A Fluorescence/Colorimetric Synergistic-Enhanced Type-I Heterostructured MOF@QDs for Both Multi-Depth Food-Freshness Prediction and Extra Preservation.

The aim of this research was to prepare a different particle sizes of zinc oxide nanostructures by two different methods. The zinc oxide nanoparticle (ZnO NPs) was successfully prepared by a green synthesis technique but the zinc oxide quantum dot (ZnO QDs) was successfully prepared by a chemical method. The structure, composition and morphology of the prepared different shapes of ZnO nanostructures have been characterized by the means of X-ray diffractograms (XRD), high resolution transmission electron microscope (HRTEM), Energy Dispersive x-ray (EDX), UV-Vis spectroscopy and Fourier transform infrared spectroscopy (FTIR). From UV-Vis spectroscopy studies we noticed that the optical band gap energy of ZnO nanostructures was decreased by increasing an irradiation time. The removal of complex organic contaminants and pollutants from water, the heterogeneous photocatalytic degradation of methylene blue (MB), Fluorescein and Rhodamine 6G (Rh 6G) dyes were studied using ZnO NPs and ZnO QDs as a derived catalyst. We had studied the impact of ZnO NPs and ZnO QDs as a catalyst to enhance the photocatalytic activity of different organic dyes under UV-Vis irradiation and we observed that the photodegradation percentage of organic dyes was rapidly increased by increasing UV irradiation time in both two shapes of ZnO nanostructures. ZnO QDs behave as the best photocatalyst for successfully photodegraded due to the smallest size of ZnO QDs has a higher photocatalytic activity than the large particle size of ZnO NPs. So, it is better to use the ZnO QDs as a removal dyes and pollutants in the wastewater application. Also, we have assessed the cytotoxicity of ZnO NPs and ZnO QDs against two cell lines, (T-47) breast cancer carcinoma, and (DU-145) prostate cancer cell compared to Human skin fibroblast (HSF). The proliferation of cancer cells using MTT assay clarified that both cancer cells (T-47), (DU-145) as well as (HSF) normal cell line are regularly inhibited as they grow on different concentrations of ZnQ QDs and ZnQ NPs. The maximum inhibitory effect of both were recorded at concentration of 100 µg/ml (62.63, 79.72 and 42.59% and 72.68, 83.28, 18.12 µg/ml) in case of ZnQ QDs and ZnQ NPs respectively. It was cleared that ZnQ NPs was more potent for test cancer cell lines, this was confirmed by IC50, since it was (18.12,13.3,74.86) in ZnO NPs compared with (42.59,17.05 and 76.4) in ZnQ QDs respectively. Finally, it was proved that the ZnO NPs behave as a good anticancer nanomaterial than ZnO QDs. This means ZnO NPs are superior for anticancer applications if compared with ZnO QDs.

Polymeric membranescomposed of poly­(3-hydroxybutyrate) (PHB) integratedwith zinc oxide nanoparticles (ZnO NPs) or quantum dots (ZnO QDs)were successfully prepared by using a sol–gel method for nanostructuredispersion. The resulting PHB/ZnO membranes exhibited uniform morphologyand fluorescence with well-dispersed nanostructures confirmed by UV–visspectrophotometry, fluorescence analysis, and FTIR spectroscopy. Spectralanalysis revealed that ZnO NPs and QDs enhanced UV-blocking capabilitiesand reduced the level of membrane yellowing. Physicochemical evaluationsshowed that the fluorescence remained stable under prolonged watervapor exposure. Increasing the ZnO content (5, 10, and 15%) led tohigher membrane density, wettability, and hardness. Swelling and watervapor permeability (WVP) tests indicated that ZnO QDs were the mosteffective in reducing moisture diffusion, suggesting the formationof internal barriers. Despite increased surface hydrophilicity, WVPdecreased, highlighting the dual functionality of the nanostructures.Antibacterial assays demonstrated inhibition of Staphylococcusaureus growth by up to 30.08% (ZnO NPs) and 21.83%(ZnO QDs). These findings support the potential of PHB/ZnO membranesas multifunctional materials for advanced packaging applications,offering tailored UV protection, moisture control, and antimicrobialproperties suitable for the food, pharmaceutical, and cosmetic industries.

Physiological responses of pumpkin to zinc oxide quantum dots and nanoparticles

Candidiasis caused by Candida albicans is one of the most common microbial infections. Azoles, polyenes, allylamines, and echinocandins are classes of antifungals used for treating Candida infections. Standard drug doses often become ineffective due to the emergence of multidrug resistance (MDR). This leads to the use of higher drug doses for prolonged duration, resulting in severe toxicity (nephrotoxicity and liver damage) in humans. However, combination therapy using very low concentrations of two or more antifungal agents together, can lower such toxicity and limit evolution of drug resistance. Herein, 4–6 nm zinc oxide quantum dots (ZnO QDs) were synthesized and their in vitro antifungal activities were assessed against drug-susceptible (G1, F1, and GU4) and resistant (G5, F5, and GU5) isolates of C. albicans. In broth microdilution assay, ZnO QDs exhibited dose dependent growth inhibition between 0 – 200 µg/ml and almost 90% growth was inhibited in all Candida strains at 200 µg/ml of ZnO QDs. Synergy between ZnO QDs and antifungal drugs at sub-inhibitory concentrations of each was assessed by checkerboard analysis and expressed in terms of the fractional inhibitory concentration (FIC) index. ZnO QDs were used with two different classes of antifungals (azoles and polyenes) against Candida isolates: combination 1 (with fluconazole); combination 2 (with ketoconazole); combination 3 (with amphotericin B), and combination 4 (with nystatin). Results demonstrated that the potency of combinations of ZnO QDs with antifungal drugs even at very low concentrations of each was higher than their individual activities against the fungal isolates. The FIC index was found to be less than 0.5 for all combinations in the checkerboard assay, which confirmed synergism between sub-inhibitory concentrations of ZnO QDs (25 µg/ml) and individual antifungal drugs. Synergism was further confirmed by spot assay where cell viabilities of Candida strains were significantly reduced in all combinations, which was clearly evident from the disappearance of fungal cells on agar plates containing antifungal combinations. For safer clinical use, the in vitro cytotoxic activity of ZnO QDs was assessed against HeLa cell line and it was found that ZnO QDs were non-toxic at 25 µg/ml. Results suggested that the combination of ZnO QDs with drugs potentiate antimicrobial activity through multitargeted action. ZnO QDs could therefore offer a versatile alternative in combination therapy against MDR fungal pathogens, wherein lowering drug concentrations could reduce toxicity and their multitargeted action could limit evolution of fungal drug resistance.

A green strategy and cost-effective approach was adapted to prepare Zinc oxide quantum dots (ZnO QDs) for biomedical applications. The prepared ZnO QDs may hold great promise as sensing scanners for diagnostics and therapy, as demonstrated in our current study. Zinc sulfate, Azadirachta indica, Aloe vera gel and Catharanthus roseus leaves extract were used to synthesize a novel natural Zinc oxide bionanocomposite (ZnO BC) and used as a precursor to prepare ZnO QDs by microwave-assisted technique. The ZnO BC was characterized by SEM–EDX, FT-IR, XRD, Zeta potential, and particle size analysis. The optical properties of QDs were investigated using UV and PL spectrophotometers. Experimental factors like the concentrations of ZnO Nps, C. roseus, and Aloe vera were evaluated using Box–Behnken design (BBD). MTT and hemolysis assay was performed using ZnO BC and ZnO QDs. Maximum absorbance was observed at optimized values of 0.5% ZnO Nps, 1 g A. vera gel, and 0.5 ml C. roseus leaf extract of ZnO QDs against BBD. There was a decreased viability rate, ranging from 60 to 15% for 0.5 mg/ml ZnO BC and 45 to 5% for 5 mg/ml ZnO QDs which revealed a tenfold decrease in cell viability with less concentration scale for 5 mg/ml of ZnO QDs when compared with that of 0.5 mg/ml ZnO BC. Also, the hemolysis test shows that the hemolysis ratio was below 0.5%, indicating non-hemolysis of ZnO QDs. Cellular morphology by results was supported by phase-contrast microscopy images. Good biocompatibility and high anticancer activity were noticed for ZnO QDs when compared to ZnO BC and provide versatile applications in the field of nano-biomedicine.Graphical abstract

Novel zinc oxide quantum dots (ZnO QDs) decorated graphene nanocomposites were fabricated by a facile solution-processed method. ZnO QDs with a size ca. 5 nm are nucleated and grown on the surface of the graphene template, and its distribution density can be easily controlled by the reaction time and precursor concentration. The ZnO QDs/graphene nanocomposite materials enhance formaldehyde sensing properties by 4 times compared to pure graphene at room temperature. Moreover, the sensors based on the nanocomposites have fast response (ca. 30 seconds) and recovery (ca. 40 seconds) behavior, excellent room temperature selectivity and stability. The gas sensing enhancement is attributed to the synergistic effect of graphene and ZnO QDs. The electron transfer between the ZnO QDs and the graphene is due to oxidation process of the analyzed gas on the ZnO QDs' surface. This proposed gas sensing mechanism is experimentally proved by DRIFT spectra results. The ZnO QDs/graphene nanocomposites sensors have potential applications for monitoring air pollution, especially for harmful and toxic VOCs (volatile organic compounds).

Zinc oxide quantum dots, also known as ZnO QDs, are highly desirable due to their numerous favorable characteristics, such as their beneficial photoluminescence, solubility in water, along with sunlight absorption. They are well-suited for use in biomedical applications, drugs, and bioimaging. However, study on the in-vivo toxicology of these QDs is needed before they can be used in humans. Zebrafish (Danio rerio) are cheap, fast-growing, and similar to humans, which makes them ideal as in vivo model for studying the toxicity of nanomaterials. The toxicity investigations involving zinc oxide QDs (ZnO QDs) and zinc oxide bionanocomposite (ZnO BC) in zebrafish that were concentration-dependent are evaluated, and the Box-Behnken design (BBD) was utilized to optimize the results. To determine the proper dosage, a study on cell line as well as hemocompatibility was carried out prior to testing the toxic effects of ZnO QDs along with ZnO BC upon zebrafish. When administered at 2.5 μg/l of ZnO BC and 2 μg/l of ZnO QDs, neither ZnO BC nor ZnO QDs appeared to be toxic to embryos during hatching and development. The testing of larval behavior in visible light revealed a dose-dependent decrease in both the total diving distance as well as speed. Nevertheless, at ZnO BC and ZnO QDs levels >250 μg/l and >200 μg/l, respectively, notable effects were seen in zebrafish embryos. Hence, ZnO QDs and BC at low concentrations were notably nontoxic. In order to guarantee the safety of nanomaterials in bio applications, this research supports upcoming in-vivo imaging investigations on their harmful effects.

Streptococcus agalactiae is a significant pathogen that can affect both human beings and animals. The extensive current use of antibiotics has resulted in antibiotic resistance. In our previous research, we found that zinc oxide quantum dots (ZnO QDs) had inhibitory effects on antibiotic-resistant microorganisms. In this study, a strain of Streptococcus agalactiaeWJYT1 with a broad antibiotic-resistant spectrum was isolated and identified from Lama glama at Sichuan Agricultural University Teaching Animal Hospital. The genome for the resistance and virulence genes was analyzed. Additionally, the antibacterial effects and anti-virulence mechanism of ZnO QDs for S. agalactiaeWJYT1 were investigated. The results showed that the genome of S. agalactiaeWJYT1 is 1,943,955 bp, containing 22 resistance genes and 95 virulence genes. ZnO QDs have a good antibacterial effect against S. agalactiaeWJYT1 by reducing bacterial growth and decreasing the expression of virulence genes, including bibA, hylB, sip, and cip, which provides a novel potential treatment for S. agalactiae.

Zinc oxide quantum dots (ZnO QDs) were synthesized by gel-sol method and employed as the transdermal aloesin (Alo) carriers. ZnO QDs were surface-functionalized with amino using aminopropyltriethoxysilane (APTES). Alo was covalently bonded on the surface of ZnO QDs via N,N'-carbonyldiimidazole to obtain Alo NPs, which were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analyzer (TGA). TEM images showed that ZnO QDs were analogously sphere and monodisperse with a reasonably narrow size distribution, of which was around 4 nm. The size of Alo NPs increased to around 8 nm due to the surface modification. The intense bands at around 3 400 cm -1 and 1 200 cm -1 in the FTIR spectrum of Alo NPs from the vibration of -OH indicated the linkage of Alo on the surface of ZnO QDs. The results of TGA analysis showed that the mass ratio of ZnO QDs and Alo were 39.27% and 35.14%, respectively. The penetration of Alo NPs was much higher than raw Alo according to the passive penetration experiments with Franz-type diffusion cells instrument using full-thickness cavy skin, which manifested the improvement of the penetration for Alo delivered by ZnO QDs. The pH-controlled drug release behavior in vitro was investigated. At pH 7.4, only a small amount of Alo (1.45% ± 0.21%) had been released after 2 h. In contrast, as incubation at pH 5.0 of which pH was similar to endosomal environment, Alo was released very fast (87.63% ± 0.46% in 2 h) from Alo NPs, confirming that Alo NPs could response to the pH and realize the intracellular drug release. The inhibitory effect of Alo NPs on tyrosinase was in a dose dependent manner. When the concentration of Alo NPs was 12.5 μg/mL, the inhibition rate was up to 40.32% ± 1.57%. All the results show that the Alo NPs hold a great potential in transdermal tyrosinase inhibition.

This research focuses on the synthesis of ZnO quantum dots with a cationic polymer coating consisting of poly[2‐(methacryloyloxy)ethyl]‐ammonium chloride–co‐poly(poly‐ethyleneglycol methyl methacrylate (p(METAC‐PEOMEMA)) for Fe 2+ detection. The copolymers of p(METAC‐PEOMEMA) at various molar ratios of METAC/PEOMEMA (100/0, 38/62, and 9/91) were synthesized by RAFT polymerization. The p(METAC‐PEOMEMA) capped trisodium citrate‐ZnO quantum dot (p(METAC‐PEOMEMA)‐ZnO QDs) were prepared via ionic interaction of trisodium citrate‐ZnO QDs and p(METAC‐PEOMEMA). The optical properties of the polymer‐capped ZnO QDs were studied by UV‐Vis and fluororescence spectrophotometry. The p(METAC‐PEOMEMA)‐ZnO QDs exhibited excellent properties such as high monodispersity in particle sizes, good stability, excellent water dispersibility, and good quantum yield of 27–32%. The p(METAC 9 ‐PEOMEMA 91 )‐ZnO QDs is quenched by Fe 2+ with a good selectivity over other metal ions such as Fe 3+ , Hg 2+ , Co 2+ , Pb 2+ , Cd 2+ , Ni 2+ , Ag + , Cu 2+ , and Na + . A good linear relationship between relative fluorescence intensity and the concentration of Fe 2+ ion was observed over an Fe 2+ concentration range from 0.47 μM to 5.6 μM, with a limit of detection and limit of quantitation at 0.34 μM and 0.51 μM, respectively. Its application for the detection of Fe 2+ ion in drinking water samples was demonstrated.

Fluorescent anti-counterfeiting is one of the most widely used anti-counterfeiting technologies at present. The demand to develop new anti-counterfeiting materials and technology is more and more urgent. Zinc oxide quantum dots (ZnO QDs) have superior fluorescent properties under ultraviolet light, making them a suitable replacement for traditional phosphors for anti-counterfeiting printing, which is environmentally friendly and meets the needs of sustainable development. In this paper, water-soluble ZnO QDs with an average particle size of 5.64 nm were prepared. Paper coated by ZnO QDs was obtained after ultrasonic treatment, which could emit bright yellow fluorescence when excited by ultraviolet light. As the concentration of ultrasonic solution is increased, the loading amount of ZnO QDs on the coated paper increased gradually, reaching the maximum when the concentration is increased to 1molL-1, which then does not change with an increase in concentration. The fluorescent intensity of the coated paper was consistent with the changing trend of the loading amount. The coated paper has excellent optical stability, is easy to recycle, and provides simple identification of authenticity by ultraviolet light and anti-copy functionality. Their application in packaging and printing is of great significance to the development of complex, concealed and non-repeatable anti-counterfeiting technology.

A graphene oxide amplification platform tagged with tyrosinase–zinc oxide quantum dot hybrids for the electrochemical sensing of hydroxylated polychlorobiphenyls

BACKGROUNDOrganic dyes are extremely hazardous waste toxins because they can harm all living organisms as well as the environment. Among them, azo dyes are the most harmful, containing a non‐degradable azo group (NN); these dyes are highly hazardous for both humans and animals, even in low concentration. This research study aims to remove hazardous anionic azo dyes from aqueous solutions by a simple adsorption method using zinc oxide quantum dots (ZnO QDs) synthesized by a facile precipitation method.RESULTSAs synthesized, ZnO QDs were characterized by transmittance electron microscopy, atomic force microscopy, X‐ray powder diffraction, Fourier transform infrared spectroscopy, zeta potential and Brunauer–Emmett–Teller. The azo dyes Methyl Orange (MO), Congo Red (CR) and Eriochrome Black‐T (EBT) have been removed actively from an aqueous solution using the high adsorption characteristic of ZnO QDs. The results demonstrated that the adsorbent was efficient even at a low concentration at 0.05 g L−1. The maximum adsorption capacity of ZnO QDs at 27 ± 1 °C was 102.9, 124.3 and 60 mg L−1 for MO, CR and EBT, respectively, and all these results have been observed in just 30 min. A pseudo‐second‐order and Langmuir isotherm model satisfactorily suited the dye adsorption data and, up to three cycles, the ZnO QDs demonstrated outstanding reusability.CONCLUSIONZnO QDs showed not only efficient removal of individual dyes but also simultaneous removal of azo dyes from mixture solution and proved to be an effective, eco‐friendly, low‐cost adsorbent for dye decontamination in wastewater. © 2022 Society of Chemical Industry (SCI).

Bacterial fruit blotch is one of the most destructing diseases of melon producing-regions. Here, zinc oxide quantum dots (ZnO QDs) were synthesized, and their antibacterial activity against Acidovorax citrulli was investigated. The results indicated that the obtained ZnO QDs displayed 5.7-fold higher antibacterial activity than a commercial Zn-based bactericide (zinc thiazole). Interestingly, the antibacterial activity of ZnO QDs irradiated with light was 1.8 times higher than that of the dark-treated group. It was because ZnO QDs could induce the generation of hydroxyl radicals and then up-regulate the expression of oxidative stress-related genes, finally leading to the loss of cell membrane integrity. A pot experiment demonstrated that foliar application of ZnO QDs significantly reduced the bacterial fruit blotch disease incidence (32.0%). Furthermore, the supply of ZnO QDs could improve the growth of infected melon seedlings by activating the antioxidant defense system. This work provides a promising light-activated quantum-bactericide for the management of pathogenic bacterial infections in melon crop protection.

Zinc oxide quantum dot (ZnO QD)/gold nanoparticle (Au NP) nanocomposites with Janus structure were synthesized through a bridge linking of 3-mercaptopropionic acid (3MPA). The bare ZnO QDs presented a typically weak inherent ultraviolet (UV) emission band and a strong defect-related visible band. After Au NPs were assembled onto the surfaces of ZnO QDs, the ZnO/Au nanocomposites exhibited a dramatic enhancement of UV emission and quenching of visible emission. It was noted that the defect emission of ZnO QDs matched with the localized surface plasmon resonance (LSPR) peak of Au NPs, which resulted in a LSPR-assisted electron transfer process from Au NPs to ZnO QDs, so the defect emission was suppressed. The LSPR-assisted electron transfer process was confirmed by the time-resolved photoluminescence.