This investigation reports the use of agrowaste pomegranate peels as an economical source for the production of fluorescent carbon dots (C-dots) and their potential application as an antimicrobial agent. The carbon dots were prepared through low-temperature carbonization at 200°C for 120 min. The obtained C-dots were found to be small in size and exhibited blue luminescence at 350 nm. Further, the synthesized C-dots were characterized with the help of analytical instruments such as DLS, UV-visible, FT-IR, TEM, and fluorescence spectrophotometer. Antimicrobial activity of the C-dot PP was estimated by the agar diffusion method and MIC. S. aureus and K. pneumoniae are showing susceptibility towards C-dot PP when compared to the standard and showing a moderate activity against P. aeruginosa and resistance towards E. coli. The obtained C dot PPs were found to be around 5-9 nm in size confirmed from DLS analysis and supported by TEM. The synthesized C-dots were investigated to understand their microbial efficiency against pathogens and found to have antimicrobial efficiency. These results suggest that pomegranate peels are a potential source of carbon dots with antimicrobial efficiency.
In the current research, we present a single-step, one-pot, room temperature green synthesis approach for the development of functional poly(tannic acid)-based silver nanocomposites. Silver nanocomposites were synthesized using only tannic acid (plant polyphenol) as a reducing and capping agent. At room temperature and under mildly alkaline conditions, tannic acid reduces the silver salt into nanoparticles. Tannic acid undergoes oxidation and self-polymerization before the encapsulating of the synthesized silver nanoparticle and forms silver nanocomposites with a thick capping layer of poly(tannic acid). No organic solvents, special instruments, or toxic chemicals were used during the synthesis process. The results for the silver nanocomposites prepared under optimum conditions confirmed the successful synthesis of nearly spherical and fine nanocomposites (10.61 ± 1.55 nm) with a thick capping layer of poly(tannic acid) (~3 nm). With these nanocomposites, iron could be detected without any special instrument or technique. It was also demonstrated that, in the presence of Fe3+ ions (visual detection limit ~20 μM), nanocomposites aggregated using the coordination chemistry and exhibited visible color change. Ultraviolet-visible (UV–vis) and scanning electron microscopy (SEM) analysis also confirmed the formation of aggregate after the addition of the analyte in the detection system (colored nanocomposites). The unique analytic performance, simplicity, and ease of synthesis of the developed functional nanocomposites make them suitable for large-scale applications, especially in the fields of medical, sensing, and environmental monitoring. For the medical application, it is shown that synthesized nanocomposites can strongly inhibit the growth of Escherichia coli and Staphylococcus aureus. Furthermore, the particles also exhibit very good antifungal and antiviral activity.
Biosynthesis of metallic-nanomaterials has emerged as a non-toxic and economical approach to their applications in diverse fields especially in biomedical sciences. Herein, this study first time reporting the use of Bombax ceiba flower extract for synthesis of selenium nanoparticles (SeNPs). Initially, SeNPs were confirmed by turning the color of reaction mixtures from light yellow to red-brick. Scanning electron microscope (SEM) and Transmission electron microscopy (TEM) images showed spherical shaped nanoparticles with smooth surface, size ranges between 30–150 nm. Dynamic light scattering (DLS) showed 100–150 nm for the distribution of particle size. X-ray diffraction (XRD) analysis revealed SeNPs crystallinity and confirmed by matching with selenium JCPD card No. 06-362. Energy-dispersive X-ray (EDX) spectra showed presence of pure Se peaks that corroborate the conversion of selenium ions into its elemental form by bio-reduction. Fourier-transform infrared spectroscopy (FTIR) spectra demonstrated that involvement of -OH, C-H, C = C, and C = O functional groups for SeNPs formation. Raman Spectra peaks at 250 cm− 1 represent asymmetric trigonal selenium (t-Se). Ultraviolet-visible spectrophotometer (UV-Vis) peaks at 296 and 306 nm which is an indication of surface plasmon resonance (SPR). Moreover, maximum antibacterial activity of SeNPs were observed against Staphylococcus aureus- a gram positive bacteria that possess zone of inhibition (ZOI) 20 mm and Klebsiella pneumonia and Pseudomonas aeruginosa-gram negative bacterias with ZOI 28 mm, respectively, at concentration 100 µg/ ml. In addition, the surface functionalities induced through extract components adhere over Se binds with urea and give its detection up to 1mM in milk sample. Conclusively, synthesized SeNPs may act as a potent potential antibacterial pharmaceutical candidate.
Recently, graphene quantum dots (GQDs), zero-dimensional flat nanomaterials with distinct optical, electrical, and optoelectric properties, have attracted significant attention, owing to their non-toxicity and physiological inertness. A variety of top-down and bottom-up methodologies have been exploited for the synthesis of these materials, including electrochemical oxidation, hydrothermal or solvothermal, microwave-assisted, controllable synthesis and carbonization from organic molecules or polymers. This review focuses on the synthesis and applications of GQDs in solar cells, supercapacitors, LEDs, and Li/Na ion batteries. Herein, we summarized in detail the synthesis methods for GQDs employed in energy storage applications with enhanced capacitance, power conversion, retention capability, and stability, achieved by adjusting many synthesis parameters, including annealing temperature, growth time, substrate concentration, and catalyst. The conclusion highlights the potential opportunities and challenges related to future research on GQDs.
Green packaging wrap is now required to replace the synthetic plastic coating on the paper substrates. The coating of natural biopolymers on the paper substrates would be a potential method to achieve an ecofriendly coating to replace the synthetic materials which give a threat to the environment. Recently, spraying cellulose nanofiber (CNF) on the paper substrates to boost the barrier and mechanical properties of the paper is a flexible process and potential for scalability. Sprayed cellulose nanofibrils fill the surface pores of the paper substrates and form a barrier film on the paper surface. The spray-coated CNF barrier film on the paper substrates reduced the air passage and increased the mechanical strength. To scale up the process of spraying, the optimization was performed via response surface methodology to investigate the interaction between input variables and their response in spraying process. The variables impacting on the barrier performance, CNF coat weight, and thickness of the coat during spraying are CNF suspension concentration (
A
), fiber diameter (
B
), and spray distance from tip to the surface (
C
). The linear models were developed for CNF coat weight and thickness of the CNF coat weight on the paper substrates. The quadratic model for air permeability was developed with input variables. It concludes that the CNF suspension concentration is a strong parameter for controlling the CNF coat weight and thickness of the CNF coat on the paper substrates. The developed linear and quadratic models were validated with the experimental data confirming that it was a good fit to the real experimental data. From the CCD investigation of spray coating of CNF on the paper substrates, >1 wt.% CNF coating on the paper surface produces good thickness and coat weight on the paper substrates and gives an impermeable CNF laminate on the paper substrates against air. In conclusion, these models could provide a platform for scaling up the spraying process for coating CNF-based nanomaterials on the paper substrates.
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