Modulation of defect-mediated energy transfer from ZnO nanoparticles for the photocatalytic degradation of bilirubin

Ag nanoparticles on ZnO nanoplates as a hybrid SERS-active substrate for trace detection of methylene blue

Decorating two-dimensional (2D) nanomaterials with nanoparticles provides an effective method to integrate their physicochemical properties. In this work, we present the hydrothermal growth process of 2D zinc oxide nanoplates (ZnO NPls), then silver nanoparticles (AgNPs) were uniformly distributed on the surface of ZnO NPls through the reduction procedure of silver nitrate with sodium borohydride to create a metal–semiconductor hybrid. The amount of AgNPs on the ZnO NPls' surface was carefully controlled by varying the volume of silver nitrate (AgNO₃) solution. Moreover, the effect of AgNPs on the surface-enhanced Raman scattering (SERS) property of ZnO NPls was thoroughly investigated by using methylene blue (MB) as the target molecule. After calculation, the maximum enhancement factor value for 10⁻⁴ M of MB reached 6.2 × 10⁶ for the peak at 1436 cm⁻¹ and the limit of detection was 10⁻⁹ M. In addition, the hybrid nanosystem could distinguish MB with good reproducibility over a wide range of concentrations, from 10⁻⁹ to 10⁻⁴ M. The SERS mechanism is well elucidated based on the chemical and electromagnetic mechanisms related to the synergism of ZnO and Ag in the enhancement of Raman signal. Abundant hot spots located at the gap between adjacent separate Ag nanoparticles and ZnO nanoplates which formed a strong local electromagnetic field and electron transfer between ZnO and Ag are considered to be the key factors affecting the SERS performance of our prepared ZnO/Ag substrates. In this research, we found high sensitivity of ZnO nanoplates/Ag nanoparticles in detecting MB molecules. This unique metal–semiconductor hybrid nanosystem is advantageous for the formation of Raman signals and is thus suitable for the trace detection of methylene blue.

Decorating two-dimensional (2D) nanomaterials with nanoparticles provides an effective method to integrate their physicochemical properties.

Nanoceutical Fabric Prevents COVID-19 Spread through Expelled Respiratory Droplets: A Combined Computational, Spectroscopic, and Antimicrobial Study

Centers for Disease Control and Prevention (CDC) warns the use of one-way valves or vents in face masks for potential threat of spreading COVID-19 through expelled respiratory droplets. Here, we have developed a nanoceutical cotton fabric duly sensitized with non-toxic zinc oxide nanomaterial for potential use as a membrane filter in the one-way valve for the ease of breathing without the threat of COVID-19 spreading. A detailed computational study revealed that zinc oxide nanoflowers (ZnO NFs) with almost two-dimensional petals trap SARS-CoV-2 spike proteins, responsible to attach to ACE-2 receptors in human lung epithelial cells. The study also confirmed significant denaturation of the spike proteins on the ZnO surface, revealing removal of the virus upon efficient trapping. Following the computational study, we have synthesized ZnO NF on a cotton matrix using a hydrothermal-assisted strategy. Electron-microscopic, steady-state, and picosecond-resolved spectroscopic studies confirm attachment of ZnO NF to the cotton (i.e., cellulose) matrix at the atomic level to develop the nanoceutical fabric. A detailed antimicrobial assay using Pseudomonas aeruginosa bacteria (model SARS-CoV-2 mimic) reveals excellent antimicrobial efficiency of the developed nanoceutical fabric. To our understanding, the nanoceutical fabric used in the one-way valve of a face mask would be the choice to assure breathing comfort along with source control of COVID-19 infection. The developed nanosensitized cloth can also be used as an antibacterial/anti CoV-2 washable dress material in general.

Nanoceutical Fabric Prevents COVID-19 Spread through Expelled Respiratory Droplets: A Combined Computational, Spectroscopic, and Antimicrobial Study

Centers for Disease Control and Prevention (CDC) warns the use of one-way valves or vents in face masks for potential threat of spreading COVID-19 through expelled respiratory droplets. Here, we have developed a nanoceutical cotton fabric duly sensitized with non-toxic zinc oxide nanomaterial for potential use as a membrane filter in the one-way valve for the ease of breathing without the threat of COVID-19 spreading. A detailed computational study revealed that zinc oxide nanoflowers (ZnO NFs) with almost two-dimensional petals trap SARS-CoV-2 spike proteins, responsible to attach to ACE-2 receptors in human lung epithelial cells. The study also confirmed significant denaturation of the spike proteins on the ZnO surface, revealing removal of the virus upon efficient trapping. Following the computational study, we have synthesized ZnO NF on a cotton matrix using a hydrothermal-assisted strategy. Electron-microscopic, steady-state, and picosecond-resolved spectroscopic studies confirm attachment of ZnO NF to the cotton (i.e., cellulose) matrix at the atomic level to develop the nanoceutical fabric. A detailed antimicrobial assay using Pseudomonas aeruginosa bacteria (model SARS-CoV-2 mimic) reveals excellent antimicrobial efficiency of the developed nanoceutical fabric. To our understanding, the nanoceutical fabric used in the one-way valve of a face mask would be the choice to assure breathing comfort along with source control of COVID-19 infection. The developed nanosensitized cloth can also be used as an antibacterial/anti CoV-2 washable dress material in general.

Optimization of zinc oxide nanoparticle-catalyzed in vitro bilirubin photolysis and in vivo treatment of hyperbilirubinemia

Aim: To optimize the Zinc oxide nanoparticles (ZnONPs)-catalyzed in vitro photolysis of bilirubin and to test their effect on bilirubin clearance in vivo. Materials & methods: ZnONPs, synthesized in an alkaline medium, were characterized. Response surface methodology was used to optimize the in vitro photolysis catalyzed by the nanoparticles (NPs). Blood samples from phenylhydrazine-induced hyperbilirubinemic rabbits which had been administered ZnONPs and UV light were analyzed to assess in vivo clearance of bilirubin. Results: The ZnONP-assisted UV treatment showed the linear and quadratic positive effects on the in vitro bilirubin photolysis with an optimal photolysis of bilirubin at 225 mg dl^-1 concentration of ZnONPs and a UV exposure of 1.80 h. The ZnONP-assisted phototherapy of hyperbilirubinemic animals was also found to be more effective for in vivo clearance of bilirubin than phototherapy alone. Conclusion: After further trials, ZnONP-assisted phototherapy could be a potential treatment for hyperbilirubinemia in humans.

Wide bandgap semiconductor-based novel nanohybrid for potential antibacterial activity: ultrafast spectroscopy and computational studies

The properties of nanomaterials generated by external stimuli are considered an innovative and promising replacement for the annihilation of bacterial infectious diseases.

Ultrafast dynamics in co-sensitized photocatalysts under visible and NIR light irradiation

Activity modulation of co-sensitized light harvesting nanohybrids by tuning the ultrafast carrier dynamics under visible and NIR light irradiation.

The role of l-cysteine and introduced surface defects in reactive oxygen species generation by ZnO nanoparticles

The synthesis and surface functionalization of ZnO nanoparticles were performed, with attention being paid to the possible bio-related applications in light-triggered reactive oxygen species generation.

Influence of Atomic Hydrogen, Band Bending, and Defects in the Top Few Nanometers of Hydrothermally Prepared Zinc Oxide Nanorods

We report on the surface, sub-surface (top few nanometers) and bulk properties of hydrothermally grown zinc oxide (ZnO) nanorods (NRs) prior to and after hydrogen treatment. Upon treating with atomic hydrogen (H*), upward and downward band bending is observed depending on the availability of molecular H₂O within the structure of the NRs. In the absence of H₂O, the H* treatment demonstrated a cleaning effect of the nanorods, leading to a 0.51 eV upward band bending. In addition, enhancement in the intensity of room temperature photoluminescence (PL) signals due to the creation of new surface defects could be observed. The defects enhanced the visible light activity of the ZnO NRs which were subsequently used to photocatalytically degrade aqueous phenol under simulated sunlight. On the contrary, in the presence of H₂O, H* treatment created an electronic accumulation layer inducing downward band bending of 0.45 eV (~1/7th of the bulk ZnO band gap) along with the weakening of the defect signals as observed from room temperature photoluminescence spectra. The results suggest a plausible way of tailoring the band bending and defects of the ZnO NRs through control of H₂O/H* species.

Zinc Oxide Nanoparticle-Poly I:C RNA Complexes: Implication as Therapeutics against Experimental Melanoma

There is current interest in harnessing the combined anticancer and immunological effect of nanoparticles (NPs) and RNA. Here, we evaluate the bioactivity of poly I:C (pIC) RNA, bound to anticancer zinc oxide NP (ZnO-NP) against melanoma. Direct RNA association to unfunctionalized ZnO-NP is shown by observing change in size, zeta potential, and absorption/fluorescence spectra upon complexation. RNA corona was visualized by transmission electron microscopy (TEM) for the first time. Binding constant (K_b = 1.6-2.8 g^-1 L) was determined by modified Stern-Volmer, absorption, and biological surface activity index analysis. The pIC-ZnO-NP complex increased cell death for both human (A375) and mouse (B16F10) cell lines and suppressed tumor cell growth in BALB/C-B16F10 mouse melanoma model. Ex vivo tumor analysis indicated significant molecular activity such as changes in the level of phosphoproteins JNK, Akt, and inflammation markers IL-6 and IFN-γ. High throughput proteomics analysis revealed zinc oxide and poly I:C-specific and combinational patterns that suggested possible utility as an anticancer and immunotherapeutic strategy against melanoma.

Biosynthesis and characterization of MgO nanoparticles from plant extracts via induced molecular nucleation

We synthesized 18–80 nm sized MgO nanoparticles using three different leaf extracts with biophysical characteristics.

Riboflavin conjugated temperature variant ZnO nanoparticles with potential medicinal application in jaundice

Significant ameliorative efficiency of riboflavin conjugated ZnO nanoparticles against jaundice stress at molecular and cellular levels.

Enhanced Charge Separation and FRET at Heterojunctions between Semiconductor Nanoparticles and Conducting Polymer Nanofibers for Efficient Solar Light Harvesting

Energy harvesting from solar light employing nanostructured materials offer an economic way to resolve energy and environmental issues. We have developed an efficient light harvesting heterostructure based on poly(diphenylbutadiyne) (PDPB) nanofibers and ZnO nanoparticles (NPs) via a solution phase synthetic route. ZnO NPs (~20 nm) were homogeneously loaded onto the PDPB nanofibers as evident from several analytical and spectroscopic techniques. The photoinduced electron transfer from PDPB nanofibers to ZnO NPs has been confirmed by steady state and picosecond-resolved photoluminescence studies. The co-sensitization for multiple photon harvesting (with different energies) at the heterojunction has been achieved via a systematic extension of conjugation from monomeric to polymeric diphenyl butadiyne moiety in the proximity of the ZnO NPs. On the other hand, energy transfer from the surface defects of ZnO NPs (~5 nm) to PDPB nanofibers through Förster Resonance Energy Transfer (FRET) confirms the close proximity with molecular resolution. The manifestation of efficient charge separation has been realized with ~5 fold increase in photocatalytic degradation of organic pollutants in comparison to polymer nanofibers counterpart under visible light irradiation. Our results provide a novel approach for the development of nanoheterojunctions for efficient light harvesting which will be helpful in designing future solar devices.

Direct observation of key photoinduced dynamics in a potential nano-delivery vehicle of cancer drugs

The crucial photoinduced dynamics in ZnO nanoparticles (NPs) upon complexation with the cancer drug protoporphyrin IX (PP).

Defects in chemically synthesized and thermally processed ZnO nanorods: implications for active layer properties in dye-sensitized solar cells

We have carried out the effect of post annealing temperatures on the performance of solution-grown ZnO rods as photoanodes in dye-sensitized solar cells. Keeping our basic objective of exploring the effect of native defects on the performance of DSSC, we have synthesized ZnO rods having length in the range of 2-5 μm by a modified sonication-induced precipitation technique. We performed extensive characterization on the samples annealed at various temperatures and confirmed that annealing at 300 °C results in ZnO rods with minimum native defects that have been identified as doubly ionized oxygen vacancies. The electron paramagnetic resonance measurements on the samples, on the other hand, confirmed the presence of shallow donors in the low temperature annealed samples. We also carried out electrochemical impedance measurements to understand the transport properties at different interfaces in the solar cell assembly. We could conclude that solution-processed ZnO rods annealed at 300 °C are better suited for fabricating DSSC with improved efficiency (1.57%), current density (5.11 mA/cm(2)), and fill factor (45.29%). On the basis of our results, we were able to establish a close connection between the defects in the metal oxide electron transporting nano system and the DSSC performance.

A graphene/zinc oxide nanocomposite film protects dental implant surfaces against cariogenic Streptococcus mutans

Oral biofilms play a crucial role in the development of dental caries and other periodontal diseases. Streptococcus mutans is one of the primary etiological agents in dental caries. Implant systems are regularly employed to replace missing teeth. Oral biofilms accumulate on these implants and are the chief cause of dental implant failure. In the present study, the potential of graphene/zinc oxide nanocomposite (GZNC) against the cariogenic properties of Streptococcus mutans was explored and the anti-biofilm behaviour of artificial acrylic teeth surfaces coated with GZNC was examined. Acrylic teeth are a good choice for implants as they are low cost, have low density and can resist fracture. Microscopic studies and anti-biofilm assays showed a significant reduction in biofilm in the presence GZNC. GZNC was also found to be nontoxic against HEK-293 (human embryonic kidney cell line). The results indicate the potential of GZNC as an effective coating agent for dental implants by efficiently inhibiting S. mutans biofilms.