ZnO NFs Research Articles

The Synthesis of MOFs of ZnImBImZnO through Hydrothermal and Solvothermal Methods

Metal-organic frameworks (MOFs) are a promising class of materials that have a wide range of applications, from gas storage to catalysis. The synthesis of MOFs from the ZnImBImZnO framework has been carried out using hydrothermal and solvothermal methods. By using different metal-ligand molar ratios and solvents, we have discovered that MOFs can be formed both in DMF and water solvents. The products obtained were studied using various techniques, including SEM, PSA, and FTIR, to confirm their formation Our research has shown that MOFs synthesized with different concentrations and solvents show different size distributions. This suggests that the choice of solvent and concentration can be used to control the size and morphology of the MOFs. Furthermore, we have found that the formation of the MOFs framework also directs the morphology of the Zn(II)-imidazole complex and ZnO NFs. Our results provide important insights into the synthesis and properties of MOFs. Moreover, the contact angle measurement data for the ZnImBImZnO framework indicates that it is unequivocally hydrophilic. By understanding the factors that influence the properties of MOFs, we can design new materials with specific properties tailored to different applications. This exciting research area has the potential to revolutionize many fields, from energy storage to drug delivery. Our results provide important insights into the properties of MOFs and pave the way for developing new materials with tailored properties.

Impact of reduced-graphene-oxide functionalization of flower-like zinc-oxide nanostructures on sensing performance of resistive ethanol gas sensor

This research presents a sensitive resistive ethanol gas sensor based on reduced graphene oxide (rGO)-functionalized Zinc oxide nanoflowers (ZnO NFs). Upon completion of synthesis, the resulting nanostructures were cast onto the photolithographed silver interdigitated electrodes positioned on an Al2O3 substrate. The graphene oxide (GO) with a low oxidation degree was synthesized using a Hummer's method. In the pursuit of optimizing sensing performance, rGO-functionalized ZnO NFs were synthesized through a one-pot hydrothermal process, utilizing different initial quantities of GO (0 mg, 2 mg, 8 mg, and 12 mg). According to the gas sensing measurements, the fabricated sensor with 8 mg initial GO showed the highest response to ethanol at 250 °C. The results show that the GO addition reduced the optimal working temperature of the pure ZnO NFs from 350 °C to 250 °C. The sensor exhibited a good selectivity, repeatability, and high long-term stability. Enhanced ethanol sensing response of the optimized gas sensor was related to the formation of p-n heterojunction between p-type rGO (formed during hydrothermal process at 200 °C) and n-type ZnO and the presence of the optimal amount of rGO on the surface of NFs. The results obtained in this investigation stress the significance of pinpointing the optimal quantity of GO for producing rGO-ZnO nanoflowers with the highest possible sensitivity to ethanol gas.

انماء تراكيب نانوية من أكسيد الزنك بطريقة التحلل المائي الحراري لقيم مختلفة من درجة الحامضية

تم تحضير تراكيب نانوية (زهرية وعصي) الشكل من اكسيد الزنك بالطريقة الحرارية المائية عند 90 درجة مئوية لمدة ثلاث ساعات. تم تحضير ثلاثة محاليل بقيم درجة الحامضية 9 و10 و11 وبمولارية 0.028 مولاري، على قواعد زجاجية / بذور ZnO. كان لجميع العينات المحضرة نمط حيود متعدد التبلور مع حيود سائد من المستوى (002). مع زيادة درجة الحامضية، زاد حجم البلوري إلى حد أقصى قدره 37.6 نانومتر. أظهرت صور الانبعاث الحقلي لمجهر الماسح الإلكتروني تكمن اهمية البحث في انماء تراكيب مختلفة من اكسيد الزنك من خلال التحكم بدرجة الحامضية حيث أظهرت النتائج ظهور تراكيب زهرية عند الحامضية 11 وبحجم جسيمي 100-800 نانومتر، وانماء تراكيب نانوية بشكل حزمة من العصي عند الحامضية 10 وبحجم جسيمي 500-800 نانومتر وانماء اكسيد الزنك بشكل عصي منفردة عمودية على السطح عند الدرجة الحامضية 9 وبحجم حبيبي 70-80 نانومتر. أظهرت الخصائص البصرية انخفاضًا في النفاذية من 78.75 الى 79.32 وزيادة في قيم فجوة الطاقة من 3.18 الكترون فولط الى 3.31 الكترون فولط مع زيادة درجة الحامضية.

Shelf-life enhancement of Gerbera jamesonii flowers by the green synthesised ZnO nanoflowers

ABSTRACT This study has been aimed to synthesise the self-assembled, flower-shaped zinc oxide nanoparticles (ZnO NFs) by using a green synthesis method using the aqueous extract from the peels of Citrus reticulata. Both HR-TEM and Fe-SEM analyses have confirmed the flower-like morphology for the synthesised nanoparticles. The observed zeta potential value of −48.0 mV further indicated its highly stable structure. The X-ray diffractogram of the ZnO NFs showed the characteristic diffraction peaks for the crystalline ZnO without any impurity peak, indicating the complete reduction into nanoparticles and thereby, the formation of pure crystalline ZnO NFs. The antibacterial activity of ZnO NFs was then studied using the standard well diffusion method and demonstrated significant bactericidal effects against Staphylococcus aureus and Escherichia coli, with a minimum inhibitory concentration (MIC) of 0.048 mg mL−1. Additionally, the ZnO NFs were evaluated for their potential to enhance the shelf life of Gerbera jamesonii flowers when treated with different concentrations in a chitosan-based solution. The ZnO NFs supplemented solution here was found to preserve the freshness of the cut flowers for up to 9.3 ± 0.3 days compared to the 3-day shelf life of the control group. These findings suggest ZnO NFs to have significant antibacterial properties and can effectively extend the shelf life of cut flowers.

Characterization and Antimicrobial Properties of Zinc Oxide Nanoflakes Prepared Via Green Chemistry Method Using Corn Silk Extract of Zea Mays

AbstractThe pathogen‐based diseases are prime concern for modern society. Some oxide‐based nanomaterials have been found to show promising antimicrobial activities. However, the industrial synthesis of these oxide materials are harmful to environment. Zinc oxide nano‐flakes were prepared using corn silk (Zea mays) extract. The material was characterized by spectral and microscopic techniques. XRD data shows rutile structure and nano‐crystal size of 36.15 nm. SEM indicates morphology consisting of nano size particles with porous structure. EDX confirms presence of Zn and O. UV‐Vis data shows band gap of 3.62 eV. On excitation, PL exhibits a variety of emission bands in visible spectrum. Dielectric properties suggest the dielectric constant has a well‐dispersed real and imaginary portion. The ZnO NFs were subjected to antimicrobial activities (in dark and under white light) against various strains like E. coli, K. pneumonia and S. aureus. The light induced antibacterial activity is slightly higher as compared to that in dark. Best part of this study is that minimum concentration of ZnO can be used in presence of light thereby reducing the toxicity to the environment due to these metal oxides. Based on the observed results, this material could be used as multi‐dimensional functional material in day‐to‐day life.

Screening of low-toxic zinc oxide nanomaterials and study the apoptosis mechanism of NSC-34 cells.

With the increasing application of ZnO nanomaterials (ZnO-NMts) in the biomedical field, it is crucial to assess their potential risks to humans and the environment. Therefore, this study aimed to screen for ZnO-NMts with low toxicity and establish safe exposure limits, and investigate their mechanisms of action. The study synthesized 0D ZnO nanoparticles (ZnO NPs) and 3D ZnO nanoflowers (ZnO Nfs) with different morphologies using a hydrothermal approach for comparative research. The ZnO-NMts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Mouse brain neuronal cells (NSC-34) were incubated with ZnO NMts for 6, 12, and 24h, and the cell morphology was observed using TEM. The toxic effects of ZnO Nfs on NSC-34 cells were studied using CCK-8 cell viability detection, reactive oxygen species (ROS) measurement, caspase-3 activity detection, Annexin V-FITC/PI apoptosis assay, and mitochondrial membrane potential (Δφm) measurement. The results of the research showed that ZnO-NMts caused cytoplasmic vacuolization and nuclear pyknosis. After incubating cells with 12.5µgmL-1 ZnO-NMts for 12h, ZnO NRfs exhibited the least toxicity and ROS levels. Additionally, there was a significant increase in caspase-3 activity, depolarization of mitochondrial membrane potential (Δφm), and the highest rate of early apoptosis.This study successfully identified ZnO NRfs with the lowest toxicity and determined the safe exposure limit to be<12.5µgmL-1 (12h). These findings will contribute to the clinical use of ZnO NRfs with low toxicity and provide a foundation for further research on their potential applications in brain disease treatment.

Chiral electrochemiluminescence for simultaneous enantiomeric detection of aspartic acid and phenylalanine.

The burgeoning interest in rapid, simultaneous multi-target detection has propelled advancements in chiral electrochemiluminescence (ECL) assays. This study presents the design and implementation of a potential-resolved dual-color ECL sensor, engineered for the concurrent detection of aspartic acid (Asp) and phenylalanine (Phe) enantiomers. The sensor array was meticulously constructed by amalgamating anodic chiral ECL probe Ru(phen)2(L-Cys) nanocrystals with cathodic ECL probe ZnO nanoflowers (ZnO NFs). This research explored the potential of executing multianalyte assays via a potential-resolved ECL strategy, contributing to the advancements in the field of chiral ECL assays.

ZnO@Ag-Functionalized Paper-Based Microarray Chip for SERS Detection of Bacteria and Antibacterial and Photocatalytic Inactivation.

Bacterial infections caused by pathogenic microorganisms have become a serious, widespread health concern. Thus, it is essential and required to develop a multifunctional platform that can rapidly and accurately determine bacteria and effectively inhibit or inactivate pathogens. Herein, a microarray SERS chip was successfully synthesized using novel metal/semiconductor composites (ZnO@Ag)-ZnO nanoflowers (ZnO NFs) decorated with Ag nanoparticles (Ag NPs) arrayed on a paper-based chip as a supporting substrate for in situ monitoring and photocatalytic inactivation of pathogenic bacteria. Typical Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Vibrio parahemolyticus were selected as models. Partial least-squares discriminant analysis (PLS-DA) was performed to minimize the dimensionality of SERS spectra data sets and to develop a cost-effective identification model. The classification accuracy was 100, 97.2, and 100% for S. aureus, E. coli, and V. parahemolyticus, respectively. The antimicrobial activity of ZnO@Ag was proved by the microbroth dilution method, and the minimum inhibitory concentrations (MICs) of S. aureus, E. coli, and V. parahemolyticus were 40, 50, and 55 μg/mL, respectively. Meanwhile, it demonstrated remarkable photocatalytic performance under natural sunlight for the inactivation of pathogenic bacteria, and the inactivation rates for S. aureus, E. coli, and V. parahemolyticus were 100, 97.03 and 97.56%, respectively. As a result, the microarray chip not only detected the bacteria with high sensitivity but also confirmed the antibacterial and photocatalytic sterilization properties. Consequently, it offers highly prospective strategies for foodborne diseases caused by pathogenic bacteria.

Statistical analysis of the impact of FeO3 and ZnO nanoparticles on the physicochemical and dielectric performance of monoester-based nanofluids

This article deals with a comparative study of the physicochemical and electrical properties of monoesters of castor oil compared with their counterparts based on FeO3 and ZnO nanoparticles. The results are also compared with those in the literature on triesters, and also with the recommendations of the IEEE C 57.14 standard. The data is analysed statistically using a goodness-of-fit test. The analysis of the viscosity data at 40 °C shows an increase in viscosity. For concentrations of 0.10 wt%, 0.15 wt% and 0.20 wt% these are respectively 5.4%, 9.69%, 12.9% for FeO3 NFs and 7.6%, 9.91% and 12.7% for ZnO NFs. For the same concentrations, the increase in acid number is respectively 3.2%, 2.9%, 2.5% for FeO3 samples and 3.18%, 2.0%, 1.2% for ZnO samples. For the same concentrations, the fire point shows an increment of 4%, 3% and 2% for FeO3 samples and a regression of 8.75%, 6.88% and 5.63% for ZnO samples. As for the breakdown voltage, for the same concentrations we observe respectively an increment of 43%, 27%, 34% for the FeO3. The results show an improvement on partial discharge inception voltage with FeO3 of 24%, 8.13% and 15.21% respectively for the concentrations 0.10 wt%, 0.15 wt% and 0.20 wt%.

Cotton fabric loaded with ZnO nanoflowers as a photocatalytic reactor with promising antibacterial activity against pathogenic E. coli

Nanofinishing is the process by which ultrafine dispersion of nanomaterials is applied to a textile for the development of functionalities. The utilization of nanometal oxides as antimicrobial agents have shown a substantial antimicrobial property in cotton. In the present study, previously synthesized powder containing ZnO nanoflowers (ZnO NFs) was characterized for morphology, surface composition, roughness, and charge using Transmission electron microscopy (TEM), Scanning transmission electron microscopy (STEM), Atomic force microscopy(AFM) and Zeta potential. Optical properties of crystalline ZnO were determined by Photoluminescence (PL), Diffused reflectance Spectroscopy (DRS), and bandgap energy determination. Highly crystalline, ZnO NFs bearing crystal defects and high surface charge were loaded onto the pristine cotton by a dip coating method using Triton X-100 as dispersant and iSys MTX fabric binder. The pristine cotton fabric of 125 g/m2 was nano finished by loading 20,42 and 58 µg/cm2 (1–3 dip cycles) ZnO NFs respectively. The loading of ZnO NFs onto the surface of cotton fabric was confirmed by SEM and used for antibacterial activity against E. coli as a photocatalytic reactor. The prepared samples were irradiated with a UV lamp of λmax = 254 nm (15 min, 30 min, 45 min) and D65 artificial sunlight (60 min, 120 min, 180 min) to investigate their photocatalytic activity against pathogenic E. coli using modified Breed Smear’s method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ZnO NFs@ cotton were determined as 19.53 µg/ml and 39.06 µg/ml respectively after exposure to UV light. After exposure to sunlight MIC and MBC observed were higher i.e. 156.25 µg/ml and 312.5 µg/ml respectively showing lesser activity in sunlight as compared to ionizing UV radiations. To verify the photocatalytic activity, hydroxyl radicals generated by ZnO NFs@ cotton were also determinedtime-resolved PL on exposure to a UV lamp and D65 artificial sunlight. This nano-finished cotton is a promising candidate to be used as a medical textile with high antibacterial activity even after 20 washing cycles with only a 5% decrease in efficiency.

Growth of diazonium-functionalized ZnO nanoflakes on flexible carbon cloth for electrochemical sensing of acetone in the liquid phase.

Simple detection of acetone is indispensable due to its health and environmental concerns. Surface-modified electrodes are promising for the detection of acetone. In the present study, the facile fabrication of ZnO nanoflakes on carbon cloth (CC) is reported. The electrode was fabricated by decorating the CC with ZnO nanoparticles (ZnO NPs), followed by the hydrothermal treatment and modification with diazonium salt using linear sweep voltammetry (LSV) forming ZnO nanoflakes (ZnO NFs) on ZnO NPs/CC. The as-prepared ZnO/CC electrode was used for the detection of acetone at room temperature using cyclic voltammetry. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analyses were used for the chemical and physical characterization of the CC before and after each modification step. The obtained data manifested that ZnO NFs functionalized with diazonium salt increased the roughness of the CC surface, which was advantageous to promote the interaction between CC and acetone target. The modified sensing platform showed excellent performance in terms of the wide working range (0.1-2000 ppm) and low detection limit (0.03 ppm), making it a promising and cost-effective sensor of acetone in the liquid phase.

A High Sensitivity Electrochemical Immunosensor Based on Monoclonal Antibody Coupled Flower-Shaped Nano-ZnO for Detection of Tenuazonic Acid

In this paper, an electrochemical biosensor was established for the high-sensitivity detection of Tenuazonic acid (TeA) in fruits based on the enrichment of flower-shaped nano-ZnO and the specific recognition of immune response. Herein flower-shaped nano-ZnO (ZnO NFs) with a hexagonal wurtzite structure and diameter of 700–800 nm were demonstrated to have the optimal specific surface area and outstanding conductivity, compared with different morphology, sizes, and crystal structures of nano-ZnO. Second, the ZnO NFs were used as carriers for efficiently immobilizing monoclonal antibodies to obtain antibody bioconjugates, which were anchored on the 2-mercaptobenzoic acid-modified gold electrode by amide reaction. In the presence of TeA, the monoclonal antibody could specifically recognize and bind to it, resulting in a decrease in electron transfer ability on the gold electrode surface. Finally, the electrochemical biosensor showed a range from 5 × 10−5 μg/mL to 5 × 10−1 μg/mL with a detection limit of 1.14 × 10−5 μg/mL. Furthermore, it exhibited high selectivity for TeA among other analogs, such as Altenuene (ALT) and Alternariol (AOH). Notably, the proposed strategy could be employed to monitor TeA in tomato and citrus, showing potential application prospects in practical application and commercial value.

Eco-benevolent synthesis of ZnO nanoflowers using Oxalis corniculata leaf extract for potential antimicrobial application in agriculture and cosmeceutical

Facile and eco-friendly approach for the convenient synthesis of inorganic nanomaterials offer tremendous bioactivities which can be exploited in various biomedical applications. Here, we established the simple way to synthesize the zinc oxide nanoflowers (ZnO NFs) using a well-known Ayurvedic herb “Oxalis corniculata”, which act as a potential bio-reducing agent. The present study articulated to promote the surface functionalization of nanoflowers using the bio-reductant reservoir of herbal plant extract. The phytochemical profile of plant extract assessed by HPLC method illustrates the presence of the bioactive reducing agent responsible for the synthesis of ZnO NFs. Also, the identified compound considered to be the most resourceful biomolecule that induced conductive charges to prevent clumping of nanoflowers. The physicochemical characterization of nanoflowers was performed by Uv–vis spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, high resolution transmission electron microscopy, and X-ray diffraction technique. Further, its antimicrobial activity was confirmed against contagious gram positive and negative acne causing bacteria. These synthesized nanoflowers also showed antioxidant activity. Overall, our result demonstrates that these nanoflowers are endowed with valuable bioactive agents and promising great potential for cosmeceutical and agriculture applications.

Phyto-reflexive Zinc Oxide Nano-Flowers synthesis: An advanced photocatalytic degradation and infectious therapy

Combating the limitations of chemical approach, a Phyto-reflexive surface decorated ZnO nanoparticles were synthesis for enhanced activity against resistant infectious agent and toxic dyes. Flower-like ZnO nanostructure with average size of 30 nm and 25 nm using chemical method and Phyto-synthesised respectively. Prepared ZnO nano-flowers have been characterised by UV (UV–visible spectrometry), XRD (X-ray Diffraction), TEM (Transmission Electron Microscopy), HRTEM (High Resolution Transmission Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy). Anti-bacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa , exhibited 78%, 88% inhibition for chemical prepared ZnO NFs and Phyto-reflexive surface modified ZnO NFs exhibited 85%, 94% compared to Ciprofloxacin. MIC (Minimum Inhibitory Concentration) values against S. aureus and P. aeruginosa of biological ZnO NFs, were calculated as 62.5 and 125 ug/ml and 125 and 250 ug/ml for chemically synthesized ZnO NFs respectively. Anti-fungal activity against Aspergillus niger and Candida Albicans showed 78%, 80% activity with chemically ZnO NFs and 91%, 100% inhibition with biologically ZnO NFs. Anti-oxidant potential determination revealed 56.5% and 67.8% activity at 50 mg/mL with chemical and biological ZnO NF respectively. Furthermore, Degradation of methylene blue (MB) using ZnO NFs up to 78% using chemically prepared and 90% using Phyto-reflexive ZnO NFs. Thus, the comparative analysis concluded, Phyto-reflexive surface modified synthesis of ZnO NFs improved infections activity against pathogens and photocatalytic activity for hazardous chemicals.

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.

Functionalization of Zinc Oxide Nanoflowers with Palladium Nanoparticles via Microwave Absorption for Room Temperature-Operating Hydrogen Gas Sensors in the ppb Level.

Microwave-assisted functionalization of zinc oxide nanoflowers (ZnO NFs) with palladium nanoparticles (Pd NPs) is demonstrated to realize high-performance chemiresistive-type hydrogen (H2) gas sensors operating at room temperature (RT). The developed gas sensors exhibit a high response of up to 70% at 50 ppm and a theoretical detection limit of 10 ppb. The formation of ZnO NFs with an enhanced specific surface area and their functionalization with Pd NPs are investigated through various characterizations. Furthermore, the optimization of microwave absorption upon the structural incorporations between nanostructures (NF-NPs) is investigated for solution-based functionalization at low temperatures (below 120 °C) for short process times (within 1 min), compared to the conventional thermal annealing at 250 °C for 1 h. Highly sensitive and selective ZnO-based gas sensors enabling the detection of H2 gas molecules at 300 ppb concentration at RT exhibit a short response/recovery time of below 3 min and a good selectivity toward different gases including nitric oxide, carbon monoxide, and oxygen. The successful functionalization of nanostructured metal oxide semiconductors (MOSs) with metal NPs via effective and practical microwave absorption enhances the potential on highly sensitive and selective chemiresistive-type MOS-based gas sensors operating at RT without additional heaters or photogenerators.

3D self-supporting heterostructure NiCo-LDH/ZnO/CC electrode for flexible high-performance supercapacitor

Two kinds of nanostructured ZnO, namely nanorods (ZnO NR) and nanoflakes (ZnO NF) were first prepared on conductive flexible carbon cloth (CC) by a hydrothermal route. Then nickel cobalt layered double hydroxide (NiCo-LDH) nanoflakes were directly hydrothermally deposited on them to construct three-dimensional (3D) self-supporting heterostructure NiCo-LDH/ZnO NR/CC and NiCo-LDH/ZnO NF/CC flexible electrodes. The effects of different nanostructured ZnO on morphology, structure and electrochemical performance of NiCo-LDH/ZnO/CC composite materials were investigated. It is found that NiCo-LDH nanoflakes grown on ZnO NF/CC substrate are more compact and uniform than those on ZnO NR/CC substrate. Moreover, NiCo-LDH/ZnO NF/CC electrode presents better electrochemical properties than NiCo-LDH/ZnO NR/CC electrode with 2.6 times higher specific capacitance (1577.6 F g−1 at 1 A g−1), 2.2 times better rate capability, and 1.5 time greater cycle stability, which may be attributed to the larger contact area and more redox-active sites provided by the NiCo-LDH NFs grown on ZnO NFs. Furthermore, the as-assembled solid-state flexible NiCo-LDH/ZnO NF//AC (active carbon) asymmetric supercapacitor (ASC) delivers a maximal energy density of 51.39 Wh kg−1 (800 W kg−1) with a high operating window of 1.6 V, and exhibits great cyclic stability with 87.3% capacitance retaining after 1000 cycles, which is higher than many reported ASCs. Finally, two packaged ASCs in series successfully lighted a red light-emitting diode (LED, 2.2 V/20 mA), evincing the potentiality of practical application.

Flexible and Linker-Free Enzymatic Sensors Based on Zinc Oxide Nanoflakes for Noninvasive L-Lactate Sensing in Sweat

We report on a highly sensitive, selective, and flexible enzymatic sensor based on Zinc oxide nanoflakes (ZnO NFs) for noninvasive L-lactate sensing in sweat. A single step sonochemical process was used to synthesize ZnO NFs on gold-coated flexible polyethylene terephthalate (PET) substrates. The lactate oxidase enzyme (LOx) immobilized on the as-synthesized ZnO-NFs-based sensing electrode provided a high level of selectivity for lactate sensing. The sensor was tested in the range of 10 pM–20 mM, which covers the entire physiological range and demonstrated the sensitivity of $11.76~\mu \text{A}$ /decade/cm2 and the limit of detection (LoD) of 1.26 nM. The presented sensor does not require a linker due to the high isoelectric point of ZnO-NFs yet demonstrated ~55 times better response compared to conventional gold electrodes with a linker. Our statistical analysis showed that the sensor also has high reproducibility.

AgInSe2-Sensitized ZnO Nanoflower Wide-Spectrum Response Photoelectrochemical/Visual Sensing Platform via Au@Nanorod-Anchored CeO2 Octahedron Regulated Signal.

Herein an ultrasensitive photoelectrochemical (PEC)/visual biosensor coupled with a multiple signal amplification strategy was proposed for the detection of nucleic acids. The initial signal amplification was achieved via ternary AgInSe2 quantum dot (QD)-sensitized ZnO nanoflowers (ZnO NFs) to form an excellent photoelectric layer. A gold-modified nanorod-anchored CeO2 (Au@NR-CeO2) octahedron was introduced as a multifunctional signal regulator via the formation of triple helix molecules. The Au@NR-CeO2 octahedron could not only quench the photocurrent signal due to the competitive capture of photon energy and electron donors with the photoelectric layer but could also act like a peroxidase to catalyze the formation of mimetic enzymatic catalytic precipitation (MECP) on the surface of the photoelectric layer. Furthermore, the steric hindrance effect from the Au@NR-CeO2 octahedron further reduced the output of the photocurrent signal. After incubation with t-DNA, the triple helix conformation was disassembled and the Au@NR-CeO2 octahedron was released from the electrode surface, leading to the significant increase of photocurrent signal. Meanwhile, the released Au@NR-CeO2 octahedron could flow into the colorimetric area of the lab-on-paper device to catalyze the occurrence of the color reaction, achieving a visual detection for t-DNA. On the basis of the multiple signal amplification strategy, t-DNA was detected specifically with a lower limit of detection of 0.28 fM and a wider linear range from 0.5 fM to 50 nM. The proposed method has the potential utility to detect a variety of nucleic acids and biomarkers.

Facile Fabrication of ZnO Nanofibers Based Photoanode for Cost Effective Metal–Free Organic Dye–Sensitized Solar Cells

A facile substrate grown method was employed to fabricate zinc oxide nanofibers (ZnO Nfs) modified photoanode on fluorine-doped tin oxide (FTO) substrate. The modified ZnO Nfs photoanode was used to fabricate dye sensitized solar cell (DSSC), sensitized with a cheap metal free organic dye, eosin yellow (eosin-Y). The efficiency of solar to electrical energy conversion was achieved as 1.51% with simulated AM 1.5 G solar irradiation of 100 mW cm−2 . The better efficiency is ascribed to the effective diffusion of electrons within the one dimensional (1D) ZnO Nfs and the efficient interfacial contact between the electrolyte and the ZnO photoanode through pinholes and pores present in the twisted nanofibers. These facilitated the improved interfacial charge transfer. The result demonstrates the promising route of substrate grown ZnO nanofibers for the application of photoanode material in DSSCs.