Bhaskar Garg

CuxAgyInzZnkSm solid solutions customized with RuO2 or Rh1.32Cr0.66O3 co-catalyst display visible light-driven catalytic activity for CO2 reduction to CH3OH

CuxAgyInzZnkSm solid solutions, customized with RuO2 or Rh1.32Cr0.66O3 co-catalyst with a small energy band gap <2 eV were studied for photocatalytic CO2 reduction to CH3OH under visible light. Significantly, 118.5 µmol g−1 h−1CH3OH yield was obtained with RuO2/Cu0.30Ag0.07In0.34Zn1.31S2 under hydrogen effect.

Sulfonated graphene as highly efficient and reusable acid carbocatalyst for the synthesis of ester plasticizers

Plasticizers are well known for their effectiveness in producing flexible plastics. The automotive, plastic and pharmaceutical industries, essential to a healthy economy, rely heavily on plasticizers to produce everything from construction materials to medical devices, cosmetics, children toys, food wraps, adhesives, paints, and ‘wonder drugs’. Although H2SO4 is commonly used as commodity catalyst for plasticizer synthesis it is energy-inefficient, non-recyclable, and requires tedious separation from the homogeneous reaction mixture resulting in abundant non-recyclable acid waste. In this study, for the first time, we report an efficient synthesis of ester plasticizers (>90% yields) using sulfonated graphene (GSO3H) as an energy-efficient, water tolerant, reusable and highly active solid acid carbocatalyst. The hydrothermal sulfonation of reduced graphene oxide with fuming H2SO4 at 120 °C for 3 days afforded GSO3H with remarkable acid activity as demonstrated by 31P magic-angle spinning (MAS) NMR spectroscopy. The superior catalytic performance of GSO3H over traditional homogeneous acids, Amberlyst™-15, and acidic ionic liquids has been attributed to the presence of highly acidic and stable sulfonic acid groups within the two dimensional graphene domain, which synergistically work for high mass transfer in the reaction. Furthermore, the preliminary experimental results indicate that GSO3H is quite effective as a catalyst in the esterification of oleic and salicylic acid and thus may pave the way for its broad industrial applications in the near future.

Waste chicken eggshell as low-cost precursor for efficient synthesis of nitrogen-doped fluorescent carbon nanodots and their multi-functional applications

A novel one-step top-down method is developed for the efficient synthesis of nitrogen-doped carbon nanodots (NCNDs) by using calcination treatment of waste chicken eggshell as resources. Based on the usage of urea as a dopant, the as-synthesized NCNDs are referred to as NCND 1 (no dopant) and NCND 2. The structural and composition analysis indicate that NCND 2 possesses a mean particle diameter of 2.6 nm and an amorphous carbon structure with a lattice spacing of 0.38 nm. Despite having a low N-content (∼4%), the as-prepared NCND 1 was also found to exhibit excellent photoluminescent properties, low cytotoxicity and could be effectively used for bioimaging, in conjunction with NCND 2. The multi-functional capability of NCND 2 is further demonstrated for stamping, printing, and forensic applications. This work may pave the way for employing carbonaceous waste materials as potential precursors in the synthesis of carbon nanomaterials for wide technological applications.

A phenothiazine-based colorimetric chemodosimeter for the rapid detection of cyanide anions in organic and aqueous media

A novel, phenothiazine-based chemodosimeteric probe PCP 1 has been developed and studied as a cyanide selective indicator in organic and aqueous media. Complete colour bleaching was observed due to nucleophilic addition of cyanide to the tricyanovinyl moiety of PCP 1, which results in the disruption of the extended conjugate and turn-off the intramolecular charge transfer process.

Graphene-based nanomaterials as molecular imaging agents.

Molecular imaging (MI) is a noninvasive, real-time visualization of biochemical events at the cellular and molecular level within tissues, living cells, and/or intact objects that can be advantageously applied in the areas of diagnostics, therapeutics, drug discovery, and development in understanding the nanoscale reactions including enzymatic conversions and protein-protein interactions. Consequently, over the years, great advancement has been made in the development of a variety of MI agents such as peptides, aptamers, antibodies, and various nanomaterials (NMs) including single-walled carbon nanotubes. Recently, graphene, a material popularized by Geim & Novoselov, has ignited considerable research efforts to rationally design and execute a wide range of graphene-based NMs making them an attractive platform for developing highly sensitive MI agents. Owing to their exceptional physicochemical and biological properties combined with desirable surface engineering, graphene-based NMs offer stable and tunable visible emission, small hydrodynamic size, low toxicity, and high biocompatibility and thus have been explored for in vitro and in vivo imaging applications as a promising alternative of traditional imaging agents. This review begins by describing the intrinsic properties of graphene and the key MI modalities. After which, we provide an overview on the recent advances in the design and development as well as physicochemical properties of the different classes of graphene-based NMs (graphene-dye conjugates, graphene-antibody conjugates, graphene-nanoparticle composites, and graphene quantum dots) being used as MI agents for potential applications including theranostics. Finally, the major challenges and future directions in the field will be discussed.

Rapid identification of trimethyl and triethyl amines using sulphonic acidic ionic liquids: A time-of-flight secondary ion mass spectrometry study of fragmentation reactions.

The time-of-flight secondary ion mass spectrometry (TOF-SIMS) has emerged as a powerful tool for the unswerving detection of biomolecules, in particular, proteins and peptides. To date, there is very little information available on the direct determination of trimethyl/triethyl amines using TOF-SIMS. One major hurdle in this regard is an ultrahigh vacuum system, usually needed in TOF-SIMS, which hampers its usability to trimethyl/triethyl amines owing to their high evaporation rate. We designed an efficient and sensitive protocol for rapid identification and sensitive determination of tertiaryalkyl amines using TOF-SIMS. The amines were derivatized by reaction with 1,4-butane sultone and sulphuric acid sequentially to afford the corresponding sulphonic acidic ionic liquids (ILs). The TOF-SIMS analysis of these task-specific ILs (TSILs) was carried out in both positive and negative polarity. The positive ion mass spectra of TSILs showed sharp fragmented peaks for tertiaryalkyl amines at typical level and up to 10ppm. The possible mechanism for different fragmentation pathways in positive polarity was discussed.

Tricyanovinyl substituted calix[4]pyrrole: an old yet new potential chemosensor for biothiols

A calix[4]pyrrole bearing tricyanovinyl motif as recognition and chromophoric tag has been evaluated as an effective and selective chemosensor for cysteine, homocysteine, and glutathione. The unique changes in the absorption spectra as well as discriminative colorimetric changes in the presence of these biothiols are the attractiveness of this colorimetric assay.