Zn0.2Cd0.8S alloyed films were prepared on glass substrates at room temperature using chemical bath deposition method. The obtained films were annealed at temperatures ranging from 200°C to 500°C with heating rate of 5°C/min and annealed at 400°C with heating rate of 2°C/min and 10°C/min. The films were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and UV-VIS spectrophotometer. The increasing of annealing temperature increases the crystallinity and the mean grain size of Zn0.2Cd0.8S alloyed films and significantly enhances the absorption in the visible region. The efficient visible light photocatalytic activity for annealed Zn0.2Cd0.8S alloyed films is associated with the larger size grain and the higher crystallinity.
Semiconductor assisted photocatalysis has received increasing attention owing to its potential in simultaneously solving the energy shortage and environmental problems [
Heat treatment is often used to tune the structure and properties of materials. By using appropriate parameters for heat treatment, different shapes [
All the chemicals are analytical reagents and used without further purification. The glass slides were cleaned with acetone, alcohol, and deionized water, respectively. 0.005 M ZnSO4
The structure was characterized by X-ray diffraction (XRD, D8). The morphologies of the products were characterized by scanning electron microscopy (SEM, Hitachi S-4800) and the components were measured by energy-dispersive spectroscopy (EDS). The fluorescence (FL) spectra were obtained by fluorescence spectrophotometer (F-2500) with an excitation wavelength of 380 nm laser line. The absorption spectra of the films were determined using a double beam UV-VIS spectrophotometer (TU-1901) in the wavelength range of 300–800 nm.
The photocatalytic activity of Zn0.2Cd0.8S films was evaluated by photodegradation of aqueous solution of methyl orange under the irradiation of 55 W LED lamps. The catalytic experiments were carried out with 60 ML methyl orange solution and annealed Zn0.2Cd0.8S films. The suspension was magnetically stirred and placed at 3 cm from the lamp. During irradiation, the samples were withdrawn at regular time intervals and centrifuged to remove the catalysts. The absorption spectra of the solution were determined using UV-VIS spectrophotometer.
SEM images of Zn0.2Cd0.8S alloyed films at different annealing conditions are delineated in Figure
SEM micrographs of Zn0.2Cd0.8S alloyed films at different annealing conditions are as follows: (a) 200°C and 5°C/min, (b) 300°C and 5°C/min, (c) 400°C and 5°C/min, (d) 500°C and 5°C/min, (c1) 400°C and 2°C/min, and (c2) 400°C and 10°C/min.
Zn0.2Cd0.8S alloyed films were characterized by XRD to obtain information about the structure of the products. Figure
XRD patterns of Zn0.2Cd0.8S alloyed films (a) annealed at 200°C, 300°C, 400°C, and 500°C, respectively, with heating rate of 5°C/min. (b) Annealed at 400°C with heating rate of 2°C/min, 5°C/min, and 10°C/min, respectively.
The optical absorption spectra of Zn0.2Cd0.8S alloyed films annealed at different temperatures with different heating rates are illustrated in Figure
Optical absorption spectra of Zn0.2Cd0.8S alloyed films (a) annealed at 200°C, 300°C, 400°C, and 500°C, respectively, with heating rate of 5°C/min. (b) Annealed at 400°C with heating rate of 2°C/min, 5°C/min and, 10°C/min, respectively.
The degradation efficiency is shown in Figure
Photocatalytic degradations of methyl orange in the presence of Zn0.2Cd0.8S alloyed films under visible light irradiation. (a) Annealed at 200°C, 300°C, 400°C, and 500°C, respectively. The inset figure is a typical absorption spectral change. (b) Annealed at 400°C with heating rate of 2°C/min, 5°C/min, and 10°C/min, respectively.
It is known that the photoactivity of semiconductors is particle size-dependent [
Zn0.2Cd0.8S alloyed films prepared by simple chemical bath deposition method were studied as photocatalysts for degradation of methyl orange under visible light irradiation. The grain size increases and crystallinity is enhanced for the Zn0.2Cd0.8S alloyed films with increasing annealing temperature and heating rate. Moreover the absorption edge obviously shifts to longer wavelength with increasing the annealing temperature and the heating rate. Increasing the annealing temperature and the heating rate can enhance photocatalytic activities of Zn0.2Cd0.8S alloyed films under visible light irradiation. This work provides a simple and efficient method to enhance the photocatalytic activity of semiconductors.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by the National Natural Science Foundation of China (Grant nos. 11074069, 61176116), the Hunan Provincial Natural Science Foundation of China (Grant no. 12JJ3009), and Aid program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province.