Graphene quantum dots (GQD) are nanosized fragments of graphene with finite band gap. Thus, GQDs show excellent photoluminescence (PL) and also possess good electrochemical properties. In the present study, we synthesized GQDs via hydrothermal (HT) method using Graphene oxide as prepared from improved Hummer's method as a precursor with several modifications. The effect of the variation in the photoluminescence and electrochemical properties of the as‐prepared GQDs were studied. Average particle size of the as‐synthesized GQDs was roughly 30 nm and produced blue PL on excitation with a wavelength of 365 nm. On reacting the GQDs with Cupric Nitrate and Cobalt Nitrate in separate batches, a significant decrease in the intensity of PL was observed. This quenching of PL of GQDs has been utilized in the qualitative estimation of Metal ion (Cu2+ and Co2+) species in aqueous media.

In the continuous casting process, the tundish acts as a continuous molten steel distribution vessel. The importance of the tundish during the molten steel delivery becomes more significant when it supplies liquid steel to more than one mould. In the present work, a water model of a six strand billet caster tundish has been used to study the effect of strand blockage on the residence time distribution (RTD) characteristics at the strands. All the experiments were performed under steady state conditions. Potassium chloride was used as a tracer for the study. The effects of blockage on the strand dissimilarity among the open strands were also studied. Both single and dual strand blockage experiments were performed. Blockage of strands deteriorated the RTD characteristics at the open strands. The results reveal the most preferred options for strand blockage when the plant operation needs to do so.

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The photoluminescence of graphene quantum dots (GQD) is widely explored for sensory applications. Among various metal ions to be detected in aqueous bodies, Ca2+ ions are often neglected which is evident from the lack of literature. However, owing to booming industrialization, the available potable water is mostly crossing the prescribed hardness limits. Presented report summarize the synthesis of GQD via modified hydrothermal cutting of graphene oxide, which was further employed for sensing Ca2+ ions in hard water samples. The as synthesized GQD exhibited its characteristic blue photoluminescence on excitation with longwave UV (λ ≈ 365 nm) which was suppressed on the introduction of Ca2+ ions. The GQD as photoluminescent probe determined the concentration of Ca2+ ion in water with an accuracy of 96.74% ± 3.26%. The LOD of the reported method was found to be 5 μM and it was sensitive towards Ca2+ ions in the presence of interfering ions such as Al3+, Mg2+, and K+ which are commonly found in hard water samples. Therefore, the determination of hardness of water w.r.t Ca2+ using GQD based PL turn off sensing is a quick, viable and economical method.

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The resonance energy transfer (RET) from tryptophan present in bovine serum albumin (BSA) to two dimensional (2D) nanomaterials has been reported.

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This paper numerically investigates the heat transfer enhancement using rectangular winglet pairs in a fin-and-tube type heat transfer surface having five inline rows of tubes. The influence of number of winglets, attack angles of the winglets, and their location has been analyzed under laminar flow conditions with Reynolds number ranging 400–1500. To account for the combined effect of heat transfer enhancement and pressure drop penalty, an enhancement factor is also discussed by changing the winglet pair's number and location. The numerical results show that pressure drop can be reduced significantly by placing the winglet more toward the exit of the flow channel. Streamwise distance and spanwise distance of the winglet pairs have been investigated for maximum enhancement factor. The numerically obtained results show that the winglets number and their placement at different locations have a major influence on enhancement factor. The results show that both the heat transfer and the pressure drop increase with an increase in attack angle of the winglets and best angle for the highest enhancement factor has been found out. Correlations have been developed for streamwise distance, spanwise distance, and angle of attack for different range of Reynolds numbers.