CdS quantum dots (QDs) has been established for the determination of α-Solanine. Specifically, p-type Pdots (p-Pdots) and n-type CdS QDs (n-CdS) were utilized to form organic-inorganic nanoparticles p-n heterojunction to enhance signal response, and their specific energy levels (VB/CB or HOMO/LUMO) were calculated for photoelectrochemical (PEC) bioanalysis application. At the same time, the combination of molecular imprinting technology and photoelectrochemistry overcomes the defeats of photoelectrochemistry which is the absence of selectivity, offers a new MIP-PEC sensor with high sensitivity and excellent selectivity based heterojunction enhanced strategy. In short, this study proposes the semiconducting organic-inorganic nanoparticles p-n heterojunction for molecularly imprinted polymer photoelectrochemcal bioanalysis application, and the MIP-PEC sensor was successfully fabricated based on these materials and methods. In the phosphate buffer solution (PBS), it was clearly observed that the photocurrent has a significant change between elution in acetic acid-ethanol mixture and incubation in template molecular solution because of the faster electron transfer speed, this phenomenon fully showed that the MIP-PEC sensor can specifically detect the target. Thus, the work typically offers a linear range from 0.01 to 1000 ng mL -1 with a detection limit of 6.5 pg mL -1 for α-Solanine. Furthermore, the fabricated MIP-PEC sensor will confirm the actual application., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity., (Copyright © 2014 Elsevier B.V. All rights reserved.)