Dipak Sinha

Gamma-induced modifications of polycarbonate polymer

Gamma-induced modifications in polycarbonate polymer have been studied in the dose range of 101–106 Gy. Thin films of polycarbonate have been irradiated with different gamma doses from a Co60 source. To monitor the modifications caused by gamma radiation, FT-IR, differential scanning calorimetry and X-ray diffraction studies have been performed. The studies have indicated that at the dose of 106 Gy, phenolic group forms through scissioning of ester linkage. Though the effect of radiation is most significant at the highest dose, the process of modifications starts at 103 Gy. Scissioning of the polymeric chain initiates a different morphological zone within the polymer matrix, and the polymer becomes more crystalline with increasing dose. Owing to chain scissioning, the mobility of the polymer increases, which in turn reduces the glass transition temperature of the polymer.

Synthesis and Reactivity Studies of a New Reagent, Ethyltriphenylphosphonium Tribromide

A new reagent, ethyltriphenyl phosphonium tribromide (ETPPTB), has been synthesized and studied. Results show that the reagent is quite efficient for various reactions such as organic bominations, acylations, and isothiocyanate preparation.

Microwave-induced reactions: an alternative route for chemical synthesis

In an effort to study the scope of microwave radiation for organic bromination reactions, some reactions were studied using a domestic microwave oven. Results reveal that these radiation-induced reactions are unique in their high yields and that they require extremely short reaction times compared with conventional room-temperature reactions. In these reactions tetrabutyl ammonium tribromide was used as an alternative brominating reagent in order to avoid the chemical hazards associated with liquid bromine (Br2). As all the reactions were successfully carried out in solid state under microwave conditions, the use of solvent was not required. All these aspects make the bromination protocol quite environment friendly.

Adsorption studies of fluoride by activated carbon prepared from Mucuna prurines plant

Activated carbon synthesized from the plant Mucuna prurines have been successfully used to remove fluoride from aqueous solution by adsorption method. Batch method adsorption has been studied and the adsorption was found to be very significant. Almost 96% of fluoride could be removed by adsorption. Adsorption studies of fluoride signify the fact that among the different adsorption model, Langmuir adsorption model seems to be more favorable in the present case. Different parameters like effect ofadsorbent dosage, contact time, pH and initial concentration are studied to understand the adsorption mechanism.

A comparative study of gamma radiation effects on track properties of different PADC detectors

Track properties of gamma-irradiated polyallyldiglycol carbonate (PADC) detectors (Homalite, Pershore and Trastrack) are studied in the dose range of 101–106 Gy. Results show that the bulk and track etch rates of all three types of PADC detector increase at doses higher than 104 Gy. This increase is more pronounced in post-gamma exposed detectors. The change in etch rate ratio (S) for post-gamma exposed PADC–Homalite detectors is more significant when compared with the other detectors. The critical angle for etching shows that etching at a low temperature of 60 °C is more effective, and the critical angle value is decreased to a significant extent for all three types of PADC detectors. Etching efficiency of post-gamma exposed samples is found to be much higher than the pre-gamma exposed sample at the highest dose of 106 Gy. When compared, it was found that of the three PADC detectors, PADC–Homalite detectors seem to be more sensitive to gamma irradiation.

Nanoclusters and nanotubes for swift ion track technology

With interest rising recently in nanostructures of all kinds, attention was also given to etched ion tracks in insulators. The emerging nanopores with a very high aspect ratio enable one to create new functionalities, especially in thin polymeric foils and oxide-on-silicon structures, when combined with electronic, optical, catalytic or sensing materials. These materials are often inserted into the nanopores in the form of nanoparticles for several reasons. On the one hand, quantum effects can easily be exploited in this way, and, on the other hand, tailoring of size and distance of (semi)conducting nanoclusters enables one to obtain any desired conductivity value between insulating and metallic nanocluster/nanopore devices. Also, the very large surface areas of nanoclustered materials may be useful for initiating chemical reactions, e.g. for sensing, catalytic, or medical purposes. Nanotubes may be grown within the nanopores, which enhance the range of possibilities greatly. Potential applications of these strategies are outlined.