Bacterial infections instigated by antibiotic-resistant bacteria are considered perilous health threats in today’s world due to their fast-increasing nature and the fewer availability of new treatment strategies. The properties of nanomaterials triggered by external stimuli are considered an encouraging technique for the remediation of antibacterial infectious diseases by producing photoinduced reactive oxygen species (ROS). Light-mediated treatment using zinc oxide (ZnO)-based nanohybrids leads the field with high interest in terms of sensitization of antibiotics and their targeted delivery. Moreover, the dual sensitization in a hybrid system could produce more efficacy as this phenomenon has been implemented in dye sensitized solar cells and photocatalysis. However, most of those hybrids are complicated and non-biocompatible. The present study highlights a tri-hybrid by encapsulating tetracycline (TC) in Au nanoparticle-decorated ZnO nanoparticles. The composition and morphology of the samples were characterized by electron microscopy, ultrafast optical spectroscopy, and density functional theory-based techniques. The dual sensitization in the tri-hybrids leads to enhanced antimicrobial activity against Gram-positive Staphylococcus hominis bacteria due to immense ROS under white light irradiation. The Förster resonance energy transfer from TC to Au and the excited-state photo-electron transfer process in the Au_ZnO-TC tri-hybrid system trigger a huge charge separation, which enhances production of ROS. Due to such a huge ROS production capability, the tri-hybrid shows a significant antibacterial action. Moreover, the Au nanoparticle-decorated ZnO is capable of destroying excess antibiotics, which potentially reduces the chance of development of antibiotic resistance. Overall, the study demonstrates a promising aspect that could be beneficial for manifold biological applications.
Excess consumption of fluoride through drinking water and its detrimental effects on human health have been a serious global concern. Therefore, frequent monitoring as well as quantitative determination of fluoride ion (F -) concentration in aqueous media is of vital importance. Herein, we have developed a facile and highly sensitive spectroscopic technique for selective detection of Fin aqueous media using aluminium phthalocyanine chloride (AlPc-Cl) as a sensor. The absorbance as well as steady-state fluorescence intensity of AlPc-Cl has been found to decrease in presence of Fwhich has been used as a marker for the determination of fluoride ion concentration in water. The structural change in AlPc-Cl after addition of Fhas been thoroughly studied by using 19 F NMR (Nuclear Magnetic Resonance) spectroscopy. Our detailed steady-state as well as time-resolved fluorescence studies reveal that the quenching mechanism is static in nature due to ground state complexation in between Fand AlPc-Cl molecules. The response of the sensor is found to be linear over the Fconcentration regime from 0 to 6 parts per million (ppm) with a detection limit of 0.05 ppm. Additionally, it shows an excellent selectivity as well as an insignificant change in sensitivity even in the presence of interfering iron and aluminium ions. Based on the detailed photophysical study, we have further developed a low cost and portable prototype device which shows an excellent sensitivity with the detection limit of 0.10 ppm. This prototype device has a high prospect for real-time monitoring of fluoride ion concentration especially in remote areas.
Plasmonic nanoparticles are of great importance owing to their highly responsive 'Localized Surface Plasmon Resonance' (LSPR) behaviour to self-agglomeration/ aggregation leading to the development of various nanosensors. Herein we demonstrated the definite self-assembly of citrate functionalized silver nanoparticles (AgNPs) into a one-dimensional linear chain in presence of charged lead ions (Pb 2+ ), one of the most toxic heavy metal pollutants. We have explored detail mechanism using a variety of spectroscopic tools and electron microscopy. The self-aggregation of AgNPs leads to the generation of new LSPR modes due to coupling of nearby existing modes. The conclusion of our experimental findings is duly supported by our developed numerical modelling based on the quasi-static approximation that the generated new LSPR modes are solely due to formation of chain-like aggregation of AgNPs. We have also monitored the LSPR spectra in presence of other metal ions, however, only Pb 2+ found to give such unique self-assembled geometry may due to its high interaction affinity with citrate. These findings play a key role for citrate functionalised AgNPs to be used as a low cost highly selective and sensitive lead ion sensor for potential application in industrial lead pollution monitoring. We have further varied several sensor parameters such as AgNPs size, concentration and the allowed reaction time for it to be practically implemented as an efficient lead sensor meeting the Environmental Protection Agency recommendations.
A transmetalation mechanism for the removal of toxic Hg from a Hg–curcumin complex and the detection of the separated free Hg ions using the SPR band quenching of Ag-nanoparticles is shown.
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