Interconnected Hollow Cobalt Phosphide Grown on Carbon Nanotubes for Hydrogen Evolution Reaction.

Transition-metal phosphides are deemed as potential alternative to platinum for large-scale and sustainable electrocatalytic hydrogen production from water. In this study, facile preparation of interconnected hollow cobalt monophosphide (CoP) supported on carbon nanotubes is demonstrated and evaluated as a low-cost electrocatalyst for hydrogen evolution reaction. Hexamethylenetetramine is used as a structure-directing agent to guide the formation of interconnected cobalt oxide, which further grows into interconnected hollow CoP. Interconnected and hollow microstructural artifacts impart benign attributes, such as enhanced specific and electrochemically active surface area, low intrinsic charge transfer resistance, high interfacial charge transfer kinetics, and improved mass transport, to the electrocatalyst. As a result, the as-prepared electrode exhibits remarkable electrocatalytic performance, low onset (18 mV) and overpotential (η10 = 73 mV); small Tafel slope (54.6 mV dec-1); and high turnover frequency (0.58 s-1 at η = 73 mV). In addition, the electrode shows excellent electrochemical stability.

Nanocatalyst support of laser-induced photocatalytic degradation of MTBE.

This study was undertaken to develop a methodology suitable for the direct removal and degradation of methyl tertiary butyl ether (MTBE) in water using different nano-catalysts supported laser based photo-oxidation process. For this purpose, nano-structured WO3 catalyst was synthesized in our laboratory and its photocatalytic activity for the demineralization of MTBE in water was compared with different catalysts such as ZnO, TiO2, Fe2O3 and NiO using 355 nm laser radiations generated by the third harmonic of Nd: YAG laser. The effect of laser irradiation time, amount of catalysts and pH were also investigated for the optimization of MTBE removal process. For 60 min of laser exposure time, the overall percentage of MTBE degradation was found to be 93%, 89%, 82%, 80% and 71% for WO3, ZnO, Fe2O3, NiO and TiO2, respectively. In addition the photonic efficiencies of different nano-structured catalysts toward degradation of MTBE were estimated, and they were found to follow the trend of WO3 > ZnO > Fe2O3 > NiO > TiO2.

Morphology and antifungal effect of nano-ZnO and nano-Pd-doped nano-ZnO against Aspergillus and Candida.

The present work was aimed to study the activity of nano-particulated ZnO and nano Pd doped nano-ZnO against Aspergillus and Candida species, commonly contaminating the water supply systems. Micro-ZnO was purchased from the market (Aldrich, USA) while nano ZnO were synthesized using sole gel and precipitation methods and their morphology was determined using XRD and TEM techniques. The average grain size of nano-ZnO estimated by these techniques was 30 nm and 20 nm, respectively. The doping of nano-ZnO with 5 % Pd was achieved by a thermal decomposition method and its morphology; as characterized by XRD, TEM and FESEM techniques; gave an average grain size of 35 nm. Serial dilutions of nano-ZnO doped with 5 % Pd, pure nano-ZnO and micro-ZnO (as a control) were prepared from 10 mg/mL stock solution of each in dermasel agar (OXOID), inoculated with standard strains of Candida albicans and Aspergillus niger and incubated at 37°C for 24 and 48 hours, respectively. Their antimicrobial effect was compared by the minimal inhibitory concentration (MIC), determined as the dilution giving a negligible growth of microorganism. Nano-ZnO doped with 5 % nano-Pd, pure nano-ZnO and micro-ZnO, showed antifungal activity against Aspergilus niger with an MIC of 1.25, 2.5 and 5mg/mL, respectively. However, Candida albicans yeasts were relatively resistant to these compounds, with an MIC of 2.5, 5 and 10 mg/mL for Pd doped nano-ZnO, nano-ZnO and micro-ZnO, respectively. Thus nano-ZnO was twice as potent in killing Aspergillus, as compared to its non-nano-counterpart and loading of nano-ZnO with 5 % nano-Pd further increased its activity, four times that of micro-ZnO. Further investigations are needed to confirm the potential use of nano-ZnO and its doping with nano-Pd in the treatment of water supply systems and food preservation.

Laser-based photo-oxidative degradation of methyl tertiary-butyl ether (MTBE) using zinc oxide (ZnO) catalyst.

Laser-induced photo-catalytic process for the removal of MTBE from water has been investigated in this study. We have studied the laser-based photo-oxidation of MTBE using ZnO semiconductor catalysts at 355 nm laser radiation generated by third harmonic of Nd: YAG laser. The effect of laser irradiation time, laser energy power, catalyst amount and pH parameters were investigated for the efficient removal of MTBE from water using ZnO catalyst. It was found that at pH value of 8, 300 mg of ZnO catalyst, 60 minutes laser irradiation time and 200 mJ of laser energy, delivered best results with maximum degradation of MTBE in water.

Determination of trace metals using laser induced breakdown spectroscopy in insoluble organic materials obtained from pyrolysis of plastics waste.

Laser induced breakdown spectroscopy (LIBS) was applied for the detection of trace elements in non-degradable part of plastics known as insoluble organic material, obtained from thermal and catalytic degradation of plastics. LIBS signal intensity for each metal measured in the test sample was unique and different. The capability of this technique is demonstrated by analyzing various trace metals present inside plastics and also compared with ICP results. The metal concentration (ppm) measured with LIBS and verified by ICP for Ag (901), Al (522), Fe (231), Co (628), V (275), Ni (558), Pb (325), Mn (167) and Cd (378) are higher than permissible safe limits.

Identification of different type of polymers in plastics waste.

The main goal of this work was to develop and test advanced techniques for the instant identification of different type of polymers in post-consumer plastics. In order to accomplish this task, infrared (IR), X-ray diffraction (XRD), differential scanning calorimetric (DSC) and laser induced breakdown spectroscopic (LIBS) techniques were applied. The following six model plastics were identified in this study. Low-density polyethylene (LDPE), High-density polyethylene (HDPE), Polypropylenes (PP), Polystyrene (PS), Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC) along with few randomly selected plastics waste such as water bottle and cap, water cups, yogurt container and coke bottle were studied. IR has shown the fingerprinting of polymer types present in plastics waste. The XRD analysis helps to provide characteristic spectral lines whose intensities vary with the type of each constituent polymer. The DSC method provided the different crystalline melting temperature, glass transition, and onset temperature for the peaks and the percent crystallinity data single out different polymers. The ratio of LIBS signals intensities of carbon and hydrogen atoms were employed for the finger printing of the different family of plastics. The combined use of IR, XRD, DSC and LIBS techniques yielded very useful and effective results for plastic waste management.

Identification of different kinds of plastics using laser-induced breakdown spectroscopy for waste management.

Laser-Induced Breakdown Spectroscopy (LIBS) was applied for the identification of various kinds of plastics for management and recycling of plastic waste. In order to fingerprint these plastics, a laser-produced plasma emission was recorded for spectral analysis of various kinds of plastics. The plasma was generated by focusing a Nd:YAG laser radiation at wavelength = 1064 nm having laser energy = 40 mJ. The 6 main family of plastics tested are: Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polypropylenes (PP), Polystyrene (PS), Polyethylene Terephthalate (PET) and Polyvinyl chloride (PVC). The capability of this technique is demonstrated by the analysis of the major constituents carbon and hydrogen present in polymer matrices. The LIBS signal intensity measured for carbon and hydrogen was detrimental for the fingerprinting of various kinds of plastics. The C/H line intensity ratio was 1.68, 1.51, 1.42, 1.16, 1.01 and 0.91 for HDPE, LDPE, PS, PP, PET and PVC respectively. The detection limits of carbon and hydrogen were found to be approximately 6 micro g/g by applying 20 laser shots. The unique features of LIBS are: it is a simple, rapid, remote, real-time analysis without sampling requirements. The study demonstrated that LIBS could be applied as a best tool for sorting out different kinds plastics on a fast scale for waste management. The health hazards of different kinds of plastics are also described.