Spherical ZnO Research Articles

Effect of Fe Substitution on Dielectric, Electrical and Photocatalytic Behavior of ZnO Nanoparticles

Aims: To develop a simple and cost effective synthetic strategy for the preparation of Fe substituted ZnO nanoparticles. Background: The optoelectronic, electrical, dielectric, optical and magnetic properties of nanocrystalline transition metal substituted ZnO are being explored worldwide for a variety of applications in optoelectronic devices, solar cells, transparent thin film transistors, ultraviolet photodetector, piezoelectric devices, light emitting diodes as well as in the biomedical field. Fe substituted ZnO nanoparticles are being looked upon as promising material in dilute magnetic semiconductor system. Objective: To establish chemical identity and purity in order to ensure the complete substitution of Fe3+ in ZnO lattice and study the effect of Fe substitution on dielectric, electrical and photocatalytic behavior of ZnO nanoparticles. Methods: The nearly spherical ZnO and Fe substituted ZnO nanoparticles were synthesized at a low temperature via solution combustion synthesis employing metal nitrate and sucrose. Results: The powder X-ray diffraction measurement has revealed the monophasic character and complete substitution of Fe in the wurtzitic ZnO lattice. The lattice constants and aspect ratio of Fe substituted ZnO were nearly constant and comparable to that of pristine ZnO. The average crystallite size was found to decrease with increasing Fe substitution. SEM images revealed porous spongy network like morphology. TEM measurements revealed a nearly spherical particle with narrow size distribution between 10 nm - 25 nm. Conclusion: The dielectric constant and dielectric loss decrease upto x = 0.04 and increases with further increase in Fe concentration. The lower value of dielectric loss in the higher frequency region indicates the less lossy nature of Fe substituted samples. AC conductivity behaviour suggests small polaron hopping type of conduction mechanism. The RT DC resistivity was found to decrease with increasing Fe substitution. Pristine ZnO displayed very high degradation efficiency for photodegradation of MB dye. The photodegradation efficiency was found to decrease considerably with increasing Fe substitution.

Synthesis and growth of spherical ZnO nanoparticles using different amount of plant extract

The use of plant extracts has become an interesting ecofriendly method to synthesize and stabilize the different structures nanoparticles (NPs). This work investigated the effect of plant extract as a reducing and stabilizing agent on the growth and morphology of ZnO nanoparticles (ZnO-NPs). Green synthesis and growth of spherical ZnONPs was carried out by co-precipitation method using a Zinc acetate salt and various amounts of Azadirachta indica seed husk extract (20 ml and 40 ml). The synthesized ZnO-NPs were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM-EDX), and transmission electron microscopy (TEM). The FTIR analyses revealed the presence of Phenolic alcohol, amines and carboxylic acid groups and ZnO in synthesized NPs with more intense peaks at higher amount (40 ml) of A. indica extract. Also, structural morphology analyses using SEM revealed uniform spherical shaped particles with diameter from 25 to 60 nm (20 ml of extract) and 19 to 35 nm (40 ml of extract) for ZnO-NPs. The EDX spectral revealed that the required phase of Zn and O was present 69.54% (Zn) and 30.46% (O) at 20 ml of extract, also 73.71% (Zn), 26.26% (O) at 40 ml of extract respectively and confirmed high purity for the synthesized ZnO NPs. TEM revealed spherical shaped NPs with diameter ranging from 28 to 52 nm (20 ml of extract) and 8.2 to 11.9 nm (40 ml of extract) respectively, with a trend reduction in particle size of NPs at higher amount of A. indica seed extract (40 ml) and growth of more uniform particles with no agglomeration. The study showed successful growth of spherical ZnO-NPs with required properties at a higher amount of extract.

Comparative structural and electrochemical study of spherical ZnO with different tap density and morphology as anode materials for Ni/Zn secondary batteries

In this work, we compare the behavior of five kinds of high-density spherical ZnO with different surface morphology as anode materials for nickel/zinc rechargeable batteries to investigate the effects of microstructure and surface properties of ZnO on the electrochemical performance of zinc anodes. For the first time, five spherical ZnO samples with tap densities of 1.62, 2.00, 2.38, 2.83, and 3.12 g cm−3 have been successfully developed via a complexing co-precipitation method by adjusting the composition of alkaline solution and pH value. It is discovered that an enhanced volume specific capacity and more stable cycling performance can be achieved for the anode with spherical ZnO (3.12 g cm−3). Nevertheless, the as-obtained ZnO sample with higher tap density shows slightly worse high-rate performance and lower discharge capacity. Interestingly, as confirmed by the CV and Tafel polarization test, with the increase of ZnO’s tap density, the zinc anodes exhibit better reversibility and higher corrosion resistance. Consequently, the denser solid spherical structure of spherical ZnO is beneficial to effectively adjust its “dissolution-deposition” process, significantly suppressing the outward growth of zinc dendrites and enhancing the batteries’ cycling stability.

Silicon dots films deposited by spin-coating as a generated carrier addition layer of third generation photovoltaics

In this work, silicon ink composing of silicon powder and zinc oxide solution was formulated and spin-coated on quartz and n/p-Si substrates followed by drying the films under atmosphere at the temperature of 550 ​°C. The results showed that this top-addition layer could be the highly promising layer for photo-generating carriers in third-generation photovoltaics to enhance blue-light absorption. X-ray diffraction and scanning electron microscopy techniques were used to study the presence of silicon and zinc oxide nano-crystallites. The thin films consisting of different energy bandgap of Si nanocrystals (~100 ​nm) with narrow bandgap and spherical ZnO:Bi nanocrystal (~20 ​nm) with wider bandgap could be obtained from the evidence of bandgap enlargement. The band gaps of the thin films were tunable by adjusting silicon dots density in ZnO:Bi film. Energy upshift of light absorption edge depended on the silicon dots density was observed in the range 1.6–3.3 ​eV related band gap enlargement by Tauc plot. Under illumination, a high photocurrent gain of the thin film comprised of low Si dots density coated on a quartz substrate was about 103 times higher compared with its dark current. This result is agreeably explained in terms of its lower superficial trap states at the interface between silicon and zinc oxide matrix. The composite layer can be applied to a third-generation solar cell with the efficiency 1.50% higher than that with a typical crystalline-Si solar cell.

Microwave-assisted synthesis of La/ZnO hollow spheres for trace-level H2S detection

Abstract Hollow spherical ZnO architectures and La-decorated ZnO materials with different amounts (0.2, 0.5, 0.8, and 1 at% La) were successfully synthesized by a simple one-step microwave-assisted synthesis method. The porous surface of the hollow sphere provided favorable conditions for gas adsorption and diffusion. The sensing performance of these gas sensing materials were systematically evaluated. The enhancement effect of La decoration on the gas sensing properties of the ZnO-based sensor to H2S was investigated. The 0.5 at% La/ZnO exhibited a high response to H2S at the operating temperature of 150 °C, and the response value was approximately 176.3 to 5 ppm H2S. The sensor based on 0.5 at% La/ZnO also has excellent selectivity to H2S at 150 °C, and the detection limit of is as low as 50 ppb, which is important for trace-level H2S detection.

Antibacterial and anticancer activity of ZnO with different morphologies: a comparative study.

ZnO nanoparticles (NPS) with different morphologies were synthesized, and the antibacterial and anticancer activity was studied, herein. The physicochemical characterization was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and UV-visible. To study the antibacterial and anticancer capability of ZnO NPS, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria and HeLa cancer cells were exposed at different doses of ZnO NPS (7-250µg/mL). TEM analysis confirmed the obtention of spherical, hexagonal and rod ZnO NPS with an average diameter of 20 ± 4nm, 1.17 ± 0.3µm and 1.11 ± 1.2µm, respectively. XRD diffractograms showed the characteristic pattern of crystalline ZnO in wurtzite phase. FTIR and UV-vis spectra showed slight differences of the main absorption peaks, revealing that different ZnO NPS morphologies may cause shifts in spectra. Biological essays showed that the number of E. coli and S. aureus bacteria as well as HeLa cells decreases linearly by increasing the nanoparticle concentration. However, the best anticancer and antibacterial activity was shown by spherical ZnO NPS at 100µg/mL. The better capability of spherical ZnO NPS than hexagonal and rod ZnO NPS is related with its small particle size. The present results suggest that the spherical ZnO NPS has a great potential as an antibacterial and anticancer agent.

Mosaic structure ZnO formed by secondary crystallization with enhanced photocatalytic performance

Zinc acetate is used as a raw material to synthesize the desired ZnO in hot solvent by controlling the amount of citric acid (CA) added. Notably, the amount of CA added has a significant relationship with the control of the morphology of ZnO. Spherical ZnO wrapped in nanosheets is synthesized through the secondary crystallization of Zn2+. The optical properties of the ZnO sample are tested through the degradation of organic pollutants. Notably, the photocatalytic properties of ZnO vary with the different amounts of CA added. Exposure of the active crystal face increases the photocatalytic activity of ZnO. In addition, the number of defects on the surface of the ZnO sample increases because of its large specific surface area, thus changing the bandgap of ZnO. Therefore, the resulting sample can respond under visible light.

Process Study on Surface Modification of Coral Hydroxyapatite

Objective: To explore process of modifying coral hydroxyapatite by nmZnO under different conditions, the final plan is to develop a porous artificial bone composite that combines the antibacterial properties of nano zinc oxide with the porous biodegradability of coral hydroxyapatite. Methods: Coral hydroxyapatite was modified by zinc nitrate sol-gel method at 70°C in weak acid environment. White granular porous composite materials were obtained by ultrasonic, rotary stirring, drying and calcination. The composition of the composite material is analyzed using X-ray diffractomer (XRD), using scanning electron microscopy (SEM) to observe and analyze changes in the surface appearance of composite materials, using energy dispersive X-ray spectroscopy (EDX) to observe and analyze the composition of the composite surface, the results of thermogravimetric analysis were used to study the decomposition temperature and other characteristics of the composite. Results: The sol-gel method can be used for antibacterial modification on CHA surface. When the mass ratio of coral hydroxyapatite, zinc nitrate and PEG-6000 is 48:4:5, the particle size and distribution of nano-zinc oxide particles are ideal, and uniformly distributed spherical ZnO nanoparticles can be observed under scanning electron microscopy. Conclusion: Coral hydroxyapatite surface could be modified by zinc nitrate sol-gel method. The particle size of nano zinc oxide is less than 100 nanometers. The agglomeration problem of nano-particles is solved; the porous structure of CHA are not destroyed.

N-/S- dual doped C@ZnO: An excellent material for highly selective and responsive NO2 sensing at ambient temperatures

• The sensing properties of N/S dual doped C@ZnO is investigated for the first time. • Noble metal free sensing material with high sensitivity towards NO 2 at 25 °C. • The N/S dual doped C@ZnO composite exhibits excellent NO 2 selectivity. • N/S dual doped C significantly enhanced the sensing performance of ZnO. • Plausible gas sensing mechanism has been proposed. Nitrogen dioxide (NO 2 ) is an extremely toxic gas and harmful to human health and the environment. Inhalation of NO 2 reduces immunity to lung infections and causes respiratory problems such as wheezing, coughing, colds, flu, and bronchitis. To date, several sensors have been developed for the detection of NO 2 . Indeed, the development of highly sensitive and selective room temperature sensor with rapid response and recovery time could be called an “innovation” for metal oxide-based gas sensors for environmental remedy applications. Herein, we prepared ZnO nanospheres (ZNS), nitrogen-doped carbon-coated ZnO spheres (NC@ZNS), sulfur-doped carbon-coated ZnO spheres (SC@ZNS), and nitrogen-sulfur dual doped carbon-coated ZnO spheres (NSC@ZNS) for NO 2 sensing. Among them, the NSC@ZNS exhibits excellent NO 2 sensing characteristics with the sensor response (S R = R g /R a ) of 730.4 and 31.2 at 100 and 25 °C, respectively. The limit of detection (LOD) of the NSC@ZNS sensor is ~21 ppb at ambient temperature. The NSC@ZNS hybrid nanocomposite sensor exhibits ultrafast response and recovery times of ~88 s and 305 s to 500 ppb of NO 2 at 25 °C. Besides, the NSC@ZNS sensor shows excellent selectivity to NO 2 , which is ~31 times higher than other interfering gases. The enhanced sensing characteristics of the NSC@ZNS sensor is attributed to the synergy between the nitrogen-sulfur dual doped carbon and hierarchical mesoporous ZnO. The selective detection of NO 2 with significantly rapid response and recovery time at 25 °C makes for intriguing the promising practical applications of our proposed NSC@ZNS sensor.

ZnO Quantum Dots: Broad Spectrum Microbicidal Agent Against Multidrug Resistant Pathogens E. coli and C. albicans

Infectious microbial diseases are leading causes of morbidity and mortality worldwide. Further, emergence of Multidrug resistance (MDR) in microbes has posed a critical concern for public healthcare and microbial therapeutics. Nano-based drug compositions might be ideal candidates to address the challenges of microbial drug resistance. Herein, we synthesized monodispersed, spherical ZnO quantum dots (QDs) of average diameter 5-6 nm as biosafe, nanomicrobicidal agent against MDR pathogens. The broad spectrum microbicidal potential of ZnO QDs was evaluated against Extended Spectrum Beta Lactamase (ESBL) producing MDR isolates of E. coli (with resistance to antibiotics of different classes viz. third & fourth generation of cephalosporin, penicillin, monobactams and quinolones) and MDR isolates of C. albicans (MDR strains had evolved from sensitive strains acquiring resistance). ZnO QDs exhibited dose dependent, broad spectrum microbicidal activity against all MDR isolates of E. coli and C. albicans. Highly reduced growth was observed in all MDR isolates of E. coli and C. albicans at minimum inhibitory concentration (MIC) of 200 µg/ ml ZnO QDs and the growth was further reduced in presence of 250 and 400 μg/ ml of ZnO QDs for E. coli and C. albicans, respectively. To the best of our knowledge, microbicidal potential of ZnO QDs against microbial strains exhibiting MDR for currently used drugs has not been studied. Results of present study indicate that ZnO QDs might be promising as next generation broad spectrum alternative for combating MDR in microbial pathogens.

A facile construction of heterostructured ZnO/Co3O4 mesoporous spheres and superior acetone sensing performance

The rapid development of internet and internet of things brings new opportunities for the expansion of intelligent sensors, and acetone as a major disease detection indicator (i.e., diabetes) making it become extremely important clinical indicator. Herein, uniform mesoporous ZnO spheres were successfully synthesized via novel formaldehyde-assisted metal-ligand crosslinking strategy. In order to adjust the pore structure of mesoporous ZnO, various mesoporous ZnO spheres were synthesized by changing weight percentage of Zn(NO3)2·6H2O to tannic acid (TA). Moreover, highly active heterojunction mesoporous ZnO/Co3O4 has been fabricated based on as-prepared ultra-small Co3O4 nanocrystals (ca. 3 nm) and mesoporous ZnO spheres by flexible impregnation technique. Profit from nano-size effect and synergistic effect of p-n heterojunction, mesoporous ZnO/Co3O4 exhibited excellent acetone sensing performance with high selectivity, superior sensitivity and responsiveness. Typically, 5 wt% Co3O4 embedded mesoporous ZnO sphere showed prominent acetone response (ca. 46 for 50 ppm), which was about 11.5 times higher than that in pure ZnO sensing device, and it was also endowed high cyclic stability. The nanocrystals embedded hybrid material is expected to be used as promising efficient material in the field of catalysis and gas sensing.

Polariton condensation and surface enhanced Raman in spherical ZnO microcrystals

Preparation and characterization of polariton Bose–Einstein condensates in micro-cavities of high quality are at the frontier of contemporary solid state physics. Here, we report on three-dimensional polariton condensation and confinement in pseudo-spherical ZnO microcrystals. The boundary of micro-spherical ZnO resembles a stable cavity that enables sufficient coupling of radiation with material response. Exciting under tight focusing at the low frequency side of the bandgap, we detect efficiency and spectral nonlinear dependencies, as well as signatures of spatial delocalization of the excited states which are characteristics of dynamics in polariton droplets. Expansion of the photon component of the condensate boosts the leaky field beyond the boundary of the ZnO microcrystals. Using this, we observe surface polariton field enhanced Raman responses at the interface of ZnO microspheres. The results demonstrate how readily available spherical semiconductor microstructures facilitate engineering of polariton based electronic states and sensing elements for diagnostics at interfaces.

Photocatalytic degradation of Rhodamine-B under visible light region by ZnO nanoparticles loaded on activated carbon made from longan seed biomass

In the present study, the synthesis of ZnO/LSAC through pyrolysis of the carbonized material prepared from longan seed, zinc acetate in alkaline medium. The obtained materials was characterized by means of XRD, SEM, TEM, BET and UV-Vis-DRS. The XRD patterns of ZnO/LSAC nanocomposites were assigned to wurtzite structure of ZnO with crystallite size about 15 to 30 nm. SEM and TEM observations showed the spherical ZnO particles formed on the activated carbon. The band gap energy and specific surface area of ZnO/LSAC were found to be 2.79 eV and 294.4 m2/g, respectively. The photocatalytic activities of the prepared materials were evaluated for the degradation of Rhodamine B (RhB) dye. The removal of RhB was found to be pH dependent, and the optimized removal efficiency reached to 93.75% and the mineralization level was over 84,09% at initial RhB concentration of 40 mg.L-1 and pH 7 following 120 min under visible-light illumination. The kinetic studies showed the decolorization of RhB followed pseudo first-order kinetics with the rate constant were determined kapp = 1.67x10-2 min−1.

Effects of Inorganic ZnO Particle Doping on Crystalline Polymer Morphology and Space Charge Behavior

This study further investigated the synergistic effect of micro- and nanofiller doping on matrix material space charges and breakdown characteristics. Accordingly, low-density polyethylene (LDPE) was used as the matrix material, and spherical ZnO particles with sizes of 30 nm and 1 µm were used as additives. Micro-ZnO/LDPE, nano-ZnO/LDPE, and micro-nano-ZnO/LDPE composites were prepared through melt blending. The crystalline morphologies of the composites were observed via polarized light microscopy. The composite crystallinity and melting peak temperature were measured via differential scanning calorimetry, and the micro- and nanoparticle dispersions in the matrix were observed via scanning electron microscopy. The test results showed that the particles were uniformly dispersed in the polyethylene matrix. The filler acted as a heterogeneous nucleation agent in the matrix. The crystal size decreased, thereby increasing the crystal quantity. The doping of inorganic ZnO particles improved the composite crystallinity. The ZnO/LDPE composites were subjected to DC breakdown, space charge, and dielectric spectrum tests. When the crystal arrangement of the sample was loose and its size was large, the breakdown process developed along a shorter path, and the field strength of the composite breakdown decreased. The order of AC and DC breakdown field strengths of the samples was as follows: micro-ZnO/LDPE < pure LDPE < micro-nano-ZnO/LDPE < nano-ZnO/LDPE. The DC and AC breakdown field strengths of the micro- and nano-ZnO/LDPE were 4.7% and 3.2% higher than those of the pure LDPE, respectively. Moreover, the DC and AC breakdown field strengths of the nano-ZnO/LDPE were 11.02% and 15.8% higher than those of the pure LDPE, respectively. The doping of inorganic ZnO particles restrained the space charge accumulation, and the residual charges decreased after short-circuit treatment. The dielectric constant of all nanocomposites was lower than that of LDPE, and the dielectric loss of all composites was higher than that of LDPE.

Antibacterial activity of Metal nanoparticles produced by Streptomyces spp. Isolated from soil samples

Twenty-five soil samples were collected from Hilla city. (10) Actinomyctes isolates were isolated. Five Streptomyces spp. Late was diagnosed. Isolates positive for a gram and having grey Aerial Mycelium and yellow-green Substrate mycelium on yeast-malt extract medium. All Streptomyces spp. olates d for nanoparticles production. Streptomyces spp.2 was able for producing of omyces spp.2 was, grey aerial, yellow-green substrate mycelium, unable for in producing, having the ability for using glucose, sucrose, mannitol, negative for fructose and mannose, negative for indole, and vogas Proskauer, positive for methyl red test and citrate utilization, negative for catalase and urea test. UV spectrum for ZnO particles showed maximum absorption at 418 nm. FT-IR spectrum for ZnO nanoparticles represented absorption peak at 3425.58 cm-1 is O-H group, 2360.87 cm-1 is CΞC , 1678.07 cm-1 is C=O group, 1388.75 cm-1 is C-H group,1089,78 cm-1 is C-O bending, 1006.84 cm-1 is C-O stretching,615.36 cm-1 is C-H, and 545.86 cm-1 is C-cl stretching. SEM shows the ability of Streptomyces spp.2 for spherical ZnO nanoparticles synthesizing with size (78.96) nm. Streptomyces spp.2 ZnO nanoparticles were having a great effect on E.coli, with inhibition zone (20 mm) and (15,18) mm against S.aureus, Klebsiella pneumonia.

Plasmonic ZnO/Au/g-C3N4 nanocomposites as solar light active photocatalysts for degradation of organic contaminants in wastewater

In the present study, novel ZnO/Au/graphitic carbon nitride (g-C3N4) nanocomposites were fabricated via a facile and eco-friendly liquid phase pulsed laser process followed by calcination. Notably, the approach did not necessitate the use of any capping agents or surfactants. The as-prepared photocatalysts were evaluated by various electron microscopy and spectroscopy techniques. The obtained results confirmed good dispersion of the Au nanoparticles (NPs) on the surface of spherical ZnO particles deposited on the g-C3N4 nanosheets. The ZnO/Au/g-C3N4 nanocomposite exhibited substantially enhanced catalytic activity toward the degradation of methylene blue (MB) under simulated solar light irradiation. In particular, the ZnO/Au15/g-C3N4 composite containing 15 wt% Au displayed a rate constant, which was approximately 3 and 5 times greater than those of pristine g-C3N4 and ZnO, respectively. This improved photocatalytic activity of ZnO/Au15/g-C3N4 was attributed to the surface plasmon resonance of Au NPs and the synergistic effects between ZnO and g-C3N4. The boundary between ZnO/Au and g-C3N4 enabled direct migration of the photogenerated electrons from g-C3N4 to ZnO/Au, which hindered the recombination of electron–hole pairs and enhanced the carrier separation efficiency. Additionally, a plausible MB degradation mechanism over the ZnO/Au/g-C3N4 photocatalyst is proposed based on the results of the conducted scavenger study.

Carbon quantum dots supported ZnO sphere based photocatalyst for dye degradation application

A Carbon quantum dots supported ZnO hollow Sphere (ZnO/C-dots) were synthesized through a solvothermal method using polyethylene glycol 400 (PEG 400) as a solvent. The phase and crystal structure of as-prepared ZnO/C-dots photocatalyst were characterized by powder X-ray diffraction (XRD). The surface morphology and size of the composite were analyzed using field emission scanning microscopy (FE-SEM). The optical properties of the as-prepared nanocomposites were examined using UV–visible (UV–Vis) spectrometer. The photocatalytic activity of pure ZnO and ZnO/C-dots nanocomposites were evaluated by the degradation of methylene blue (MB) under UV–Visible light irradiation. The ZnO/C-dots nanocomposites exhibited maximum photocatalytic MB dye degradation efficiency of 96% which is much higher that the pure ZnO (63%). The enhanced photocatalytic activity of ZnO/C-dots is due to the extended light absorption in the visible region and suppressed photoexcited electron-hole pair recombination rate. Moreover, the activity of photocatalyst after five cycles exhibits high stability, which is vital for the sustainable photocatalytic procedures. It is concluded that the prepared ZnO/C-dots composite have low cost, good stability and has a great potential application for Photocatalytic dye degradation.

ZnO@graphene oxide core@shell nanoparticles prepared via one-pot approach based on laser ablation in water

Core-shell nanoparticles (NPs) have attracted tremendous attention due to their tunable properties and numerous potential applications. However, preparation of uniform and size-controlled core-shell nanomaterials of ZnO with graphene oxide (GO) is still considered as a challenging task even after years of research. In this work, we report on a facile one-pot organics-free method for preparation of GO-wrapped ZnO NPs. Laser ablation of zinc and carbon targets in water medium at ambient atmosphere resulted in formation of spherical ZnO core and GO shell, respectively. According to Raman active modes, the GO shell was layered and the ZnO core was polycrystalline. Both Raman spectra and X-ray diffraction patterns revealed that formation of layered GO increased stress inside the ZnO core. Surface layers reduced the density of defects and disorders in the ZnO crystal lattice and enhanced the phonon lifetime. Also, the minimal interfacial disorder between the layered GO and ZnO core resulted in continuous formation of a GO layer. Thus, laser ablation in liquid is demonstrated to provide stable and uniform core-shell GO@ZnO NPs with controlled GO layer that can find applications in biomedical and sensing fields.

Adsorption behavior of barium ions onto ZnO surfaces: Experiments associated with DFT calculations

This work aimed to evaluate and optimize parameters for the removal of barium (Ba2+) ions on ZnO spherical nanoparticles. Spherical ZnO nanoparticles was fabricated using over-simplistic applying arabinose sugar followed by evaporation methods. The physicochemical properties of the ZnO nanoparticles were studied using XRD, SEM, EDX, and FTIR. The maximum adsorption capacity of Ba2+ by ZnO nanoparticles was 64.6 mg/g. In isotherm studies, the Langmuir model is well-fitted to the sorption data. Kinetic pseudo-second-order models best illustrated the adsorption mechanism of barium (Ba2+) ions. Based on the density functional theory calculation, the barium (Ba2+) ion adsorption onto the ZnO surface is strong chemisorption with an exothermic adsorption energy of -291.3 kJ/mol.

Surface-state-mediated interfacial charge dynamics between carbon dots and ZnO toward highly promoting photocatalytic activity.

Design of hybrid systems for photocatalytic application tends to be restricted by lacking interfacial coupling and fast charge recombination in the body competing with interface dynamics. In this work, the reduced carbon dots (rCDs) with numerous surface hydroxyl groups were deliberately anchored onto flower-like ZnO spheres with a highly exposed surface area to form heterointerfaces with sufficient interfacial electronic coupling. The incorporated rCDs evidently promote the light harvesting and charge separation of the binary hybrid system, resulting in highly enhanced photocatalytic Cr(VI) degradation performance. Ultrafast time-resolved spectra reveal that the surface C-OH bonds of rCDs play a crucial role at the heterointerfaces to regulate the charge dynamics. The long-lived surface C-OH states not only act as electron donors but also become electron mediators to rapidly capture the photoelectrons from the intrinsic state in the time-domain of 1 ps and induce a much longer lifetime for achieving highly efficient photoelectron injection from rCDs to ZnO. These results manifest that rCDs can be a promising photosensitizer to apply in photocatalytic pollutant treatment and energy conversion fields.