Core–shell structure of metal loaded CdS–SiO2 hybrid nanocomposites for complete photomineralization of methyl orange by visible light

• Creation of void in CdS/SiO2 nanorod core–shell structure by Ar ion laser etching.
• Core size was reduced from 6 to 2.4 nm as a function of wavelength of light used.
• Metal loading improved the photodegradation efficiency to ∼91% under visible light.
• Metals follow the order – Pt > Au > Rh > Pd > Ag ∼ Cu due to their different nature.
• Plausible degradation pathway was proposed for mineralization of methyl orange.

Core–shell morphology of silica (SiO2) shell coated CdS nanorod core (SNR) of aspect ratio = 21 and SiO2 shell thickness (1.4 nm) has been made for better photostability and photochemical activity (∼66%) of CdS nanoparticles. The size of the CdS core was reduced (from 6 to 2.4 nm) as a function of wavelength using 488 nm Ar ion laser irradiation that displayed high fluorescence and improved photocatalytic activity (∼72%) due to more surface active atoms. Different transition metal particles in the size range of 2–5 nm have been deposited to form a metal–semiconductor junction that shows improved photodegradation of methyl orange (∼91%) in 45 min under visible light (250 W, tungsten–halogen lamp) in an order – Pt > Au > Rh > Pd > Ag ∼ Cu as a function of their nature, particle size distribution, redox potential, Fermi level equilibration, effective number of interfacial contacts, etc. Different parameters such as surface area, pH, light intensity, catalyst and dye concentration also play a significant role. Complete mineralization was studied by identifying different intermediates via GC–MS study and measuring CO2 (40 μmol). A plausible mechanistic degradation pathway was proposed for the complete mineralization.

Figure optionsDownload high-quality image (224 K)Download as PowerPoint slide