In this review, we discuss recent advances of I–III–VI QDs with a major focus on synthesis and biomedical applications; advantages include low toxicity and fluorescent tuning in the biological window.

Off-stoichiometric CuInS₂ quantum dots (CuInS₂, a mixture of In₂S₃/CuInS₂, and a Mn-doped mixture of In₂S₃/CuInS₂) were prepared in a one-pot reaction, and the corresponding sensitized solar cells exhibit promising photovoltaic performances.

Herein, we present the direct aqueous synthesis of manganese (Mn) doped CuInSe₂ (Mn-CISe) quantum dots (QDs) under microwave irradiation to improve the photochemical properties of solar cells. As a result of Mn doping, the narrower bandgap energy of Mn-CISe leads to higher visible light absorption. The Mn-CISe QDs are therefore used as photosensitizers in quantum dot sensitized solar cells (QDSSCs), exhibiting enhanced performance which is dependent on Mn concentration. To the best of our knowledge, this is the first time to construct an Mn-CISe sensitized-TiO₂ photoanode to boost the photovoltaic performance of QDSSCs. The incorporation of Mn into CISe increases short-circuit current, which is ascribed to the effective injection of the excited electrons from QDs into TiO₂ and the consequent higher electron lifetime, likely through a newly formed Mn midgap in the CISe band structure. Compared to the undoped QDs, Mn-CISe QDSSCs show a shorter electron transport time (τ_t) and a longer electron recombination time (τ_r) which are studied by intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy, respectively. In fact, a combination of higher light-harvesting efficiency, slower charge recombination, and a longer electron lifetime gives rise to a maximum photovoltaic performance of 6.28%.

Xanthine oxidase is one of the members of molybdo-enzymes known to catalyze the oxidative hydroxylation of various purine derivatives. The mechanistic transformation of the tetrahedral Michaelis-Menten type complex ((E_OX)-[Mo^(VI)-O_eq-C_CRH]) to the product bound intermediate ((E_OX)-[Mo^(IV)-O_eq-C_CR]) is expected to pass through the tetrahedral transition state complex ((E_OX)-[Mo^(VI)(-O_eq-C_CRH---H_RH---)(=S_Mo)]^#). Although several accounts are made regarding the events taking place at the transition state, they have never been fully explored nor quite understood. Similarly, the description of the formation of O_eq-C_CRH bond, cleavage of C_CRH-H_RH bond, migration of H_RH to S_Mo terminal, and reduction of (E_OX)-Mo^(VI) to (E_RED)-Mo^(IV) was not well understood. In order to understand the events taking place during catalysis, new computational models have been used to perform an electronic structure calculation. The calculations were performed on the active site model compound bound to purine derivatives, mainly 2-hydroxy-6-methyl purine (HMP) that has never been investigated computationally. The transition state modeling also reveals a reactant like transition state for the reaction of HMP with the active site. Understanding the transition state geometry is a prime importance in developing a plausible reaction mechanism. From the four alternative paths, path one has small energy barrier compare to the three alternative paths. Understanding the mechanism may be used in the drug design process. From our mechanistic study HMP favor concerted mechanism rather than step wise mechanism.