Noble metal nanoparticles loaded smart polymer microgels have gained much attention due to fascinating combination of their properties in a single system. These hybrid systems have been extensively used in biomedicines, photonics, and catalysis. Hybrid microgels are characterized by using various techniques but UV/Vis spectroscopy is an easily available technique for characterization of noble metal nanoparticles loaded microgels. This technique is widely used for determination of size and shape of metal nanoparticles. The tuning of optical properties of noble metal nanoparticles under various stimuli can be studied using UV/Vis spectroscopic method. Time course UV/Vis spectroscopy can also be used to monitor the kinetics of swelling and deswelling of microgels and hybrid microgels. Growth of metal nanoparticles in polymeric network or growth of polymeric network around metal nanoparticle core can be studied by using UV/Vis spectroscopy. This technique can also be used for investigation of various applications of hybrid materials in catalysis, photonics, and sensing. This tutorial review describes the uses of UV/Vis spectroscopy in characterization and catalytic applications of responsive hybrid microgels with respect to recent research progress in this area.
The title compounds diacylaminoquinazolinones (DAQs) are enantioselective acylation agents for amines and a detailed study of their stereostructures was undertaken with the aim of understanding how this enantioselectivity arises. The N-N bond in these DAQs is a chiral axis. Even where both N-acyl groups are (S)-2-acetoxypropanoyl, the N-N bond is still a chiral axis because in the most stable conformation of the planar imide moiety, one exo/endo orientation of the carbonyl groups is much preferred over the alternative (endo/exo) as revealed by NMR spectroscopy. A conformational preference within the 2-acetoxypropanoyl grouping accounts for the presence of a single exo/endo conformation in solution for some of these DAQs (see above) but an interconverting exo/endo endo/exo mixture for others. Where a single exo/endo conformation is present in solution, evidence is presented that this closely resembles the X-ray determined crystal structure. A mechanism for the second acylation step to form these DAQs is proposed, which involves preliminary O-acylation of the 3-(monoacylamino)quinazolinone.
Carbon atoms have the potential to produce a variety of fascinating all-carbon structures with amazing electronic and mechanical properties. Over the last few decades, several efforts have been made using experimental and computational techniques to functionalize graphene, carbon nanotubes and fullerenes for potential use in modern hi-tech electronic, medicinal, optical and nonlinear optical (NLO) applications. Since photons replaced electrons as a carrier of information, the field of NLO material design has drawn immense interest in contemporary materials science. There have been several reports of bridging the gap between the exciting fields of carbon nanomaterials and NLO materials by functionalizing carbon nanomaterials for potential NLO applications. In contrast to previous reports of the design of third-order NLO materials using conventional closed-shell materials, a novel strategy using open-shell diradical molecular systems has recently been proposed. Quantum chemically, diradical character is explained in terms of the instability of the chemical bonds in open-shell molecular systems. Interestingly, several carbon nanomaterials, which naturally possess open-shell singlet configurations, have recently gained momentum in the design of these classes of open-shell NLO materials with excellent NLO properties, stability and diversity. The present review establishes a systematic sequence of different studies (spanning over two decades of intense research efforts), starting from the simplest theoretical two-site diradical model, continuing to its experimental and theoretical realization in actual chemical systems, and finally applying the abovementioned model/rule to novel carbon nanomaterials to tune their NLO properties, particularly their second hyperpolarizability (γ). In the present report, we highlight several recent efforts to functionalize carbon nanomaterials by exploiting their open-shell diradical character to achieve efficient third-order NLO properties. Several issues and opportunities are discussed, including the inherited disadvantages of both experimental (the high reactivity and short life of diradical compounds) and quantum (need for multi-reference methodology) techniques when dealing with carbon nanomaterials. A comparative analysis of several quantum chemical investigations, along with contemporary experimental results, will be performed to emphasize the core issues and opportunities related to carbon nanomaterials with singlet open-shell diradical character. Thus, the present review will highlight carbon nanomaterials with diradical/biradical character for their prospective applications in the NLO field.
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