With regard to perovskite solar cells (PSCs), a zinc oxide (ZnO) planar architecture has significant advantages from the upscaling perspective in terms of cost effectiveness and low-temperature processing compared to architectures with a mesoporous titanium dioxide (TiO 2 ) layer. Nevertheless, the perovskite (PVK) materials are unstable on a ZnO electron transport layer (ETL) during the annealing process. Herein, we discovered that the PVK material on top of the ETL changes to lead iodide (PbI 2 ) because of the presence of oxygen agents on the surface of ZnO. To tackle this issue, a hybrid photoelectrode of ZnO/graphene quantum dots (GQDs) is prepared and used as an ETL. As a result, green synthesized GQDs not only passivate the oxygen agents on the surface of the ZnO but also extract electrons rapidly from the PVK film to decrease the recombination of electron−hole pairs. Herein, findings reveal that PSC on ZnO:GQD ETL shows a power conversion efficiency (PCE) of up to 17% on fluorine tin oxide (FTO) under AM1.5G illumination. Consequently, the introduction of multifunctional GQD as an additive in ZnO ETL in PSCs displays a new and efficient tool in terms of environmental impact and economic feasibility for PSC commercialization.

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Hole transport material-free perovskite solar cells (HF-PSCs) offer low-cost photovoltaic devices. For development and commercialization, they are more attractive than the expensive HTLcontained perovskite solar cells. Herein, we focused on enhancing the stability and efficiency of HF-PSCs with the malonic acid (MA) addition to the methylammonium lead iodide. The introduced additive increases the perovskite crystallinity and assembles a perovskite layer with larger grains along with fewer surface defects. In addition, the MA-modified HF-PSCs show suppressed charge recombination within devices, and a lower charge trap density has been obtained for them. A considerable power conversion efficiency of 14.14% is achieved for MA-modified HF-PSCs, higher than the performance of 11.88% for the untreated HF-PSCs. Finally, MA-based HF-PSCs show higher shelf stability than the control HF-PSCs. It is because the MA-modified perovskite layer with passivated grain boundaries is better at repelling water.

The raw-SWNTs and raw-MWNTs were chemically oxidized with a mixture of sulfuric acid and nitric acid under ultrasonic vibration. The functionalized-SWNTs (F-SWNTs) and functionalized-MWNTs (F-MWNTs) were characterized by using ultra violet-visible spectrophotometer, X-ray diffraction, and field emission scanning electron microscopy (FESEM). The antibacterial efficiency of SWNTs and MWNTs towards Escherichia coli (E. coli) as gram-negative bacteria was evaluated via viable count method and fluorescence microscopy. The results of viable count method showed that the SWNTs and MWNTs have higher inhibitory effect after being treated with H2SO4/HNO3.The E. coli images under fluorescence microscopy exhibited that almost red color for dead cells, which confirms the efficient lethal ability of F-SWNTs and F-MWNTs.

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Zinc oxide-silver (ZnO–Ag), and zinc oxide-gold (ZnO–Au) nano-composites were prepared through wet chemical process and laced into single-walled carbon nanotubes (SWCNTs) to yield ZnO–Ag-SWCNTs, and ZnO–Au-SWCNTs hybrids. These nano-composite-laced SWCNTs hybrids were characterized using Raman spectroscopic, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The hybrids were evaluated for their effects on phagocytic cells and bactericidal activity against the gram-negative bacteria E. coli. Their phagocytic cell activities and intracellular killing actions were found to be significantly increased, as the ZnO–Ag-SWCNTs and ZnO–Au-SWCNTs nano-hybrids induced widespread clearance of Escherichia coli. An increase in the production of reactive oxygen species (ROS) also led to upregulated phagocytosis, which was determined mechanistically to involve the phagocyte NADPH oxidase (NOX2) pathway. The findings emphasized the roles of ZnO–Ag- and ZnO–Au-decorated SWCNTs in the prevention of bacterial infection by inhibiting biofilm formation, showing the potential to be utilized as catheter coatings in the clinic.