Among different nitro compounds, trinitrophenol (TNP) is the most common constituent to prepare powerful explosives all over the world. A few works on the detection of nitro explosives have already been reported in the past few years; however, selectivity is still in its infant stage. As all the nitroexplosives are highly electron deficient in nature, it is very difficult to separate one from a mixture of different nitro compounds by the usual photoinduced electron transfer (PET) mechanism. In the present work, we have used a bright luminescent, 2,6-diamino pyridine functionalized graphene oxide (DAP-RGO) for selective detection of TNP in the presence of other nitro compounds. The major advantage of using this material over other reported materials is not only to achieve very high fluorescence quenching of ∼96% but also superior selectivity >80% in the detection of TNP in aqueous medium via both fluorescence resonance energy transfer and PET mechanisms. Density functional theory calculations also suggest the occurrence of an effective proton transfer mechanism from TNP to DAP-RGO, resulting in this tremendous fluorescence quenching compared to other nitro compounds. We believe this graphene based composite will emerge a new class of materials that could be potentially useful for selective detection, even for trace amounts of nitro explosives in water.

Chemically synthesized amorphous MoSx quantum dots show excellent HER activity in neutral medium during 12 h of electrolysis.

Extraction of hazardous heavy metals like As, Hg, Cd, Cr(VI), etc. for water purification is a great challenge. Exploiting the large surface area of graphene, in the present work, we have synthesized a UV-active 2,6-diamino pyridine-reduced graphene oxide (DAP-RGO) composite to remove Cr(VI) from acidic water solution. Here, the presence of an extra pyridinic-nitrogen lone pair facilitates the removal efficiency of excess Cr(VI) [500 mg L À1 in 3 h only] over reported results so far. In addition to that, the unique advantage of this UV-active material is the enhancement of removal efficiency by 18% at a higher pH value. We believe that this study will bring forth a new class of UV-active graphene based adsorbents with remarkably high removal efficiency for toxic heavy metals from waste-water in future.

Rapid and selective detection of nitro explosives is one of the most promising issues concerning global security. Intensive research has already been carried out, however, the selectivity is still lacking. In the present work, water soluble MoS 2 quantum dots (QDs) are synthesized through a bottom-up approach using (NH 4 ) 6 Mo 7 O 24 Á4H 2 O and Na 2 S as molybdenum and sulfur sources, respectively, and 1,4-diaminobutane as the capping agent. The as-synthesized QDs detect 2,4,6-trinitrophenol (TNP) selectively up to 2.04 ppm and the selectivity reaches 490% which is remarkably higher than the earlier results. In addition to predominant electron transfer (ET) that occurs mostly in fluorescence quenching processes, Forster resonance energy transfer (FRET) also occurs here. As a result of the occurrence of both these ET and FRET processes, high selectivity is achieved for the present samples. The unique advantage of using QDs is the tuning of photoluminescence as a function of dot size to become comparable with the absorption spectra of the TNP to perform the FRET mechanism.

Selective detection of either mercury (Hg2+) or iodide (I-) ion using fluorescence turn-on or turn-off processes is an important area of research. In spite of intensive research, simultaneous detection of both mercury and iodide using fluorescence turn-off-on processes, high sensitivity and theoretical support concerning the mechanisms are still lacking. In the present work, graphene oxide is functionalized by thymine to realize simultaneous detection of both Hg2+ and I- selectively using fluorescence turn-off-on mechanism. Ultra high sensitivity to the extent of ppb level exploiting large surface area of graphene is achieved. DFT calculations also assist to realize the detailed mechanisms involving this PL quenching and also its regain during sensing of these ions in aqueous solution.