The recent advances in perovskite solar cells (PSCs) created a tsunami effect in the photovoltaic community. PSCs are newfangled high-performance photovoltaic devices with low cost that are solution processable for large-scale energy production. The power conversion efficiency (PCE) of such devices experienced an unprecedented increase from 3.8 % to a certified value exceeding 20 %, demonstrating exceptional properties of perovskites as solar cell materials. A key advancement in perovskite solar cells, compared with dye-sensitized solar cells, occurred with the replacement of liquid electrolytes with solid-state hole-transporting materials (HTMs) such as 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), which contributed to enhanced PCE values and improved the cell stability. Following improvements in the perovskite crystallinity to produce a smooth, uniform morphology, the selective and efficient extraction of positive and negative charges in the device dictated the PCE of PSCs. In this Review, we focus mainly on the HTMs responsible for hole transport and extraction in PSCs, which is one of the essential components for efficient devices. Here, we describe the current state-of-the-art in molecular engineering of hole-transporting materials that are used in PSCs and highlight the requisites for market-viability of this technology. Finally, we include an outlook on molecular engineering of new functional HTMs for high efficiency PSCs.

Graphitic C3 N4 (g-C3 N4 ) is used as a low-cost organic oxygen evolution reaction (OER) electrocatalyst. The integration of ultrathin g-C3 N4 nanosheets with graphene leads to g-C3 N4 /graphene composites with high OER activity and good durability. X-ray photoelectron spectroscopy (XPS) studies suggest that the OER activity results from pyridinic-N-related active sites. This catalyst provides an alternative to OER catalysts based on transition metals.

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The development of an analytical method for selective and sensitive detection of chlortetracycline (CTC), an often overused broad spectrum antibiotic, is important and challenging in environmental and health monitoring. This paper reports a zinc based metal–organic framework of pyromellitic acid (Zn-BTEC), which has been found to greatly enhance the aggregation-induced emission (AIE) of chlortetracycline. The unique emission response of CTC on Zn-BTEC has been extensively examined and applied for the sensitive detection of CTC on the basis of fluorescence intensity of AIE, and a limit of detection (LOD) was estimated to be 28 nM. A rational mechanism has been proposed based on the porous structure of Zn-BTEC, and the CTC molecules would defuse into the rigid MOF structure and assemble or aggregate, leading to fluorescence enhancement of CTC. Interestingly, the Zn-BTEC materials could discriminate CTC from other TC antibiotics with high selectivity. We have further demonstrated that the Zn-BTEC materials are successfully applied for the sensitive and selective determination of CTC in real samples of fish and urine.

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Design and development of potential pyruvate dehydrogenase kinase 3 (PDK3) inhibitors have gained attention because of their possible therapeutic uses in lung cancer therapy. In the present study, the binding affinity of naturally occurring alkaloids, hordenine, vincamine, tryptamine, cinchonine, and colcemid was measured with PDK3. The molecular docking and fluorescence binding studies suggested that all these compounds show a considerable binding affinity for PDK3. Among them, the affinity of hordenine to the PDK3 was excellent (K = 106 M−1) which was further complemented by isothermal titration calorimetric measurements. Hordenine binds in the active site pocket of PDK3 and forms a significant number of non-covalent interactions with functionally important residues. All-atom molecular dynamics (MD) simulation study suggested that the PDK3-hordenine complex is stabilized throughout the trajectory of 100ns and leads to fewer conformational changes. The enzyme inhibition studies showed that hordenine inhibits the activity of PDK3 with an IC50 value of 5.4 µM. Furthermore, hordenine showed a cytotoxic effect on human lung cancer cells (A549 and H1299) with an admirable IC50 value. However, it did not inhibit the growth of HEK293 cells up to 200 µM, indicating its non-toxicity to non-cancerous cell lines. In summary, our findings provide the basis for the therapeutic implication of hordenine and its derivatives in lung cancer and PDK3-related diseases after required in vivo validation.

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