• GOUTAM DE

      Articles written in Journal of Chemical Sciences

    • Tuning of Ag-SPR band position in refractive index controlled inorganic-organic hybrid SiO2-PEO-TiO2 films

      Samar Kumar Medda Moumita Mitra Goutam De

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      Inorganic (silica-titania)-organic (polyethylene oxide) hybrid films with variable refractive index (RI) values were synthesized and Ag nanoparticles were generated in situ inside such hybrid films to develop coloured coatings specially on plastic substrates. The hybrid films and the corresponding Agincorporated films were prepared from sols derived from a mixture of silicon tetraethoxide (STE), 3-(glycidoxypropyl)trimethoxysilane (GPTMS), titanium tetraisopropoxide (TTIP) and silver nitrate following a sol-gel dip-coating method and cured at low temperature (90°C), followed by UV treatment with an energy equivalent to $5.3 \pm 0.1$ J cm-2. The equivalent SiO2: SiO1.5(CH2)3OCH2CH(CH2)O : TiO2: Ag molar ratios (nominal) of the final cured films are varied in the ranges (67.9-0) : 29.1 : (0-67.9) : 3. The refractive index values of the cured hybrid films were found to be increased systematically from 1.475 to 1.710 with increasing Ti-component. The Ag-SPR peak, in case of silica-polyethylene oxide host (RI = 1.475), observed at 419 nm, gradually red-shifted to 497 nm upon increasing the Ticomponent (equivalent TiO2 content 67.9 mol%; RI = 1.710) of the film. As a consequence, a systematic change of Ag-SPR position yielded yellow, yellowish-orange, orange, brownish-orange and orangish-brown coloured coatings.

    • Carboxylic acid terminated, solution exfoliated graphite by organic acylation and its application in drug delivery

      KOUSHIK BHOWMIK AMRITA CHAKRAVARTY U MANJU GOUTAM DE ARNAB MUKHERJEE

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      Graphite nanosheets are considered as a promising material for a range of applications from flexible electronics to functional nanodevices such as biosensors, intelligent coatings and drug delivery. Chemical functionalizationof graphite nanosheets with organic/inorganic materials offers an alternative approach to control the electronic properties of graphene, which is a zero band gap semiconductor in pristine form. In this paper, we report the aromatic electrophilic substitution of solution exfoliated graphite nanosheets (SEGn). The highly conjugated π-electronic system of graphite nanosheets enable it to have an amphiphilic characteristic in aromatic substitution reactions. The substitution was achieved through Friedel–Crafts (FC) acylation reaction under mild conditions using succinic anhydride as acylating agent and anhydrous aluminum chloride as Lewisacid. Such reaction renders towards the carboxylic acid terminated graphite nanosheets (SEGn–FC) that usually requires harsh reaction conditions. The product thus obtained was characterized using various spectroscopicand microscopic techniques. Highly stable water-dispersed sodium salt of carboxylic acid terminated graphite nanosheets (SEGn–FC-Na) was also prepared. A comparative sheet-resistance measurements of SEGn, SEGn–FC and SEGn–FC-Na were also done. Finally, the anticancer drug doxorubicin (DOX) was loaded on water dispersible SEGn–FC-Na with a loading capacity of 0.266 mg mg−1 of SEGn–FC-Na and the release of DOX from this water-soluble DOX-loaded SEGn–FC-Na at two different temperatures was found to be strongly pHdependent.

    • Influence of C–S interactions on the electrochemical performance of –COOH functionalized MWCNT/S composites as lithium-sulfur battery cathode

      TANUMOY DHAWA SHREYASI CHATTOPADHYAY MONJOY SREEMANY GOUTAM DE SOURINDRA MAHANTY

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      Effective trapping of polysulfides within the carbon cathode host strongly depends on intrinsic C–S interactions. We report herein a systematic study of the influence of S-loading process on C–S interactions in MWCNT/S composites prepared by three commonly used industry-friendly methods, namely, mechanical solidstate mixing, infiltration method from a solution of S in CS2, and chemical deposition by disproportionation reaction of sodium sulfide and sodium thiosulfate. FESEM and TEM studies reveal strikingly different morphologies of the resulting MWCNT/S composites. XPS and Raman studies indicate different extents of recovery of π bonds in MWCNT due to varying degrees of C–S interfacial interactions in the composites. Furthermore, it is found that the C/O atomic ratio in the composites plays a crucial role: the higher the C/O valuethe better is the S-confinement. These subtle physical changes induced by C–S interactions in the composites can be related to electrochemical performance when tested in Li-S coin cells. It is found that the best results (high initial capacity of 1143 mAh g -1 and better capacity retention) could be achieved when the solution infiltration method was used for S-loading. This conclusion is further validated by using activated carbon as S-host.

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