Photocatalytic Degradation of Rhodamine B and Malachite Green by Cobalt Sulfide Nanoparticles

Abstract

Present study reports the simple and cost effective thermolytic method for the synthesis of cobalt sulphide nanoparticles (CoS NPs). The PXRD spectrum of cobalt sulphide (CdS) nanoparticles exhibited four peaks indexed to (100), (101), (102) and (110) crystal planes. The average particle size observed from DLS and PXRD was in the range 4.81-12.20 nm. A blue shift in band gap was observed from UV-visible spectra. The FESEM and TEM studies revealed that cobalt sulfide nanoparticles are of cubic and rectangle shapes. FTIR spectra of hexadecylamine (HDA) capped CoS NPs exhibited ν(N-H) absorption around 3350-3240 cm–1. The stretching frequency due to ν(Co-S) appeared in the region 334-332 cm–1. Proton NMR (1H) spectra of CoS NPs showed signals at nearly same positions as in case of capping agent, suggesting its capping nature. ESI-MS analyses of cobalt sulphide nanoparticles displayed peak at m/z = 124.93 corresponding to the [CoS2]+ ion. Thermogravimetric curves showed single step decomposition corresponding to 84.28% weight loss and 15.72% as final residue due to cobalt oxide. The degradation rate of rhodamine B and malachite green dyes after irradiating with sunlight showed 92-94% degradation while irradiated with UV-light of 4.8 eV show much slower degradation rate.

Catalytic reduction of 4‐nitrophenol using synthesized and characterized CoS@MorphcdtH/CoS@4‐MPipzcdtH nanoparticles

“…The proposed fragmentation mechanism (Figures 7 and 8) is in agreement with the ring‐opening mechanism of cyclic amines which involves the cleavage of the bond next to the nitrogen atom. [ 25 ]…”

“…Thus the observed PXRD patterns (Figures 11 and 12) of TG residues confirmed the CoO as final decomposition product and hence is in agreement with the proposed decomposition pathway. [ 25 ]…”

“…Based on the steric interactions of these groups, the trend well matched with the size of nanoparticles as evident from TEM studies. UV-visible absorption of CoS@MorphcdtH NPs and CoS@4-MPipzcdtH NPs exhibited broad peaks which were blue-shifted as compared with bulk CoS. [25,29,30] Slight variation in broadness and positions of peaks from bulk to CoS@MorphcdtH NPs and CoS@4-MPipzcdtH NPs (Figure 6) may be because of the absorptions of capping agents. The band gaps in the present study were found to be 3.86 eV and 3.65 eV for CoS@MorphcdtH NPs and CoS@4-MPipzcdtH NPs, respectively.…”

“…Thermal analysis of samples was carried and details about it were found elsewhere. [25] turns into a faded yellow-green color. The catalytic behavior was analyzed at a concentration of 0.004 g of CoS@MorphcdtH NPs and 0.005 g of CoS@4-MPipzcdtH NPs per 1 mL of 10 À4 M aqueous solution.…”

“…SU8010 was used to determine the morphology and elemental composition of both samples and details about the instruments and method were found elsewhere. [ 25 ] The crystalline nature of CoS NPs was analyzed using a powder x‐ray diffraction (PXRD) method on a XPERT–PRO x‐ray diffractometer operating at the voltage of 45 kV, the current of 40 mA with CuK α radiation at the wavelength of1.5406nm and step size of 0.050 per sec counting in the range 2 θ from 10° to 80°. The range of the UV–visible spectrophotometer was 900–200 nm, methanol was used as a reference and the surface spectrum of CoS NPs was measured.…”