High-sensitivity hybrid PbSe/ITZO thin film-based phototransistor detecting from 2100 nm to 2500 nm near-infrared illumination

We report that high absorption PbSe colloidal quantum dots (QDs) having a peak absorbance beyond 2100 nm were synthesized and incorporated into InSnZnO (ITZO) channel layer-based thin film transistors (TFTs). It was intended that PbSe QDs with proportionally less photocurrent modulation can be remedied by semiconducting and low off-current ITZO-based TFT configuration. Multiple deposition scheme of PbSe QDs on ITZO metal oxide thin film gave rise to nearly linear increase of film thickness with acceptably uniform and smooth surface (less than 10 nm). Hybrid PbSe/ITZO thin film-based phototransistor exhibited the best performance of near infrared (NIR) detection in terms of response time, sensitivity and detectivity as high as 0.38 s, 3.91 and 4.55 × 107 Jones at room temperature, respectively. This is indebted mainly from the effective diffusion of photogenerated carrier from the PbSe surface to ITZO channel layer as well as from the conduction band alignment between them. Therefore, we believe that our hybrid PbSe/ITZO material platform can be widely used to be in favour of incorporation of solution-processed colloidal light absorbing material into the high-performance metal oxide thin film transistor configuration.

Gas-Phase Fluorination of g-C3N4 for Enhanced Photocatalytic Hydrogen Evolution

Graphitic carbon nitride (g-C3N4) has attracted much attention because of its potential for application in solar energy conservation. However, the photocatalytic activity of g-C3N4 is limited by the rapidly photogenerated carrier recombination and insufficient solar adsorption. Herein, fluorinated g-C3N4 (F-g-CN) nanosheets are synthesized through the reaction with F2/N2 mixed gas directly. The structural characterizations and theoretical calculations reveal that fluorination introduces N vacancy defects, structural distortion and covalent C-F bonds in the interstitial space simultaneously, which lead to mesopore formation, vacancy generation and electronic structure modification. Therefore, the photocatalytic activity of F-g-CN for H2 evolution under visible irradiation is 11.6 times higher than that of pristine g-C3N4 because of the enlarged specific area, enhanced light harvesting and accelerated photogenerated charge separation after fluorination. These results show that direct treatment with F2 gas is a feasible and promising strategy for modulating the texture and configuration of g-C3N4-based semiconductors to drastically enhance the photocatalytic H2 evolution process.

Semiconductor Quantum Dots (CdX, X = S, Te, Se) Modify Titanium Dioxide Nanoparticles for Photodynamic Inactivation of Leukemia HL60 Cancer Cells

Titanium dioxide nanoparticles (TiO2-NPs) are highly efficient photosensitizers in traditional photodynamic therapy (PDT). The particle size of TiO2-NPs is small, only about 20 nm. However, the demands of ultraviolet light (UV) excitation feature shallow tissue penetration depth and may lead to severe tissue photon damage. Thus, in this research, TiO2-NPs are modified with semiconductor quantum dots (QDs) CdX (X = S, Te, Se) in various methods, such as ultrasonic, hydrothermal, sol-gel, aqueous phase, and hydrolysis precipitation. The transmission electron microscopy (TEM) images show that the size of CdSe-TiO2 is ranging from 6 to 14 nm. The ultraviolet-visible (UV-Vis) spectrum demonstrates that the CdX (X = S, Te, Se) modification can successfully extend the absorption range of TiO2-NPs into a different visible light region. CdSe QDs have the narrowest band gap compared with CdX (X = S, Te, Se) QDs. Visible light-activated CdSe-TiO2 nanocomposite shows the highest PDT inactivation efficiency toward HL60 cells compared with CdX-TiO2. The photogenerated carrier separation efficiency of CdSe-TiO2 nanocomposite is the highest shown in a fluorescence spectrum (FS). Furthermore, when conjugated with folic acid (FA), the prepared FA-CdX-TiO2 (X = S, Se) exhibits excellent cancer-targeting ability during PDT treatment. Optimum PDT efficiency of FA-CdSe-TiO2 indicates that photocatalytic and targeting ability is much higher than pure TiO2 and CdSe-TiO2. Our results provided a detailed investigation on the PDT performance of CdX (X = S, Te, Se) modified TiO2 and may act as a guide for further design of highly targeted performance visible-light response TiO2-NPs.

Preparation of Novel ZnO/Cu2O Heterojunctions Composite Film by Codeposition Method and Their Enhanced Photocatalytic Performance Analysis

IIn this paper, a codeposition method is used to prepare ZnO/Cu2O composite film with a heterojunction structure in one step. The microstructure and photoelectric properties of the prepared ZnO/Cu2O composite film are characterized and analyzed, and its photocatalytic performance is evaluated. Compared with pure the Cu2O film, the composite film exposes more (111) crystal planes, and has a smaller impedance and a larger photocurrent and open circuit voltage value. These findings indicate that the ZnO/Cu2O composite film exhibits excellent photogenerated carrier separation and migration efficiencies. Among the prepared samples, M2 demonstrates the highest photocatalytic and recycling performance. The calculation of the band position shows that the Fermi level of the composite film exhibits a significant shift compared to that of the pure Cu2O film. The analysis shows that the decrease in the recombination probability of photogenerated carriers caused by the shift of the Fermi level and formation of an internal electric field is the main factor for the significant enhancement in the Cu2O photocatalytic performance. This article provides a novel method and idea to realize the efficient removal of organic dye pollutants in sewage.

Epitaxial growth of CsPbBr3/PbS single-crystal film heterostructures for photodetection

Epitaxial high-crystallization film semiconductor heterostructures has been proved to be an effective method to prepare single-crystal films for different functional devices in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as building blocks for heterostructures. Here, the conformal vapor phase epitaxy of CsPbBr3 on PbS single-crystal films is realized to form the CsPbBr3/PbS heterostructures via a two-step vapor deposition process. The structural characterization reveals that PbS substrates and the epilayer CsPbBr3 have clear relationships: CsPbBr3(110) // PbS(100), CsPbBr3[ ] // PbS[001] and CsPbBr3[001] // PbS[010]. The absorption and photoluminescence (PL) characteristics of CsPbBr3/PbS heterostructures show the broadband light absorption and efficient photogenerated carrier transfer. Photodetectors based on the heterostructures show superior photoresponsivity of 15 A/W, high detectivity of 2.65 × 1011 Jones, fast response speed of 96 ms and obvious rectification behavior. Our study offers a convenient method for establishing the high-quality CsPbBr3/PbS single-crystal film heterostructures and providing an effective way for their application in optoelectronic devices.

Preparation of Non-polluting Tb-Doped Mesoporous Carbon Nitride Photocatalyst and Study on the Efficacy and Mechanism of Degradation of Antibiotics in Water

Given that the biological treatment of antibiotic wastewater can easily induce resistant bacteria, the photocatalytic degradation of antibiotics is considered a better method for treating antibiotic wastewater. Therefore, the ability to remove Tylosin (TYL) and Tetracycline (TC) in aqueous solution using rare earth element Tb-doped g-C3N4 under simulated natural solar radiation was investigated. A series of rare earth Tb3+ doped mesoporous g-C3N4 were successfully prepared by nitric acid treatment and Tb(NO3)3·5H2O samples showed significantly higher degradation efficiency for TYL and TC than pure g-C3N4. Leaching toxicity experiments were carried out on the catalyst using chard seeds and demonstrated negligible toxicity of the leachate from the catalyst. The structure, elemental state, optical properties, morphology and photogenerated carrier separation of the prepared xTCN catalysts were characterized by XRD, XPS, UV-Vis DRS, TEM and PL. The results showed that Tb doping enhanced the photocatalytic activity of the g-C3N4 catalyst by narrowing the band gap while improving the light-trapping ability; The separation and transport rate of photogenerated carriers were significantly increased after Tb doping. Finally, a simple, efficient and non-polluting Tb-doped carbon nitride photocatalyst is successfully developed in this paper.