Surface Of Zinc Oxide Nanoparticles Research Articles

Non-monotonic evolution of the responses of ZnO-nanoparticle UV-sensitive devices under ambient aging

Ultraviolet (UV) sensitive devices based on spin-coated zinc-oxide nanoparticles (ZnO) were fabricated and characterised. They were subsequently stored in the ambient and dark conditions with low humidity for 56 days, during which time they were intermittently recharacterised to determine the aging effect on their sensing properties, including responsivity, sensitivity, and response and recovery times. Over the 56-day period, both the dark and illumination currents increased, causing the non-monotonic evolution of the performances of the devices – the responsivity improved by 9–18 folds, the sensitivity remained stable, and the response and recovery times deteriorated as they were 46 and 33 times longer, respectively. These changes were associated with an increase in the number of adsorbed oxygen molecules on the ZnO surface with time. This resulted in more photodesorbed oxygen molecules and thus more remaining charge carriers under illumination, which increased the photo-generated current and consequently responsivity. However, it also caused the current to rise and decay more slowly when the illumination appeared and disappeared, respectively, leading to the prolonged response and recovery times. The longer recovery times led in an increase in dark current, which, when combined with an increase in illumination current, resulted in a stable sensitivity. The trends of these sensing parameters were similar, but to varying degrees, regardless of the change in the radiation levels and ZnO layer thicknesses.

Synergistic Anticandidal Activities of Greenly Synthesized ZnO Nanomaterials with Commercial Antifungal Agents against Candidal Infections.

The high occurrence of mycological resistance to conventional antifungal agents results in significant illness and death rates among immunodeficient patients. In addition, the underprivileged therapeutic results of conventional antifungal agents, besides the potential toxicity resulting from long term therapy necessitate the fabrication of efficient antimicrobial combinations. Hence, the objective of the present investigation is to synthesize, characterize and investigate the anticandidal action of green zinc oxide nanoparticles (ZnO-NPs) formulated using Camellia sinensis leaf extract against three candidal pathogens. The eco-friendly synthesized ZnO-NPs were characterized utilizing different physicochemical methods and their anticandidal potency was tested utilizing a disk diffusion assay. In this setting, the size of the biofabricated ZnO-NPs was detected using transmission electron microscope (TEM) micrographs, recording an average particle size of 19.380 ± 2.14 nm. In addition, zeta potential analysis revealed that the ZnO-NPs surface charge was -4.72 mV. The biogenic ZnO-NPs reveal the highest anticandidal activity against the C. tropicalis strain, demonstrating relative suppressive zones measured at 35.16 ± 0.13 and 37.87 ± 0.24 mm in diameter for ZnO-NPs concentrations of 50 and 100 μg/disk, respectively. Excitingly, Candida glabrata showed a high susceptibility to the biofabricated ZnO nanomaterials at both ZnO-NPs' concentrations (50 and 100 μg/disk) compared to the control. Moreover, the biosynthesized ZnO-NPs revealed potential synergistic effectiveness with nystatin and terbinafine antifungal agents against the concerned strains. The maximum synergistic efficiency was noticed against the C. glabrata strain, demonstrating relative synergistic percentages of 23.02 and 45.9%, respectively. The biogenic ZnO-NPs revealed no hemolytic activity against human erythrocytes revealing their biosafety and hemocompatibility. Finally, the high anticandidal effectiveness of biogenic ZnO-NPs against the concerned candidal pathogens, as well as potential synergistic patterns with conventional antifungal agents such as nystatin and terbinafine, emphasize the prospective application of these combinations for the fabrication of biocompatible and highly efficient antifungal agents.

Adsorptive removal of pharmaceutically active compounds from multicomponent system using Azadirachta indica induced zinc oxide nanoparticles: analysis of competitive and cooperative adsorption.

In this research, zinc oxide (ZnO) nanoparticles synthesized using neem leaf (Azadirachta indica) extract were used as an adsorbent for removing two widely used pharmaceutical compounds acetaminophen (AMP) and sulfadiazine (SDZ). The synthesized ZnO nanoparticles were characterized using SEM-EDS, FTIR, TEM, BET, and XRD analysis. The synthesized ZnO nanoparticles were found to be in the size range of 10 nm with a surface area of 48.551 m2/g. The adsorptive performance of ZnO nanoparticles in both mono-component (MoS) and multi-component system (MuS) was investigated under various operational parameters viz. contact time, temperature, pH, concentration of pharmaceutical compound and ZnO nanoparticles dose. It was observed that the maximum adsorption capacity of ZnO nanoparticles was 7.87 mg/g and 7.77 mg/g for AMP and SDZ, respectively, under the optimum conditions of 7 pH and 2 g/L adsorbent dosage. The experimental data best-fitted with the pseudo-second-order model and Langmuir model, indicating monolayer chemisorption. Further investigation on removal of AMP and SDZ from multicomponent system was modelled using a Langmuir competitive model. The desorption study has shown 25.28% and 22.4% removal of AMP and SDZ from the surface of ZnO nanoparticles. In general, green synthesized ZnO nanoparticles can be utilized effectively as adsorbent for removal of pharmaceutically active compounds from wastewater.

Interactions between ZnO Nanoparticles and Polyphenols Affect Biological Responses.

Zinc oxide (ZnO) nanoparticles (NPs) are used as a food additive Zn supplement due to the role of Zn in biological functions. They are directly added to complex processed foods or Zn-fortified functional foods. Hence, the interactions between ZnO NPs and nutritional or functional components can occur. In this study, the effects of ZnO NP interactions with two polyphenols (quercetin and rutin) on cytotoxicity, antioxidant activity, ex vivo intestinal absorption, and solubility were evaluated. Moreover, the characterization on the interactions was carried out by analyzing crystallinity, surface chemical bonding, chemical composition, and surface chemistry. The results demonstrate that the interactions caused higher cytotoxicity, ex vivo intestinal transport, and solubility of ZnO NPs than pristine ZnO NPs but did not affect antioxidant activity nor intestinal absorption of the polyphenols. The interaction effects were more evident by ZnO NPs interacted with quercetin than with rutin. The crystallinity of ZnO NPs was not influenced, but the degree of exposure of the chemical bondings, elemental compositions, and chemical group intensities on the surface of ZnO NPs, quercetin, or rutin were quenched or decreased to some extent by the interactions, especially by ZnO NPs interacted with quercetin. It is, therefore, concluded that the interactions affect chemical characteristics and surface chemical sates of ZnO NPs, quercetin, or rutin, which can cause high cytotoxicity, intestinal absorption, and solubility of ZnO NPs. Further study is required to elucidate the mechanism of action of the interactions.

Zinc Oxide Nanoparticles and Their Application in Adsorption of Toxic Dye from Aqueous Solution.

Dye waste is one of the most serious types of pollution in natural water bodies, since its presence can be easily detected by the naked eye, and it is not easily biodegradable. In this study, zinc oxide nanoparticles (ZnO-NPs) were generated using a chemical reduction approach involving the zinc nitrate procedure. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and UV-vis techniques were used to analyse the surface of ZnO-NPs. The results indicate the creation of ZnO-NPs with a surface area of 95.83 m2 g−1 and a pore volume of 0.058 cm3 g−1, as well as an average pore size of 1.22 nm. In addition, the ZnO-NPs were used as an adsorbent for the removal of Ismate violet 2R (IV2R) dye from aqueous solutions under various conditions (dye concentration, pH, contact time, temperature, and adsorbent dosage) using a batch adsorption technique. Furthermore, FTIR and SEM examinations performed before and after the adsorption process indicated that the surface functionalisation and shape of the ZnO-NP nanocomposites changed significantly. A batch adsorption analysis was used to examine the extent to which operating parameters, the equilibrium isotherm, adsorption kinetics, and thermodynamics affected the results. The results of the batch technique revealed that the best results were obtained in the treatment with 0.04 g of ZnO-NP nanoparticles at 30 °C and pH 2 with an initial dye concentration of 10 mg L−1, which removed 91.5% and 65.6% of dye from synthetic and textile industry effluents, respectively. Additionally, six adsorption isotherm models were investigated by mathematical modelling and were validated for the adsorption process, and error function equations were applied to the isotherm model results in order to find the best-fit isotherm model. Likewise, the pseudo-second-order kinetic model fit well. A thermodynamic study revealed that IV2R adsorption on ZnO-NPs is a spontaneous, endothermic, and feasible sorption process. Finally, the synthesised nanocomposites prove to be excellent candidates for IV2R removal from water and real wastewater systems.

Paraclostridium benzoelyticum Bacterium-Mediated Zinc Oxide Nanoparticles and Their In Vivo Multiple Biological Applications.

We presented a low-cost, eco-friendly, and efficient bacterium-mediated synthesis of zinc oxide nanoparticles (ZnO-NPs) utilizing Paraclostridium benzoelyticum strain 5610 as a capping and reducing agent. Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray, and UV-vis spectroscopy were used to physiochemically characterize the biosynthesized ZnO-NPs. A major narrow peak at 441 nm was observed using UV-visible spectroscopy, verifying the presence of nanoparticles. According to SEM and TEM studies, the average dimensions of ZnO-NPs was 50 nm. The crystal size of 48.22 nm was determined by XRD analysis. FTIR analysis confirmed the presence of various reducing metabolites on the surface of ZnO-NPs. The synthesized nanoparticles were investigated for biological activity against Helicobacter suis, Helicobacter bizzozeronii, Helicobacter felis, and Helicobacter salomonis. Helicobacter suis was the most vulnerable strain, with an inhibitory zone of 19.53 ± 0.62 mm at 5 mg/mL dosage. The anti-inflammatory and the findings of the rat paw edema experiments revealed that the bacterium-mediated ZnO-NPs had a strong inhibitory action. In the arthritis model, the solution of ZnO-NPs showed 87.62 ± 0.12% inhibitory effect of edema after 21 days when linked with that of the standard drug. In the antidiabetic assay, ZnO-NPs sharply reduced glucose level in STZ-induced diabetic mice. In this study, the particle biocompatibility by human red blood cells was also determined. Keeping in view the biological importance of ZnO-NPs, we may readily get the conclusion that Paraclostridium benzoelyticum strain 5610-mediated ZnO-NPs will be a prospective antidiabetic, antibacterial, antiarthritic, and anti-inflammatory agent in vivo experimental models and can be used as a potent antidiabetic drug.

Antibacterial activities of zinc oxide nanoparticles: a mini review

Highly reactive oxygen species (ROS) are released from the surface of zinc oxide nanoparticles (ZnO NPs) which cause damage to the microorganisms. ROS may break down the cell wall and cell membrane of the bacteria leading to the leakage of cell contents causing their death. Antibacterial effect of ZnO NPs synthesized from plants’ extracts has been seen against several grampositive (Bacillus coagulans, Staphylococcus aureus, Bacillus subtilis) and gramnegative bacteria (Shigella dysenteriae, Sphingomonas paucimobilis, Salmonella typhimurium, Escherichia coli, Bacillus pumilus, Salmonella typhi). Zinc ions (Zn2+) freed from ZnO NPs may attack DNA and proteins of the cell, thus hindering the growth of the bacteria. The negative charge on the surface of some bacteria (E. coli, S. typhi) interacts with positively charged particles in ZnO NPs inhibiting the growth of these bacteria. The rate of antibiotic activity of ZnO NPs depends on size, the concentration of ZnO NPs, and the type of surfactant used in the synthesis of these ZnO NPs. Due to their antibiotic property, ZnO NPs can be used as antibacterial coating of inner surfaces of refrigerators and dishwashers, plastic food containers, in the lining of food cans used for packaging and preservation of food to prevent their spoilage.

Effect of garlic extract loaded on zinc oxide nanoparticles against Sarcocystis in vitro

The present study aimed to investigate the effect of garlic extract loaded on zinc oxide nanoparticles on the viability of Sarcocystis in vitro Samples of the parasite in the study was divided into three group inside to control group each one consists of 20 parasite in petri dish (5 petri dish) for each concentration contain the Phosphate Buffer Saline(PBS). The group treated with one concentration of the hybrid nanoparticles (Garlic extract loaded on zinc oxide nanoparticles) (0.1, 0.3, 0.5) mg/ml in 4 ᵒC and noticed the viability for five days. The nanoparticle measuring by SEM (Scaning Electronic Microscop) in Karbala University, College of Veterinary Medicine, the results showed that process of loading garlic Extract on the surface of zinc oxide nanoparticles was succeed and the hybrid nanoparticles had great effect (100%) in mortality of the parasite in high concentration 0.5 mg/ml followed by 0.3 mg/ml (8.98%) and (17.66%) in 0.1mg/ml. The statistical analytic results showed that there was significant increasing in mortality in all concentrations.

Effect of Polyethylene Film Thickness on the Antimicrobial Activity of Embedded Zinc Oxide Nanoparticles.

Microbial contamination of most foods occurs primarily at the surface during postprocessing and handling; therefore, preventing cross-contamination by incorporation of antimicrobial substances in contact with the surface of the product is an efficient strategy in reducing food contamination risks. Zinc oxide nanoparticles (ZnONPs) have been used widely to achieve antimicrobial films in various applications including the food industry. This work describes the fabrication of antimicrobial polymeric films containing ZnONPs produced by the coextrusion and dip-coating techniques. Effects of skin layer thicknesses containing ZnONPs on the antimicrobial effectiveness of the film by their capability to inactivate Gram-positive and Gram-negative bacteria were studied for both methods. The antimicrobial properties of the coextruded multilayer LLDPE/ZnONP nanocomposite films evidenced antimicrobial activity in the range 0.5–1.5 log reductions, while in the case of a sandblasted multilayer film, it showed high antimicrobial properties as around 99.99%. The optical properties of coextruded multilayer films were measured and discussed. Furthermore, to achieve a thinner LLDPE thickness, ZnONPs were coated with different concentrations of LLDPE solution by the dip-coating method. TEM confirmed that a homogeneous layer is formed on the surface of ZnONPs. The thickness of the LLDPE layer estimated by TEM was about 2 nm and film produced 3 log and 4 log reductions for E. coli and S. aureus, respectively. The results show that developed films have the potential to be used as food packaging films and can extend shelf life, maintain quality, and assure the safety of food. The antimicrobial mechanisms of ZnONPs were also investigated. It was found that direct contact of particles with products is necessary to assure high antibacterial activity of the films.

Biofilm-Resistant Nanocoatings Based on ZnO Nanoparticles and Linalool.

Biofilms represent an increasing challenge in the medical practice worldwide, imposing a serious threat to public health. As bacterial strains have developed antibiotic resistance, researcher’s attention has been extensively focused on developing more efficient antimicrobial strategies. In this context, the present study reports the synthesis, physicochemical characterization, ex vivo biodistribution, and in vitro evaluation of the capacity of nanostructured surfaces based on zinc oxide (ZnO) and biologically active molecules to modulate clinically relevant microbial biofilms. ZnO nanoparticles (NPs) were synthesized through a co-precipitation method without thermal treatment. The matrix-assisted pulsed laser evaporation (MAPLE) was applied for preparing nanostructured coatings based on ZnO NPs surface modified with linalool that were further characterized by X-ray diffraction (XRD), thermogravimetric analysis with differential scanning calorimetry (TGA-DSC), scanning electron microscopy (SEM), transmission electron microscopy with selected area electron diffraction (TEM-SAED), Fourier-transform infrared spectroscopy (FT-IR), and infrared microscopy (IRM). Histological analyses carried out at 7 days and 14 days after the intraperitoneal administration of linalool modified ZnO NPs revealed the absence of the latter from the brain, kidney, liver, lung, myocardium, and pancreas. Through in vitro assays on prokaryotic cells, it was proven that ZnO coatings hinder microbial biofilm formation of both Gram-positive and Gram-negative bacteria strains.

Effect of organic capping on defect induced ferromagnetism in ZnO nanoparticles

We report the possibility of room temperature d0Dilute Magnetic Semiconductor (d0DMS) behavior in organic capped Zinc Oxide (ZnO) nanoparticles. The uncapped and organic capped ZnO nanoparticles were prepared through a simple chemical synthesis technique. Tri-n-Octyl Phosphine Oxide (TOPO) and Dodecyle amine (DDA) were used as the capping agents. X-ray diffraction studies reveal that the organically capped nanoparticles were compressively strained. X-ray Photoelectron spectroscopy demonstrated that strain in the nanoparticles arise as the capping promotes vacancy sites for oxygen in ZnO nanocrystals. The magnetic measurements showed a room temperature ferromagnetic ordering in the as prepared ZnO nanoparticles samples. The observed ferromagnetism can be mainly attributed to positional defects in ZnO nanocrystals. In addition, the surface electronic configuration, which is modified by the capping molecules wrapped on the surface of ZnO nanoparticles, also has a key role in the origin of ferromagnetism.

Wound Healing Composite Materials of Bacterial Cellulose and Zinc Oxide Nanoparticles with Immobilized Betulin Diphosphate.

A design of new nanocomposites of bacterial cellulose (BC) and betulin diphosphate (BDP) pre-impregnated into the surface of zinc oxide nanoparticles (ZnO NPs) for the production of wound dressings is proposed. The sizes of crystalline BC and ZnO NPs (5–25%) corresponded to 5–6 nm and 10–18 nm, respectively (powder X-ray diffractometry (PXRD), Fourier-infrared (FTIR), ultraviolet (UV), atomic absorption (AAS) and photoluminescence (PL) spectroscopies). The biological activity of the wound dressings “BC-ZnO NPs-BDP” was investigated in rats using a burn wound model. Morpho-histological studies have shown that more intensive healing was observed during treatment with hydrophilic nanocomposites than the oleophilic standard (ZnO NPs-BDP oleogel; p < 0.001). Treatment by both hydrophilic and lipophilic agents led to increases in antioxidant enzyme activity (superoxide dismutase (SOD), catalase) in erythrocytes and decreases in the malondialdehyde (MDA) concentration by 7, 10 and 21 days (p < 0.001). The microcirculation index was restored on the 3rd day after burn under treatment with BC-ZnO NPs-BDP wound dressings. The results of effective wound healing with BC-ZnO NPs-BDP nanocomposites can be explained by the synergistic effect of all nanocomposite components, which regulate oxygenation and microcirculation, reducing hypoxia and oxidative stress in a burn wound.

Properties of Langmuir and immobilized layers of betulin diphosphate on aqueous solutions of zinc sulfate and on the surface of zinc oxide nanoparticles

This work examines the specific features of interaction of betulin diphosphate (BDP), exhibiting antitumor and wound-healing properties, with zinc cations during its immobilization on ZnO nanoparticles. The properties of Langmuir and transferred BDP monolayers from an aqueous subphase of zinc sulfate onto the surface of a solid substrate (CaF2, quartz) by the Langmuir—Schaefer method are investigated using IR and UV spectroscopy. It is shown that there is a twofold increase of the molecular area in the immobilized layers, while the compressibility modulus decreases by a factor of 1.5. Zinc oxide nanoparticles with immobilized BDP 10–20 nm in size (surface concentration of BDP is 100 mg g−1) retain the original hexagonal wurtzite structure. The efficiency of betulin diphosphate immobilized on the surface of zinc oxide nanoparticles is demonstrated in in vivo experiments for burn wounds in rats.

Enhanced antimicrobial and full-thickness wound healing efficiency of hydrogels loaded with heparinized ZnO nanoparticles: In vitro and in vivo evaluation

Nanotechnology-based fabricated wound dressings are known as appropriate substrates to enhance healing in both acute and chronic wounds. These types of materials have the ability to deliver therapeutic agents. In this study, a wound dressing including heparinized zinc oxide nanoparticles in combination with chitosan and poly(vinyl alcohol) was developed to investigate its antibacterial and regenerative properties in a rat model of full thickness skin wounds. By adding nanoparticles, the mechanical strength increased up to twice as compared to the sample without nanoparticles. In addition, heparin release profile follows the Hixson-Crowell release kinetic. Protein adsorption enhanced by adding nanoparticles in hydrogels and the prepared wound dressings were completely biocompatible. In terms of antibacterial activity, the minimum inhibitory concentration decreased by conjugation of heparin on the surface of zinc oxide nanoparticles compared to the non-functionalized nanoparticles, and, this shows the increased antibacterial synergistic effect by adding heparin to nanoparticles. Furthermore, it was found that the heparinized zinc oxide nanoparticles effectively accelerate wound closure, re-epithelialization and decrease collagen deposition compared to other groups after implantation. Hence, the prepared wound dressings have the capacity to significantly enhance healing of acute wounds.

Biosynthesis of Zinc oxide nanoparticles and their application for antimicrobial treatment of burn wound infections

The current study demonstrated the green fabrication of Zinc oxide nanoparticles (ZnO NPs) using the leaf extract of Coleus amboinicus (C. amboinicus) by an environment-friendly method. The leaf extract of C. amboinicus acts as capping and reducing agent during the fabrication of ZnO NPs. The prepared ZnO NPs were characterized by utilizing analytical techniques such as photoluminescence spectroscopy (PL), Transmission Electron microscopy (TEM), Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–vis) and x-ray diffraction spectroscopy (XRD). The XRD pattern confirmed the formation of polydisperse ZnO NPs having crystalline nature. The FTIR spectrum demonstrated the biomolecular capping on the surface of zinc oxide nanoparticles. The prepared ZnO NPs displayed excellent antimicrobial activities over several gram positive and gram-negative microbial pathogens. Further, wound healing studies in rats revealed that wound closure rate was greater in the ZnO NPs treated rats at all doses when related with the untreated group (negative control group), therefore, this indicates the effective wound healing ability of prepared ZnO NPs.

Adsorption of Albumin and Creatinine on ZnO Nanoparticles

This study focused on the adsorption of albumin and creatinine on the surface of zinc oxide nanoparticles. Factors affecting adsorption, like contact time, adsorbent dose, concentration, temperature, PH, and shaking rate, were studied. The best conditions for adsorption were found at 298k, pH = (7), the concentration of (2.25, 0.5x10-3)g/dL, (30, 2.5)min, and weight of zinc oxide NPs (30, 10)mg for both albumin and creatinine respectively. We found that adsorption corresponds to Langmuir adsorption isotherms for albumin and Temkin adsorption isotherms for creatinin. Thermodynamic parameters were determined (average of ΔG = -12563.57(J/mol.K), ΔH = 25.740(kJ/mol), average of ΔS = 126.37(J/mol)) for albumin and (average of ΔG = -3348.45(J/mol.K), ΔH = 36.731(kJ/mol), average of ΔS = 132.22(J/mol)) for creatinine, Through the results of )ΔG(, the system is spontaneous because of the negative values. Positive ) ΔH( value clarify that process is endothermic. While ΔS value refers to the system is more random, the results also show that the adsorption type was physical, which means that it is multilayered. The type of bonding force between the molecules is Vander Waals force.

Significant Reduction of Defect States and Surface Tailoring in ZnO Nanoparticles via Nano-Bio Interaction With Glucose for Bio-Applications.

In this study, we have investigated the structural and optical properties of nanoconjugates (NJs) consisting of phase pure zinc oxide (ZnO) nanoparticles (NPs) with glucose biomolecules. All NJs were fabricated using a standard biochemical synthesis process. Structural, optical, vibrational, and biochemical interface properties of nano-bio composites are probed by different complementary characterization techniques. The XRD patterns of the NPs and NJs illustrate a highly phase pure ZnO structure. A visible green emission in the photoluminescence spectrum, mainly associated with the oxygen vacancies on the surface of ZnO nanostructure, is significantly reduced by the incorporation of glucose biomolecules. The strong binding interaction of glucose biomolecule on the surface of ZnO NPs results in the reduction in green-yellow-orange emission intensities. The interaction of glucose molecules modifies oxygen vacancies by capturing free electrons from the ZnO surface region. Significant changes in the peak intensity and relative peak position of some of the glucose and ZnO NPs in Raman spectra refer to the direct binding between these two nano- and bio-components. In the X-ray photoelectron spectroscopy, the binding energy of O 1s core level in NJs increases from 531 eV (O 1s core level position for ZnO) and the increment is more with higher initial glucose concentration in the solution during synthesis. This study serves as a promising platform for the development of new kinds of NJs and investigation of their interfacial properties which can take the frontier forward for integration and multifunctionality.

Response Surface Modeling of Electrochemical Data for Sensitive Determination of Sudan III in Food Products at the Surface of a Nanocomposite Modified Electrode

In this work, application of a sensitive electrochemical technique assisted with multivariate optimization methods is presented for detection of Sudan III in food samples. At first, the synthesis and characterization of zinc oxide nanoparticles (ZnONPs) are described. The precipitation method is used for synthesis of ZnONPs with average particle sizes ranging from 20 to 30 nm. The structural analysis of the samples is performed using XRD. Also, the morphology and particle sizes of the ZnONPs are confirmed by SEM. Next, the nanoparticles are used for modification of a carbon paste electrode (CPE) surface. The modified electrode is used for investigation of electrochemical behavior of Sudan III. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) techniques are applied for characterization of the nanostructure modified electrode. For achieving the best response for Sudan III, effective experimental factors on the voltammetric determination of the analyte are optimized by rotatable central composite design (RCCD) and response surface methodology (RSM). The nanostructured modified electrode shows an excellent electrocatalytic property on the oxidation peak current of Sudan III. The electrochemical behavior of Sudan III at the surface of zinc oxide nanoparticles modified carbon paste electrode (ZnONPs/CPE) are investigated by differential pulse voltammetry (DPV), cyclic voltammetry (CV), and chronocoulometry. Analytical parameters such as linearity, selectivity, repeatability, and stability are also investigated. At the optimized conditions, the linear dynamic ranges for Sudan III are obtained 0.05–1.0 and 1.0–15.0 μM and the detection limit is achieved 2.56 nM. Also, the proposed sensor is successfully applied for detection of Sudan III in real complicated samples.

Chemometrics-assisted determination of Sudan dyes using zinc oxide nanoparticle-based electrochemical sensor

Multivariate curve resolution-alternating least squares (MCR-ALS) assisted with electrochemical techniques was applied for simultaneous determination of Sudan II and III at a surface of zinc oxide nanoparticles (ZnONPs) modified carbon paste electrode. Characterization of the ZnONPs and the nanostructured modified electrode was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Response surface methodology using central composite rotatable design was employed to design of experiments and achieving to optimum values of variables. For simultaneous determination of Sudan II and III, electrochemical second order data were obtained by changing of pulse height in differential pulse voltammetry technique. MCR-ALS was performed on the data to obtain the decomposition peaks of analytes. Then, the detection limits were obtained 1.87 and 2.62 nM for Sudan II and III, respectively. Finally, this method used for the analysis of the two analytes in real samples.

Charge transfer-induced photoluminescence in ZnO nanoparticles.

The quality of solution-processed zinc oxide (ZnO) nanoparticles (NPs) is often correlated with their photoluminescence (PL) spectral characteristics. However, the reported PL spectral characteristics lack consistency and remain controversial. Here we report that "defect-emission free" PL spectra can even be obtained in thin films composed of as-synthesized ZnO NPs. It is found that both the PL spectral line-shape and intensity are extremely sensitive to nitrogen and oxygen. By conducting time-dependent PL (t-PL) and photothermal deflection spectroscopy (PDS) measurements under vacuum and different gases, it is proposed that both inert (N2) and reactive (O2) molecules can be absorbed on the ZnO NP surface and induce charge transfer (CT). The CT states induced by N2 are non-radiative which significantly reduces the band emission. Whereas the CT states induced by O2 are radiative at the visible region, and the exciton transfer is efficient which increases the overall PL quantum yield. Owing to such effects, the previously reported correlation between defects and PL emission becomes questionable and needs to be revisited. Particularly, the visible emission from the ZnO NPs is proved to be facilitated by external effects, instead of direct recombination from defect states.