Heterojunction Composites Research Articles

Solution-processed bulk heterojunction broadband photodetectors based on perovskites incorporated with PbSe quantum dots

Broadband photodetectors (PDs) have great applications in both scientific and industrial sectors. In this study, we report room-temperature operated solution-processed bulk heterojunction (BHJ) broadband PDs based on perovskites incorporated with highly electrically conductive PbSe quantum dots (QDs). The p-type perovskites incorporated with the n-type PbSe QDs forming the BHJ composite thin film not only extend the spectral response up to the infrared region but also balance charge transport of the photoactive layer, resulting in boosted photocurrent and suppressed dark current, consequently, enhanced device performance of the broadband PDs. As a result, the solution-processed BHJ broadband PDs exhibit a responsibility of 10 mA/W, a detectivity of 10 11 Jones (1 Jones = 1 cm ⋅ Hz 1/2 /W), and a linear dynamic range of 53 dB in the spectral response ranging from 350 nm to 2500 nm, where the BHJ broadband PDs are operated at room temperature. These studies indicate that we provide a facile way to develop room-temperature operated solution-processed broadband PDs. • High electrically conductive n-type PbSe quantum dots and p-type CH 3 NH 3 PbI 3 perovskites. • p-type CH 3 NH 3 PbI 3 perovskites incorporated with n-type PbSe quantum dots forming bulk heterojunction composites. • Solution-processed room-temperature operated broadband photodetectors. • Responsibility, detectivity and a linear dynamic range of broadband photodetectors.

Strategic combination of metal–organic frameworks and C3N4 for expeditious photocatalytic degradation of dye pollutants

The potential of fabricated silver and bismuth Co-N-doped imidazolate embedded into graphitic nitride BiO-Ag(0)/C3N4@ZIF-67 for the degradation of Methylene blue (MB) and Congo red (CR) dyes have been reported. The synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy photoluminescence (PL) spectroscopy, and electrochemical impedance spectroscopy (EIS). The band gaps of ZIF-67, C3N4and composites were calculated using Tauc plot.Besides,it was revealed that incorporation of silver, bismuth, and C3N4 reduced the band gap energy to 2.2eV. The introduction of metallic species in the precursors promoted better charge separation behavior towards photogenerated electron and hole in the heterojunction composite. Two perilous organic dyes; MB and CR were degraded under natural sunlight irradiation. The photocatalytic efficiency of BiO-Ag(0)/C3N4@ZIF-67 for the removal of CR and MB significantly increased compared to bare ZIF-67. The enhanced photocatalytic activity of BiO-Ag(0)/C3N4@ZIF-67 is attributed to the higher surface area and Plasmon effect of noble silver metal. The solar light-triggered degradation of MB and CR yielded efficient efficiency of 96.5 and 90% for 10mg/L of dye solution each. Additionally, the effect of pH was evaluated for optimizing degradation of CR and MB dyes. The kinetics studies of both CR and MB were clarified according to Langmuir model. The reusability and quenching investigation of active species were carried out to discover find catalytic potential of the composite. Besides, possible dye degradation mechanism was proposed for BiO-Ag(0)/C3N4@ZIF-67. The obtained results indicated that solar-light triggered photocatalyst BiO-Ag(0)/C3N4@ZIF-67 can be employed as a promising approach for photocatalytic elimination of organic pollutants.

Photocatalytic removal of tetracycline by a Z-scheme heterojunction of bismuth oxyiodide/exfoliated g-C3N4: performance, mechanism, and degradation pathway

Antibiotics, once being released into the environment, become recalcitrant organic pollutants, which pose a potential risk to ecological balance and human health. In this study, a Z-scheme heterojunction of bismuth oxyiodide (BiOI)/exfoliated g-C3N4 (BiOI/ECN hereafter) was synthesized by the combination of thermal exfoliation of g-C3N4 and chemical precipitation of BiOI for efficient photocatalytic degradation of tetracycline in aqueous solutions under visible light irradiation. The optimized BiOI/ECN delivered an outstanding degradation rate at circa 0.0705 min−1, which was 10 times higher than that of the bulk g-C3N4. The photocatalytic degradation efficiency of tetracycline remained almost unchanged in a pH range of 3–11, and the BiOI/ECN displayed an excellent photostability upon recycled usage. The photocatalytic mechanism of tetracycline was ascribed to the main reactive oxidation species of photogenerated holes and superoxide radicals. In addition, the possible degradation pathways of tetracycline were investigated by HPLC-MS to identify intermediates. The toxicity of photocatalytic-generated intermediates of tetracycline was found significantly alleviated according to the calculation of quantitative structure–activity relationship prediction. This work not only provides an attractive photocatalyst for the removal of tetracycline but also opens a new avenue for rational design of Z-scheme heterojunction composites for tetracycline degradation.

A novel nano-sized red phosphorus decorated borocarbonitride heterojunction with enhanced photocatalytic performance for tetracycline degradation

Red phosphorus/borocarbonitride heterojunction composites were prepared by a vaporization–deposition method for excellent photocatalytic activity towards tetracycline degradation.

TiO2–ZnO/Au ternary heterojunction nanocomposite: Excellent antibacterial property and visible-light photocatalytic hydrogen production efficiency

TiO 2 –ZnO/Au ternary heterojunction nanocomposite was fabricated by producing TiO 2 nanosheets first using solvent-thermal method followed by Au deposition and ZnO deposition respectively. The TiO 2 nanosheets provide a relatively large surface area for the good dispersion of ZnO nanoparticles and Au particles and sufficient contact with the medium, which contribute to the excellent photocatalytic performances of TiO 2 –ZnO/Au heterojunction composite. The phases and structures, morphologies, surface and optical properties of the ternary heterojunction composite are well-characterized. Subsequently, the photocatalytic hydrogen generation of TiO 2 –ZnO/Au is evaluated under visible light irradiation. TiO 2 –ZnO/Au ternary heterojunction composite has efficient light absorption ability and excellent performances in photocatalytic hydrogen generation (1068 μmol/g under the irradiation of visible light for 4 h) and antibacterial properties (reaching 98.2%). TiO 2 –ZnO/Au ternary heterojunction nanocomposite has a large potential to be used in areas such as interior wall coating.

The doping of B in ZnO/CdS for enhanced visible-light H2 production

A B-ZnO/CdS heterojunction composite was prepared and its H2 production activity was enhanced up to 13 100 μmol h−1 g−1.

Enhanced photocatalytic activity of brown H4Nb6O17/g-C3N4 composite for visible-light driven H2O2 production

Novel, brown H4Nb6O17, was synthesised and a composite heterojunction with g-C3N4 was formed, showing enhanced photocatalytic activity for H2O2 production.

Distinct role of hexagonal tungsten in tungsten/ceria heterojunction in efficient utilization of visible flux

Mixed phase metal oxide photocatalysts at optimised phase ratio are known to perform better than their monophasic counterpart in visible spectrum. In tungsten oxide (WO3) too high visible activity is seen in multi-phasic systemhaving dominant hexagonal phase and is attributable to its superior photon harvesting characteristicsthan other phases. In a hetero-composite with ceria due to suitable band edge position further enhancement in the photoactivity is seen mainly with its monoclinic(m-WO3) phase. In this work, h-WO3/Ce3+/Ce4+based hetero-composites have been realized with different molar ratio of W/Ce.While h-WO3 dominates all the systems,m-WO3appears in the system at low concentration of Ce and disappears at higher concentrations. The resultant sharp increase (13.66X) in the visible photocatalytic performance of mixed phase-WO3/ceria composite compared to pristine h-WO3 shows a further jump (44X) in the monophasic-WO3/ceria composite with the highest concentration of ceria synthesized. The characterization by X-ray diffraction (XRD), UV-VIS spectroscopy (UV-VIS DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, transmission electronmicroscopy(TEM), and scanning electron microscopy(SEM) with energy dispersive x-ray analysis (EDX) reveal the complex role distinct phase junctions of homo-/hetero-composites. The mixed-phase h-WO3/m-WO3homojunction, h-WO3/Ce3+ composite heterojunction and h-WO3/Ce3+/Ce2+ with both hetero-composite (h-WO3/Ce3+ and h-WO3/Ce2+) and homo-composite(Ce3+/Ce4+) heterojunction in the samples has been identified, and their roles have been analyzed to correlate with their respective visible light photoactivity.

Direct Z-Scheme Nanoporous Bivo4/Cds Quantum Dots Heterojunction Composites as Photoanodes for Photocathodic Protection of 316 Stainless Steel Under Visible Light

Direct Z-Scheme Nanoporous Bivo4/Cds Quantum Dots Heterojunction Composites as Photoanodes for Photocathodic Protection of 316 Stainless Steel Under Visible Light

Rational Design of Dynamic Z-Scheme Heterojunction Composites for Photocatalytic Cr(Vi) Reduction and H2 Production: An Experimental and Computational Study

Rational Design of Dynamic Z-Scheme Heterojunction Composites for Photocatalytic Cr(Vi) Reduction and H2 Production: An Experimental and Computational Study

Preparation of p-LaFeO₃/n-Fe₂O₃ Heterojunction Composites by One-Step Hydrothermal Method and Gas Sensing Properties for Acetone

Perovskite LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> materials have received increasing attention in volatile organic compound (VOC) gas detection due to their unique crystal structure and excellent physicochemical properties. However, achieving high sensitivity with a low limit of detection at low temperature is still an important research topic. In this work, p-LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /n-Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> composites were prepared by a simple one-step hydrothermal method for the detection of acetone gas. Various characterizations showed that the LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> composites were successfully synthesized. The test results showed that the LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> composites have more excellent gas sensing properties than acetone compared with pure LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> material. The response of the LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor to 10 ppm acetone (23.5) at 210 °C is almost five times larger than that of the pure LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> material. In addition, the LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor has a low limit of detection (100 ppb), good long-term stability, and selectivity. The enhanced acetone sensing performance can be ascribed to changes in the electronic structure and surface properties caused by heterojunctions, as well as to the synergistic effect formed between the two components. This work provides a simple synthetic strategy to enhance the acetone gas sensing performance of perovskite-type LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , which has promising applications in industrial production and healthcare.

The photocatalytic properties and construction of a WS2/MoS2/CdS heterojunction

The as-prepared WS2/MoS2/CdS composite heterojunction semiconductor exhibited high photocatalytic activity when degrading organic pollutants under visible light illumination.

Magneto-tunability of photocurrent in Zn0.3Ni0.7Fe2O4/ZnO-rGO composite heterojunction device

We studied light and magnetic field dependent DC transport properties of Zn0.3Ni0.7Fe2O4/ZnO-reduced graphene oxide composite heterojunction. Current through the heterojunction is expected from the carrier injection and tunneling in forward and reverse bias, respectively. Application of magnetic field has shown both negative magnetoresistance (MR) at forward bias and positive MR at reverse bias. The negative MR is attributed to the reduction of spin dependent scattering in the bulk of Zn0.3Ni0.7Fe2O4 layer. On the other hand, under reverse bias, a magnetic field dependent increase of depletion region in Zn0.3Ni0.7Fe2O4 side is supposed to take place, resulting in a positive MR. Under 660 nm visible light illumination, photoresponse has been observed. Under illumination, negative MR is found in reverse bias. This negative MR is expected to be associated with the magnetic field dependent widening of reverse bias depletion region. In forward bias voltages, under strong illumination of 3.08 mW/cm2 of 660 nm light, a positive MR is found. This positive MR is associated with the light dependent enhancement of depletion width at Zn0.3Ni0.7Fe2O4 side under high injection mode. When the applied voltage is swept along a cycle, irreversible nature of I-V characteristics is observed.

Sn-doped BiOI assisted the excellent photocatalytic performance of multi-shelled ZnO microspheres under simulated sunlight

To deal with the environmental pollution and energy crises, it is indispensable to find green and efficient means to overcome these challenges. Herein, the Sn-doped BiOI modified multi-shelled ZnO heterojunction composite with a high performance are designed and prepared. The results prove the formation of heterojunction structure in the composites and the morphology is shown as the multi-shelled microsphere. The performances of the composites are evaluated by different kinds of antibiotic degradation and H2-evolution under simulation sunlight irradiation. The measurements present that the Sn-BiOI/ZnO (SBZs) could completely remove ciprofloxacin (CIP) within 100 min, which is 4.18 times that of ZnO in kinetics. Typically, the degradation rate of CIP for SBZ6 is over 99.9%, which is more than 25% higher than that of pure ZnO microspheres. In addition, the rate of H2 production could reach 3.08 mmol g−1∙ h−1, which is 1.79 times of the pure ZnO microspheres. The boosted performance of the composites may originate from the enhanced electronic transmission efficiency and improved separation and recombination efficiency of electrons/holes. The charge transfer mode in the SBZs heterojunction composites is proposed and verified as the Z-scheme by the active species experimental and the possible electron transfer path analysis. Therefore, Sn-doped BiOI is introduced into multi-shelled ZnO microsphere to form contact heterojunction interfacial, which greatly improves the photocatalytic performances of the SBZs. Furthermore, this work supplies a strategy for designing and preparing highly active ZnO-based heterojunction composites, which could effectively address the challenges of environmental remediation and clean energy production.

Activation of Persulfate for Improved Naproxen Degradation Using FeCo2O4@g-C3N4 Heterojunction Photocatalysts.

An effective heterojunction with robust charge separation and enormous degradation efficiency is the major task for photocatalyst preparation. In this study, we have prepared the FeCo2O4-loaded g-C3N4 nanosheet by the sol–gel-assisted calcination method for photo-Fenton-like degradation under visible-light irradiation by activating persulfate. The nanocomposite exhibits a higher charge separation efficiency than pure g-C3N4 and FeCo2O4 for the degradation reaction against naproxen drugs. An effective interaction between the nanoparticles increases the degradation efficiency up to 91% with a synergistic index of 73.62%. Moreover, the nanocomposite exhibits a 78% mineralization efficiency against the naproxen pollutant under visible-light irradiation. For practical implementation, the degradation reaction was tested with various pH values, different water sources (DI, lake, and tap water), and light sources (LED (visible)/direct sunlight (UV–visible)). Moreover, the possible degradation mechanism predicted by the elemental trapping experiment and the recycling experiment clearly revealed that the heterojunction composite has a high enough degradation stability.

Ultrasensitive electrochemical detection of furazolidone in biological samples using 1D-2D BiVO4@MoS2 hierarchical nano-heterojunction composites armed electrodes

In this work, the hydrothermally synthesized of BiVO4@MoS2 hierarchical nano-heterojunction composite is employed as a novel electrocatalyst for electrochemical sensing of Furazolidone (FZE) drug by modifying the glassy carbon electrodes (GCE). The Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy are used to thoroughly investigate the functional groups, vibrational modes, crystal structure, elemental composition and surface topography of the heterojunction composite. The physical characterization results revealed the successful construction of 1D-2D BiVO4@MoS2 hierarchical nano-heterojunction composite. When these unique architectures are reinforced on GCE surface, we achieved an enhanced electroactive surface area of 0.154 cm2. The electrochemical performance of 1D-2D BiVO4@MoS2 is examined though cyclic voltammetry and differential pulse voltammetry (DPV) analysis. The BiVO4@MoS2 composites exhibited an excellent electrocatalytic activity in sensing of FZE with superior linear detection ranges of 0.01–14 and 14–614 μM. The limit of detection (LOD) of the BiVO4@MoS2 based sensor is determined to be 2.9 nM which is far superior than other reported FZE sensors. Consequently, it is evident from the investigation that the BiVO4@MoS2 based FZE sensor can be recommended for analyzing real time samples like human urine and blood serum with appreciable recovery.

S-scheme g-C3N4/TiO2/CFs heterojunction composites with multi-dimensional through-holes and enhanced visible-light photocatalytic activity

A novel multi-dimensional through-holes structure of g-C3N4 with adjustable pore size was prepared by controlling the mass ratio of oxamide (OA, structure guiding agent) to urea during one-step calcination process, and a break-rearrangement mechanism was explored. Then, a series of porous g-C3N4/TiO2 (CT) composites with uniformly deposited TiO2 nanoparticles were prepared based on the multi-dimensional framework by a facile hydrothermal method. The results show that a new S-scheme heterojunction with multi-dimensional through-channel structure was obtained, which is particularly desired for enhancing the visible-light utilization, reducing the carrier recombination rate and enhancing redox capacity. The CT composite obtained at hydrothermal treatment time of 2 h has a specific surface area of 180.15 m2 g-1, which shows high degradation capability (99.99%) for tetracycline hydrochloride (TC·HCl) under 350 W Xe lamp irradiation for 90 min. In addition, CT nanostructures was in-situ growth on carbon fiber (CFs), the degradation rate constant is 0.1566 min-1, and 90% of the degradation efficiency can be maintained even after 5 consecutive cycles. It is expected to provide an effective reference for solving the problems of recovery difficulty and low reuse rate of powder photocatalytic materials.

Bi2O2CO3/red phosphorus S-scheme heterojunction for H2 evolution and Cr(VI) reduction

Red phosphorus (RP) has a suitable energy band structure and excellent photocatalytic properties. However, there are some problems, such as low quantum efficiency and serious photogenerated electron-hole recombination. The S-scheme heterostructure shows great potential in facilitating the separation and transfer of photogenerated carriers and obtaining strong photo-redox ability. Herein, hydrothermally treated red phosphorus (HRP) was combined with Bi2O2CO3 to construct Bi2O2CO3/HRP S-scheme heterojunction composite. The Bi2O2CO3 content was optimized, and the 5 %Bi2O2CO3/HRP composite obtained at 5 %Bi2O2CO3 mass fraction exhibited the strongest photoreduction ability. The Cr(VI) photoreduction and photolytic hydrogen production rates were as high as 0.22 min−1 and 157.2 μmol •h−1, which were 7.3 and 3.0 times higher than those of HRP, respectively. The promoted photocatalytic activity could be attributed to the formation of S-scheme heterojunctions, which accelerated the separation and transfer of useful photogenerated electron-hole pairs, while enhancing the recombination of relatively useless photogenerated electron-hole pairs, thereby resulting in the highest photocurrent density (17.3 μA/cm2) of the 5 %Bi2O2CO3/HRP composite, which was 1.6 and 4.3 times higher than pure Bi2O2CO3 (10.5 μA/cm2) and pure HRP (4.0 μA/cm2), respectively. This work would provide an advanced approach to enhance the photocatalytic activity of RP.

Corrigendum: Novel BaSnO3/TiO2@HNTs Heterojunction Composites with Highly Enhanced Photocatalytic Activity and Stability

The authors declare no conflict of interest.

Construction of Au/g-C3N4/ZnIn2S4 plasma photocatalyst heterojunction composite with 3D hierarchical microarchitecture for visible-light-driven hydrogen production

In this paper, a novel Au/g-C3N4/ZnIn2S4 plasma photocatalyst heterojunction composite with 3D hierarchical microarchitecture has been successfully constructed by integrating Au/g-C3N4 plasmonic photocatalyst composite with 3D ZnIn2S4 nanosheet through a simple hydrothermal process. The Au nanoparticles were firstly anchored on the surface of pristine g-C3N4 material to get Au/g-C3N4 plasmonic photocatalyst. Ascribing to the surface plasmon resonance of Au nanoparticles, the obtained Au/g-C3N4 plasmonic photocatalyst shows a significant improved photocatalytic activity toward hydrogen production from water with visible light response comparing with pristine g-C3N4. Further combining Au/g-C3N4 plasmonic photocatalyst with 3D ZnIn2S4 nanosheet to construct a heterojunction composite. Owing to the synergistic effect of the surface plasmon resonance of Au nanoparticles in Au/g-C3N4 and the heterojunction structure in the interface of Au/g-C3N4 and ZnIn2S4, the prepared Au/g-C3N4/ZnIn2S4 plasma photocatalyst heterojunction composite shows an excellent photocatalytic activity toward hydrogen production from water with visible light response, which is around 7.0 and 6.3 times higher than that of the pristine C3N4 and Znln2S4 nanosheet, respectively. The present work might provide some insights for exploring other efficient heterojunction photocatalysts with excellent properties.