Bimetallic nanoparticles (NPs) play a pivotal role in promoting high activity and selectivity towards various industrially important reactions in comparison to single metal NPs due to their modulated electronic and surface properties. Herein, we report the synthesis of non‐precious CoCu NPs, which serve as an excellent catalyst for the selective oxidation of a wide range of electronically diverse benzyl alcohols to benzaldehydes, in the presence of tert‐butyl hydroperoxide (TBHP) as an oxidant at room temperature. The excellent catalytic activity of CoCu NPs is ascribed to a two‐fold synergistic effect arising from the combination of enhanced peroxide decomposition, active Co2+ catalyst regeneration driven by the faster redox processes (between Co3+ and Cu+), and a feasible cobalt dimerisation‐regeneration process. The recoverability and reusability of CoCu NPs are also demonstrated. With the merits of low‐cost and recyclable catalysis under mild conditions, the present catalyst represents an efficient and potential alternative to precious metal catalysts.

CdS quantum dots (QDs), synthesized by a sol–gel method, exhibit significantly Stokes shifted bright photoluminescence (PL), predominantly from the trap states. Surprisingly, the PL decay at the emission maximum is single-exponential. This is an unusual observation for as-prepared QDs and indicates a narrow distribution in the nature of trap states. A closer look reveals an additional fast component for the decays at shorter emission wavelengths, presumably due to the band edge emission, which remains elusive in the steady-state spectra. Indeed, a significantly narrower and blue-shifted emission band is observed in the decay-associated spectra. The contribution of this component to the steady-state PL intensity is shown to be overwhelmed by that of the significantly stronger trap emission. Exciton dynamics in the quantum dots is elucidated using transient absorption spectra, in which the stimulated emission is observed even at low pump power.

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Relaxation dynamics of plasmons in AuÀ SiO 2 core-shell nanoparticles have been followed by femtosecond pump-probe technique. The effect of excitation pump energy and surrounding medium on the time constants associated with the hot electron relaxation has been elucidated. A gradual increase in the electron-phonon relaxation time with pump energy is observed and can be attributed to the higher perturbation of the electron distribution in AuNPs at higher pump energy.Variation in time constants for the electron-phonon relaxation in different solvents is rationalized on the basis of their thermal conductivities, which govern the rate of dissipation of heat of photoexcited electrons in the nanoparticles. On the other hand, phonon-phonon relaxation is found to be much less effective than electron-phonon relaxation for the dissipation of energy of the excited electron and the time constants associated with it remain unaffected by thermal conductivity of the solvent.

The complicated photophysics of wide variety of defects existing in silica (SiO 2 ) layer of nanometer thickness determines widespread photoluminescence bands of Si/SiO 2 based system as well as SiO 2 nanoparticles (NPs) for their applications in photovoltaic and optoelectronic devices. This review attempts to summarize different photophysical processes in pure SiO 2 NPs. Moreover, these NPs also act as scaffolds for various guest molecules to perform their specific functions. Guest fluorophore molecules when trapped inside pores of SiO 2 NPs exhibit a different photodynamics than free state, which opens up several important applications of hybrid SiO 2 NPs in artificial photosynthesis, sensing, biology and optical fiber.