Changchang Ma

Transfer Charge and Energy of Ag@CdSe QDs-rGO Core–Shell Plasmonic Photocatalyst for Enhanced Visible Light Photocatalytic Activity

Plasmonic heteronanostructures in semiconductor type display extraordinary photocatalytic efficiency induced by the plasmonic energy that operates in the Ag@CdSe-rGO hybrid ternary composites. The obtained plasmonic photocatalysts in nanoscale were fabricated by using a one-step hydrothermal method, during which the in situ nucleation of Ag@CdSe core-shell nanoparticles and the reduction of GO to rGO occurred simultaneously. Three different roles of Ag core and the junction of synergistic properties arising from the introduced rGO jointly enhanced the optical properties of CdSe. Localized plasmon resonance (LPR) effects of plasmonic Ag contribute to the separation of photogenerated e(-)/h(+) pairs via the electrons and resonant energy transfer. Electrochemical investigations have further confirmed the enhanced separation of the photogenerated e(-)/h(+) pairs. From comparative photocatalytic experiments of Ag@CdSe-rGO and Ag/CdSe-rGO, the plasmonic effect of the Ag core in the Ag@CdSe-rGO nanostructure serves to prolong the charge separation under visible light beyond common attached trimers.

Enhanced photocatalytic degradation of tetracycline antibiotics by reduced graphene oxide–CdS/ZnS heterostructure photocatalysts

In this work, reduced graphene oxide (RGO)–CdS/ZnS heterostructure composites have been successfully synthesized by a hydrothermal method by assembling the CdS/ZnS heterostructure nanoparticles on RGO sheets and the reduction of GO occurs simultaneously. The as-prepared RGO–CdS/ZnS composites with the content of 15% RGO exhibit highly active photodegradation of TC. A possible mechanism for the enhanced photocatalytic activity has been discussed. The CdS/ZnS heterostructure facilitates the transformation of electrons, which is excited by light irradiation in the conduction band of CdS. RGO is supposed to be an electron transfer channel, which is used to reduce the recombination of electron–hole pairs, thus enhancing the photo-conversion efficiency. By profiting from the synergy of RGO and CdS/ZnS heterostructure, the photocatalysts not only show a better photocatalytic activity in tetracycline antibiotics but also prevent pure CdS or ZnS from photocorrosion. At last, RGO–CdS/ZnS shows remarkable stability and cyclic performances.

Hydrothermal synthesis and enhanced visible-light photocatalytic activity of octahedral Bi2WO6 modified with CdSe quantum dots

In this paper, octahedral Bi2WO6 modified with CdSe quantum dots was synthesized by a hydrothermal method. This as-prepared CdSe–Bi2WO6 photocatalyst exhibited a higher photocatalytic activity for the degradation of tetracycline (TC) than octahedral Bi2WO6. Moreover, 15%-CdSe–85%-Bi2WO6 showed the best Dr of 65.38%, which is over 5 times that of the pure Bi2WO6. Furthermore, the as-synthesized CdSe–Bi2WO6 composite photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis) and photoluminescence spectroscopy (PL).

One-step hydrothermal synthesis of cobalt and potassium codoped CdSe quantum dots with high visible light photocatalytic activity

The effect of metal ion doping on the electronic structure and optical properties of CdSe quantum dots has been investigated by various characterization techniques and experiments. Various cation codoped CdSe quantum dot photocatalysts were synthesized via a hydrothermal method. The prepared quantum dots were examined using X-ray diffraction, fluorescence spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The activities of the photocatalysts were evaluated with respect to the photodegradation of tetracycline hydrochloride solutions under simulated sunlight irradiation. 3%Co–4%K/CdSe quantum dots showed a higher photocatalytic activity than others within 30 min of visible light irradiation. Furthermore, there was hardly any decrease in the catalytic efficiency after the fourth experimental cycle. Identification data illustrate that Co and K codoping may cause improvement in the photocatalytic performance of CdSe quantum dots, which is crucial for tetracycline hydrochloride degradation under simulated sunlight irradiation. Therefore, this study demonstrates a promising strategy for the design of highly efficient photocatalysts for the remediation of aqueous pollutants.

Construction of vesicle CdSe nano-semiconductors photocatalysts with improved photocatalytic activity: Enhanced photo induced carriers separation efficiency and mechanism insight

Visible-light-driven photocatalysis as a green technology has attracted a lot of attention due to its potential applications in environmental remediation. Vesicle CdSe nano-semiconductor photocatalyst are successfully prepared by a gas template method and characterized by a variety of methods. The vesicle CdSe nano-semiconductors display enhanced photocatalytic performance for the degradation of tetracycline hydrochloride, the photodegradation rate of 78.824% was achieved by vesicle CdSe, which exhibited an increase of 31.779% compared to granular CdSe. Such an exceptional photocatalytic capability can be attributed to the unique structure of the vesicle CdSe nano-semiconductor with enhanced light absorption ability and excellent carrier transport capability. Meanwhile, the large surface area of the vesicle CdSe nano-semiconductor can increase the contact probability between catalyst and target and provide more surface-active centers. The photocatalytic mechanisms are analyzed by active species quenching. It indicates that h+ and O2- are the main active species which play a major role in catalyzing environmental toxic pollutants. Simultaneously, the vesicle CdSe nano-semiconductor had high efficiency and stability.

Enhanced photocatalytic performance and stability of visible-light-driven Z-scheme CdS/Ag/g-C3N4 nanosheets photocatalyst

A novel Z-scheme CdS/Ag/g-C3N4 nanosheets photocatalyst was synthesized by combining the hydrothermal and photo-deposition techniques, where Ag nanoparticles as carrier transport channels significantly improve the separation efficiency of electron–hole pairs. Outstanding photocatalytic activity was observed, which indicates that the constructed Z-scheme can retain the oxidizing ability of the CdS valence band and reducing ability of the g-C3N4 conduction band. In addition, trapping experiments and ESR measurement reveal that the superoxide radical (˙O2−) and holes (h+) are the predominant active species. This study provides a new approach to perfect the Z-scheme photocatalytic system for application in the efficient treatment of persistent pollutants in wastewater.

Solvothermal-Assisted Synthesis of Biomass Carbon Quantum Dots/Bismuth Oxyiodide Microflower for Enhanced Photocatalytic Activity

In this paper, the biomass carbon quantum dots (CQDs) modified flower-like BiOI (CQDs/BiOI) composite photocatalyst was synthesized by a facile solvothermal method. Compared with the pristine BiOI,...

Synthesis of Fe3O4/C with Cauliflower-Like BiVO4 for Improved Separation Efficiency of Charge Carriers and Photocatalytic Activity

Fe3O4/C/BiVO4 composite photocatalyst was fabricated successfully by a simple approach using yeast as a carbon source. Fe3O4/C/BiVO4 sample exhibited higher efficiency for photocatalytic degradation of tetracycline (TC) as compared to pure BiVO4 under visible light. In addition, after five recycles of photodegradation of TC, Fe3O4/C/BiVO4 showed a slight loss in photocatalytic activity, which confirmed its stability and long-time reusability. The photocatalytic mechanism was studied by active species trapping experiments, which revealed that the holes (h+) and superoxide radical (˙O-2) played a key role in TC degradation. Moreover, photocatalyst could be easily recycled by an external magnetic field and reused without any loss in photocatalytic activity. This work provides a simple, eco-friendly and exemplary strategy for improving photodegradation activity of BiVO4-based photocatalyst.

HYDROTHERMAL SYNTHESIS AND ENHANCED VISIBLE-LIGHT PHOTOCATALYTIC ACTIVITY OF CdS QUANTUM DOTS SENSITIZED CARBON NANOTUBES (CNTs) NANOCOMPOSITE

A new-type photocatalyst of cadmium sulfide carbon nanotubes (CdS/CNTs) was prepared by the hydrothermal method. This as-prepared CdS/CNTs composite photocatalyst was proved to exhibit an excellent photocatalytic activity for degradation of tetracycline (TC). Specially, the 95%-CdS–5%-CNTs composite photocatalyst played the best degradation rate (81.2%) in 60 min under the visible light irradiation. Moreover, this 95%-CdS–5%-CNTs composite photocatalyst possessed great stability and could be used at least four cycles with almost no loss of photocatalytic efficiency. Furthermore, the as-synthesized CdS/CNTs composite photocatalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffused reflectance spectra (UV-Vis), Raman and thermal gravimetry (TG). In addition, the possible mechanism and kinetics of photodegradation of TC with CdS/CNTs photocatalyst was also discussed.

A two step hydrothermal process to prepare carbon spheres from bamboo for construction of core–shell non-metallic photocatalysts

This work reports the direct transformation of the biomass of bamboo into carbon spheres by two step hydrothermal carbonization (HTC) at 180–200 °C. Such carbon spheres have potential applications as electrode materials with excellent electrical conductivity and high chemical stability. The biochar spheres (BS) were modified via protonation of g-C3N4 to form non-metallic photocatalysts with a unique core–shell architecture. In the BS@g-C3N4 core–shell photocatalysts, the protonated g-C3N4 sheets were the main photocatalyst and the biochar spheres acted both as a reservoir and a sensitizer, and displayed outstanding light absorption in nearly the entire wavelength range, due to the narrower gap of the sp2 carbon cluster and large amounts of carbon clusters. Conversion of raw biomass into stable carbon materials under relatively mild conditions offers a promising route to overcoming the challenges in obtaining biochar materials with precisely controlled morphology. Building a green non-metallic photocatalyst is an environmentally friendly embodiment of this.