The effect of mechanical stirring on sol-gel synthesis of thorn-like ZnO nanoparticles (ZnO-NPs) and antimicrobial activities is successfully reported in this study. The in-house synthesized nanoparticles were characterized by XRD, SEM, TEM, FTIR, TGA, DSC and UV-visible spectroscopy. The X-Ray Diffraction analysis revealed the wurtzite crystal lattice for ZnO-NPs with no impurities present. The diametric measurements of the synthesized thorn-like ZnO-NPs (morphology assessed by SEM) were well accounted to be less than 50 nm with the help of TEM. Relative decrease in aspect ratio was observed on increasing the agitation speed. The UV-visible spectroscopy showed the absorption peaks of the ZnO-NPs existed in both UVA and UVB region. A hypsochromic shift in λmax was observed when stirring pace was increased from 500 rpm to 2000 rpm. The FTIR spectroscopy showed the absorption bands of the stretching modes of Zn-O between 500 cm−1 to 525 cm−1. The Thermal analysis studies revealed better stability for ZnO-NPs prepared at 2000 rpm (ZnO-2000 rpm). TGA revealed the weight loss between two main temperatures ranges viz. around (90 °C–120 °C) and (240 °C–280 °C). Finally, the effect of ZnO-NPs prepared at different stirring conditions on the growth of Gram-positive (Bacillus subtilis), Gram-negative (Escherichia coli) bacteria and a fungi (Candida albicans) were examined; which showed good antibacterial as well as antifungal properties. These findings introduce a simple, inexpensive process to synthesize ZnO-NPs using conventional methods without the use of sophisticated equipments and its application as a potent nano-antibiotic.
Due to enormous applications of metal oxide nanoparticles in research and health-related applications, metal oxide nanoparticles are increasingly being developed through cheaper and more user-friendly approaches. We have formulated a simple route to synthesize zinc oxide nanoparticles (ZNPs) by a sol–gel method at near-room temperatures 25°C, 35°C, 55°C, and 75°C. The results are analyzed by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and ultraviolet-visible absorption spectroscopy. The effect of different temperature conditions (25°C–75°C) on the particulate sizes (23.7–88.8 nm), pH levels (11.7–11.9), and morphologies (slender needle–broad arrow) of flower-shaped ZNP colonies is studied. A possible mechanism depicting the growth rates at different temperatures and of different facets, mainly towards the <0 0 0 I> and <0 I Ī 0> planes of the ZNPs has also been discussed. The values of λ
max
(293–298 nm) suggest that ZNPs prepared at 55°C are the most effective ultraviolet B absorbers, and that they can be used in sunscreens. Highly significant antimicrobial activity against medically important Gram-positive (
Staphylococcus aureus
) and Gram-negative (
Escherichia coli
) bacteria and fungi (
Candida albicans
) by these ZNPs was also revealed. As
S. aureus
and
C. albicans
are responsible for many contagious dermal infections such as abscesses, furuncles, carbuncles, cellulitis, and candidiasis, we can postulate that our fabricated ZNPs may be useful as antimicrobial agents in antiseptic creams and lotions for the treatment of skin diseases.
This study evaluates the impact of
two separate incubation periods
(4 and 6 weeks) on the morphology of sol–gel-fabricated ZnO
nanospikes (ZNs), that is, ZN1 and ZN2, respectively. We further analyzed
the inhibitory effects of ZN1 and ZN2 on quorum sensing (QS) and biofilm
formation in
Pseudomonas aeruginosa
(PAO1) and
Chromobacterium violaceum
(strains 12472 and CVO26). The size of the synthesized ZNs was in
the range of 40–130 nm, and finer nanoparticles were synthesized
after an incubation period of 6 weeks. Treatment with ZNs decreased
the production of violacein in the pathogen without affecting the
bacterial growth, which indicated that ZNs inhibited the QS signaling
regulated by
N
-acyl homoserine lactone. ZN2 had a
higher inhibitory action on the virulence factor productivity than
ZN1. Furthermore, ZN2-treated cells displayed a substantial decrease
in azocasein-degrading protease activity (80%), elastase activity
(83%), and pyocyanin production (85%) relative to untreated
P. aeruginosa
PAO1 cells. Treatment with ZN2 decreased
swarming motility and exopolysaccharide production by 89 and 85%,
respectively. ZN2 was effective against both the
las
&
pqs
systems of
P. aeruginosa
and exhibited broad-spectrum activity. Additionally, ZN2 was more
efficient in inhibiting the biofilm formation at the attachment stage
than ZN1. These findings revealed that in
P. aeruginosa
, ZN2 demonstrated inhibitory effects on QS as well as on the development
of biofilms. Thus, ZN2 can be potentially used to treat drug-resistant
P. aeruginosa
infections.
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