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Amperometric response of 3D porous ZnO–CuO HNCs (10, 15, 20, and 25 min) electrodes as well as 3D mixed ZnO/CuO, 3D pure CuO and ZnO NWs electrodes at an applied potential of 0.7 V upon successive additions of different concentration of glucose in a step of 10, 50, and 200 μM, respectively for each current step, inset is the current response of 3D porous ZnO–CuO HNCs (20 min) to 0.47 and 1 μM glucose). (b) The corresponding calibration curve of current vs. concentration of glucose. The error bars denote the standard deviation of triplicate determination of each concentration of glucose.
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Three-dimensional (3D) porous ZnO-CuO hierarchical nanocomposites (HNCs) nonenzymatic glucose electrodes with different thicknesses were fabricated by coelectrospinning and compared with 3D mixed ZnO/CuO nanowires (NWs) and pure CuO NWs electrodes. The structural characterization revealed that the ZnO-CuO HNCs were composed of the ZnO and CuO mixed...
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... 3D structure can effectively accelerate the electron transfer. In addition, The CV measurement of 3D porous ZnO-CuO HNCs (20 min) electrode was further performed in 0.1 M NaOH solution at different scan rates (Fig. 7). The peak current shows a linear response to the scan rate, implying a surface-controlled elec- trochemical process 7 . Fig. 8a shows the I-t curve of different 3D electrodes performed at 10.7 V (vs. Ag/AgCl) in 0.1 M NaOH solution by addition of dif- ferent concentration of glucose. It is clear that well-defined and fast amperometric responses are observed, except the pure ZnO NWs electrode which also has no response to glucose in I-t curve. The average times ...
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... calibration curve of 3D electrodes is shown in Fig. 8b and the corresponding sensitivity, correlation coefficient, linear range, and detection limit under a signal/noise ratio of 3 are summarized in Table 1. As is compared, the 3D porous ZnO-CuO HNCs electrode (20 min) exhibits the best glucose biosensing performance in this work, which has the highest sensitivity of 3066.4 mAmM 21 cm 22 , ...
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... Table 1. As is compared, the 3D porous ZnO-CuO HNCs electrode (20 min) exhibits the best glucose biosensing performance in this work, which has the highest sensitivity of 3066.4 mAmM 21 cm 22 , larger linear range from 0.47 mM to 1.6 mM, and the lower practical detection limit of 0.21 mM according to actual measurement data (as shown in inset of Fig. 8a). For the response time of the sensor for 0.47 mM glucose is calculated to be about 5.5, this is because low concentration of glucose need longer time to spread to the electro- desurface, which leads to the response time increased, compared with that to 200 mM ...
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In this work, the Cux@Ni100−x core–shell nanoparticles (CSNPs) are deposited on reduced graphene oxide (rGO) sheets, and this nanocomposites (in a Nafion matrix) are shown to be a viable materials for nonenzymatic sensing of glucose. A novel nonenzymatic glucose sensor based on a glass carbon electrode modified with Cu53@Ni47 CSNPs/rGO (referred to...
Citations
... Fig. 2 displays the XRD spectra of pure and doped CuO-ZnO samples with different concentrations of antimony (Sb). The samples exhibit precise indexing corresponding to a combination of monoclinic CuO (indexed to JCPDS 48-1548) and hexagonal ZnO (indexed to JCPDS 36-1451) [37]. Besides, the insertion of Sb dopant with different concentrations (2.5% and 5%) effectively influenced the XRD spectra of the sample. ...
This study involves the synthesis of CuO–ZnO nanocomposites with varying Sb doping levels (0%, 2.5%, and 5%) through a facile sol-gel process. Structural analysis via X-ray diffraction confirmed the presence of ZnO’s hexagonal wurtzite phase and CuO’s monoclinic phase in all samples, indicating reduced crystallinity due to doping. The average crystallite size was determined using Scherrer’s formula, revealing a decrease in size with doping (33 nm, 31 nm, and 30 nm for 0%, 2.5%, and 5% Sb, respectively). Morphology and chemical composition were assessed using field emission scanning electron microscopy, and energy dispersive X-ray analysis. The optical bandgap of the Sb-doped CuO–ZnO nanocomposites was determined using a Tauc plot, resulting in values of 2.48 eV, 2.39 eV, and 2.32 eV for dopant concentrations of 0%, 2.5%, and 5%, respectively. Dielectric permittivity and tangent loss were studied across the frequency range of 100 Hz to 1 MHz at different temperatures ranging from 303 K to 723 K measured between 100 Hz and 1 MHz frequency, revealing Maxwell- Wagner-type interfacial polarization. The dielectric permittivity data reveal anomalous behavior near 673 K, shifting with doping, and is explained by thermal ionization and relaxation mechanisms. The ac conductivity, which varies with frequency, demonstrates low-frequency dispersion and is effectively described by Jonscher’s power law aligned with the dielectric analysis. Magneto-dielectric measurements showed a positive effect for permittivity and a negative effect for tangent loss, which may be caused by the changes in dipole alignment. The magneto-dielectric effect was further explored by analyzing the impact of magnetic fields (0–1.5 T) on impedance spectroscopy. Nyquist plots obtained at various magnetic fields were fitted using parallel combinations of resistance-capacitor circuits. These plots were then employed to estimate the contributions of both grains and grain boundaries. Overall, the findings from this study provide a foundation for the development of multifunctional materials with tailored properties for a wide range of optoelectronic devices.
... Despite a limited linear detection range, the electrospinning method employed for electrode fabrication ensured reproducibility and stability. The superior sensing performance was attributed to the three-dimensional porous morphology, providing a high surface area [168]. ...
The wide array of structures and characteristics found in ZnO-based nanostructures offers them a versatile range of uses. Over the past decade, significant attention has been drawn to the possible applications of these materials in the biomedical field, owing to their distinctive electronic, optical, catalytic, and antimicrobial attributes, alongside their exceptional biocompatibility and surface chemistry. With environmental degradation and an aging population contributing to escalating healthcare needs and costs, particularly in developing nations, there's a growing demand for more effective and affordable biomedical devices with innovative functionalities. This review delves into particular essential facets of different synthetic approaches (chemical and green) that contribute to the production of effective multifunctional nano-ZnO particles for biomedical applications. Outlining the conjugation of ZnO nanoparticles highlights the enhancement of biomedical capacity while lowering toxicity. Additionally, recent progress in the study of ZnO-based nano-biomaterials tailored for biomedical purposes is explored, including biosensing, bioimaging, tissue regeneration, drug delivery, as well as vaccines and immunotherapy. The final section focuses on nano-ZnO par-ticles' toxicity mechanism with special emphasis to their neurotoxic potential, as well as the primary toxicity pathways, providing an overall review of the up-to-date development and future perspectives of nano-ZnO particles in the biomedicine field.
... Nanoparticles in electrochemical sensing structures can serve a variety of functions, such as catalyzing electrochemical reactions, increasing the transfer of electrons, tagging, and acting as a reactant. Electrochemical biosensors that were primarily based on the enzyme after doing more studies enzymes appear to be naturally unstable and are susceptible to denaturation in harsh environments, which limits the lifetime of biosensors and thus their usefulness [64]. As a result, non-enzymatic electrochemical biosensors are required. ...
... For ZnO nanostructures, no current can be noticed for either of the cases ( Fig. 6a and b). In the absence of glucose, although C 2 shows no current response, C 50 demonstrates a very minor reduction peak at 0.6 V, caused by Cu(II)/Cu(III) redox couple [39]. Upon the addition of 0.6 mM glucose, both C 2 and C 50 display a catalytic current. ...
The present study investigates the non-enzymatic glucose sensing properties of Cu
O–ZnO (x = 1,2) composite nanostructures that have been fabricated using a simple and fast co-electrodeposition (CED) method. Two concentrations of Cu
were used and interestingly, for the lower concentration, the fabricated (C
) nanostructures are of Cu
O–ZnO type while for the higher concentration (C
), nanostructures show a mixed Cu
O–ZnO (x = 1,2) nature. Although both the samples exhibit a good catalytic response for non-enzymatic glucose sensing, the C
sample shows a far superior response. Along with a high sensitivity of 384.6 µA mM
cm
, a large linear range of 0.03–3 mM, and a low least detection limit (LOD) of 0.7 µM, C
also demonstrates a good long-term stability, good reproducibility, and good selectivity toward glucose detection, even in the presence of interfering species. The synergistic effect of Cu
O–ZnO composite nanostructures and their semiconducting nature may be contributing to the good response of C
as a glucose sensor. The results presented here demonstrate that C
can be an excellent non-enzymetic glucose sensor for measuring glucose in blood and food samples
... One of the common examples is glucose, which is significant in modifying a variety of biological processes [92]. To achieve sensitive glucose detection [93] and to provide an effective platform for glucose monitoring, several types of nanofibers have been combined with glucose oxidase [94] or functional nanomaterials (such as semiconducting oxides) [95]. Numerous applications need the precise and sensitive identification of proteins. ...
... Enzyme-free sensors used for the determination of ascorbic acid levels, which are of practical importance in both food processing and medical diagnostics [33][34][35][36][37], have attracted much research attention due to their high reproducibility and stability compared to enzyme-based sensors. However, since most enzyme-free sensors used for ascorbic acid rely on the chemical activity of the transition metal center, which can be easily altered, the fabrication of enzyme-free sensor elements for ascorbic acid detection with high performance remains a challenge [38]. The efficiency of sensors is evaluated using many parameters, such as speed, high sensitivity, stability, and operating voltage. ...
Information on vitamin C—ascorbic acid (AA)—content is important as it facilitates the provision of dietary advice and strategies for the prevention and treatment of conditions associated with AA deficiency or excess. The methods of determining AA content include chromatographic techniques, spectrophotometry, and electrochemical methods of analysis. In the present work, an electrochemical enzyme-free ascorbic acid sensor for a neutral medium has been developed. The sensor is based on zinc oxide nanowire (ZnO NW) arrays synthesized via low-temperature chemical deposition (Chemical Bath Deposition) on the surface of an ITO substrate. The sensitivity of the electrochemical enzyme-free sensor was found to be dependent on the process treatments. The AA sensitivity values measured in a neutral PBS electrolyte were found to be 73, 44, and 92 µA mM−1 cm−2 for the ZnO NW-based sensors of the pristine, air-annealed (AT), and air-annealed followed by hydrogen plasma treatment (AT+PT), respectively. The simple H-plasma treatment of ZnO nanowire arrays synthesized via low-temperature chemical deposition has been shown to be an effective process step to produce an enzyme-free sensor for biological molecules in a neutral electrolyte for applications in health care and biomedical safety.
... Glucose serves as one of the classic examples. To obtain sensitive glucose detection, many kinds of nanofibers have been combined with glucose oxidase or useful nanomaterials (such as semiconducting oxides), offering a reliable platform for glucose monitoring [10][11][12]. Today, a variety of applications and circumstances necessitate the precise detection and quantification of a variety of distinct analytes. The use of biosensors for precise and sensitive detection of proteins, point-of-care testing (POC), the detection of food and environmental toxins, biological warfare agents, illegal narcotics, and the identification of human and animal disease indicators has revolutionized Sensors 2023, 23, 6705 3 of 29 diagnostics [13][14][15][16][17][18]. ...
The present review article discusses the elementary concepts of the sensor mechanism and various types of materials used for sensor applications. The electrospinning method is the most comfortable method to prepare the device-like structure by means of forming from the fiber structure. Though there are various materials available for sensors, the important factor is to incorporate the functional group on the surface of the materials. The post-modification sanction enhances the efficiency of the sensor materials. This article also describes the various types of materials applied to chemical and biosensor applications. The chemical sensor parts include acetone, ethanol, ammonia, and CO2, H2O2, and NO2 molecules; meanwhile, the biosensor takes on glucose, uric acid, and cholesterol molecules. The above materials have to be sensed for a healthier lifestyle for humans and other living organisms. The prescribed review articles give a detailed report on the electro spun materials for sensor applications.
... The 3D ZnO/CuO nanoheterostructure has a high specific surface area and p-n junction between p-CuO and n-ZnO, leading to improved light absorption and low charge recombination [5,[18][19][20][21]. Therefore, this material is considered suitable for a wide range of practical applications, such as sensors [22][23][24], photocatalysts [18,21,[25][26][27][28], and photoelectrodes [5,8,19,20,29,30]. ZnO/CuO heterojunction branched NWs show promise for PEC hydrogen (H 2 ) generation [8]. ...
... Owing to the incomplete reactions between acid chloride (O=C-Cl) groups on PACMC-TMC and secondary amine (-NH-) groups on PIP, a number of O=C-Cl groups stayed intact during acylation and were hydrolyzed to form carboxylic acid (O=C-O) groups subsequently, with assigned peaks at 286.4 eV (C-O) and 288.6 eV (O=C-O) [35,36]. Moreover, in O 1s core level spectra, the peaks of O=C-O (532.0 eV), C-OH (532.9 eV) and OH (533.7 eV) were observed in Fig. S1d, which were generated during the hydrolysis reaction and can be attributed to the dissociated oxygen/OH groups on the membranes [37][38][39]. Moreover, the N-C=O groups at 531.1 eV indicate the successful construction of polyamide membranes through the IP reaction [40]. ...
Water permeability and ion sieving ability are the main indicators that determine the separation performance of nanofiltration membranes. Enlarging surface areas of permeable separation layers is an effective pathway to facilitate water flux while maintaining salt retention. Inspired by the condensation and cross-linking of amino groups/imines with acid chlorides to form dense polyamide networks, we proposed a strategy to enlarge separation surface areas of nanofiltration membranes by grafting highly porous por-phyrin-aniline conjugated microporous polymers (PACMP) onto polyamide. Upon forming CMP-polyamide composite membranes via one-step interfacial polymerization, an ultra-permeable composite membrane (61.8 L m −2 h −1) was fabricated , with salt (Na2SO4) rejection rate above 91.6%. Besides, thanks to the reactive oxygen species produced by porphyrin groups of PACMPs, the in situ generated photoexcited singlet oxygen (1O2) can kill 98.5% of Escherichia coli and 99.7% of Staphylococcus aureus, imparting excellent antibacterial properties to the CMP-polyamide composite membranes.
... Hence, it is critical to comprehend the mechanism of the selectivity of ZnO-based sensors without the existence of the enzyme. It was reported that ZnO-CuO, ZnO-NiO, and ZnO-Ni (OH)2modified electrodes showed reasonable selectivity to various electroactive molecules, including ascorbic acid, L-aspartic acid, dopamine, and uric acid [102,103,104,105] thus, the sensor selectivity is guided by electrostatic repulsion interaction. It is worth noting that, in selectivity analysis of the nonenzymatic biosensors, the percent of glucose to intrusive molecules is mostly 10: 1, taking into account that the blood glucose level is at least 30 times larger than those of the intrusive particles [104,106,107]. ...
In the last few decades’ electrochemical biosensors have witnessed vast developments due to the broad range of different applications, including health care and medical diagnosis, environmental monitoring and assessment, food industry, and drug delivery. Integration of nanostructured material with different disciplines and expertise of electrochemistry, solid-state physics, material science, and biology has offered the opportunity of a future generation of highly rapid, sensitive, stable, selective, and novel electrochemical biosensor devices. Among metal oxide nanomaterials, ZnO nanostructures are one of the most important nanomaterials in today’s nanotechnology research. Such nanostructures have been studied intensely not only for their extraordinary structural, optical, and electronic properties but also for their prominent performance in diverse novel applications such as photonics, optics, electronics, drug delivery, cancer treatment, bio-imaging, etc. However, functionality of these nanomaterials is eventually dictated by the capability to govern their properties including shape, size, position, and crystalline structure on the nanosized scale. This review aims to update the outstanding advancement in the developments of the enzymatic and non-enzymatic biosensors using a different structure of ZnO nanomaterials. After a coverage of the basic principles of electrochemical biosensors, we highlight the basic features of ZnO as a potential anticancer agent. focused attention gives to functionalized biosensors based on ZnO nanostructures for detecting biological analytes, such as glucose, cholesterol, L-lactic acid, uric acid, metal ions, and pH.
