Ni/CdS Bifunctional Ti@TiO2 Core–Shell Nanowire Electrode for High-Performance Nonenzymatic Glucose Sensing

Multifunctional tunable Cu2O and CuInS2 quantum dots on TiO2 nanotubes for efficient chemical oxidation of cholesterol and ibuprofen

In this study, a CuInS2/Cu2O/TiO2 nanotube (TNT) heterojunction-based hybrid material is reported for the selective detection of cholesterol and ibuprofen. Anodic TNTs were co-decorated with Cu2O and CuInS2 quantum dots (QDs) using a modified chemical bath deposition (CBD) method. QDs help trigger the chemical oxidation of cholesterol by cathodically generating hydroxyl radicals (˙OH). The small size of QDs can be used to tune the energy levels of electrode materials to the effective redox potential of redox species, resulting in highly improved sensing characteristics. Under optimal conditions, CuInS2/Cu2O/TNTs show the highest sensitivity (∼12 530 μA mM-1 cm-2, i.e. up to 11-fold increase compared to pristine TNTs) for cholesterol detection with a low detection limit (0.013 μM) and a fast response time (1.3 s). The proposed biosensor was successfully employed for the detection of cholesterol in real blood samples. In addition, fast (4 s) and reliable detection of ibuprofen (with a sensitivity of ∼1293 μA mM-1 cm-2) as a water contaminant was achieved using CuInS2/Cu2O/TNTs. The long-term stability and favourable reproducibility of CuInS2/Cu2O/TNTs illustrate a unique concept for the rational design of a stable and high-performance multi-purpose electrochemical sensor.

Current advancements and prospects of enzymatic and non-enzymatic electrochemical glucose sensors

This review discusses the most current developments and future perspectives in enzymatic and non-enzymatic glucose sensors, which have notably evolved over the preceding quadrennial period. Furthermore, a thorough exploration encompassed the sensor's intricate fabrication processes, the diverse range of materials employed, the underlying principles of detection, and an in-depth assessment of the sensors' efficacy in detecting glucose levels within essential bodily fluids such as human blood serums, urine, saliva, and interstitial fluids. It is worth noting that the accurate quantification of glucose concentrations within human blood has been effectively achieved by utilizing classical enzymatic sensors harmoniously integrated with optical and electrochemical transduction mechanisms. Monitoring glucose levels in various mediums has attracted exceptional attention from industrial to academic researchers for diabetes management, food quality control, clinical medicine, and bioprocess inspection. There has been an enormous demand for the creation of novel glucose sensors over the past ten years. Research has primarily concentrated on succeeding biocompatible and enhanced sensing abilities related to the present technologies, offering innovative avenues for more effective glucose sensors. Recent developments in wearable optical and electrochemical sensors with low cost, high stability, point-of-care testing, and online tracking of glucose concentration levels in biological fluids can aid in managing and controlling diabetes globally. New nanomaterials and biomolecules that can be used in electrochemical sensor systems to identify glucose concentration levels are developed thanks to advances in nanoscience and nanotechnology. Both enzymatic and non-enzymatic glucose electrochemical sensors have garnered much interest recently and have made significant strides in detecting glucose levels. In this review, we summarise several categories of non-enzymatic glucose sensor materials, including composites, non-precious transition metals and their metal oxides, hydroxides, precious metals and their alloys, carbon-based materials, conducting polymers, metal-organic framework (MOF)-based electrocatalysts, and wearable device-based glucose sensors deeply.

Combining quasi-ZIF-67 hybrid nanozyme and G-quadruplex/hemin DNAzyme for highly sensitive electrochemical sensing

Zeolitic imidazolate frameworks (ZIFs), a famous subfamily of metal-organic frameworks (MOFs), are considered promising electrocatalysts. Herein, ZIF-67 was selected as an electrocatalyst for designing electrochemical sensors due to having the best electrocatalytic activity in ZIFs. To overcome the insufficient electrocatalytic activity of ZIFs, ZIF-67 derivatives (QZIF-67-X, where X represents calcination time) were obtained by calcining at 250 °C for a certain time. The porous structure of the precursor in QZIF-67-X is maintained, exposing more active centers. QZIF-67-X could accelerate electron transfer and lead to improve the electrocatalytic performance. Moreover, QZIF-67-2 was chosen as an Au nanoparticle-supported nanocarrier to further bind G-quadruplex/hemin DNAzymes with strong catalytic activity due to the best supporting activity of QZIF-67-2 among QZIF-67-X. The synergistic catalysis of QZIF-67-2 and G-quadruplex/hemin DNAzymes effectively amplified the reduction current signal of H₂O₂. The linear range of the prepared electrochemical sensor was 2 μM-65 mM, and the detection limit was 1.2 μM. Moreover, the real-time detection of H₂O₂ from HepG2 cells was achieved by the sensor, providing a novel technique for efficient anticancer drug evaluation. These results suggested that QZIF-67 can be utilized as an efficient electrocatalyst for improving the sensitivity of sensors.

CdS-Modified TiO2 Nanotubes with Heterojunction Structure: A Photoelectrochemical Sensor for Glutathione

The formation of heterojunction structures can effectively prevent the recombination of photogenerated electron-hole pairs in semiconductors and result in the enhancement of photoelectric properties. Using TiO₂ nanotubes (prepared using the hydrothermal-impregnation method) as carriers, CdS-TiO₂NTs were fabricated as a photoelectrochemical (PEC) sensor, which can be used under visible light and can exhibit good PEC performance due to the existence of the heterojunction structure. The experimental results show that the prepared CdS-TiO₂NTs electrode had a linear response to 2-16 mM glutathione (GSH). The sensor's sensitivity and detection limit (LOD) were 102.9 µA·mM^-1 cm^-2 and 27.7 µM, respectively. Moreover, the biosensor had good stability, indicating the potential application of this kind of heterojunction PEC biosensor.

Electrochemical Sensor Made with 3D Micro-/Mesoporous Structures of CoNi-N/GaN for Noninvasive Detection of Glucose

Noninvasive detection of glucose (NGD) is important because ∼10% of the global population is suffering from diabetes. Herein, a three-dimensional (3D) micro-/mesoporous structure, i.e., a CoNi-N nanosheet-coated GaN 3D scaffold (CoNi-N@GaN-3S), was proposed for detecting saliva glucose, where the GaN scaffold can provide a large open surface for nanosheet decoration, while the catalytic nanosheets can increase the surface area and prevent the GaN-3S from anodic corrosion. Moreover, it was found that high-temperature ammoniation of CoNi can lead to dense atomic holes and an N-terminated surface (CoNi-N), which promoted the ionization of CoNi with a higher catalytic activity. It is the first time that dense atomic holes have been observed in CoNi to our knowledge. The designed CoNi-N@GaN-3S sensor was applied to the electrochemical detection of glucose with a low limit of detection (LOD) of 60 nM and a high sensitivity, selectivity, and stability. In addition, detection of human-saliva glucose was realized with an LOD of 5 μM, which was more than 4-fold lower than reported reliable LODs. An integrated sensor with a low consumption of saliva sample was demonstrated for NGD.

Nanowire-based sensor electronics for chemical and biological applications

Detection and recognition of chemical and biological species via sensor electronics are important not only for various sensing applications but also for fundamental scientific understanding. In the past two decades, sensor devices using one-dimensional (1D) nanowires have emerged as promising and powerful platforms for electrical detection of chemical species and biologically relevant molecules due to their superior sensing performance, long-term stability, and ultra-low power consumption. This paper presents a comprehensive overview of the recent progress and achievements in 1D nanowire synthesis, working principles of nanowire-based sensors, and the applications of nanowire-based sensor electronics in chemical and biological analytes detection and recognition. In addition, some critical issues that hinder the practical applications of 1D nanowire-based sensor electronics, including device reproducibility and selectivity, stability, and power consumption, will be highlighted. Finally, challenges, perspectives, and opportunities for developing advanced and innovative nanowire-based sensor electronics in chemical and biological applications are featured.

Dark-field microscopic real-time monitoring the growth of Au on Cu2O nanocubes for ultra-sensitive glucose detection

Nanoparticle plasmon scattering can provide real-time imaging information on the formation process of noble metal-based nanomaterials. Due to the synergistic effect of the interface between metal and oxide supporting pores, metal nanoparticles (NPs), especially Au NPs, generally exhibit higher catalytic activity on oxide carriers than single-component NPs. Here, we use the dark field scattering microscope to in situ monitor the growth of Au on Cu₂O surface by oxidation-reduction reactions and the nanostructures could be precisely controlled via the scattering signal. The prepared Cu₂O/Au nanocomposite has a higher electrocatalytic activity toward Glucose. When being used as a potential biosensor for nonenzyme glucose detection, excellent performance, such as high sensitivity with a detection limit of 4 μM, high selectivity and outstanding stability, was obtained. The scattering imaging strategy is a convenient and universal approach in controllable synthesis of plasmonic heterostructures, and leads to the improvement of electrocatalysts in biosensing.

Mesoporous TiO2-based architectures as promising sensing materials towards next-generation biosensing applications

In the past two decades, mesoporous TiO2 has emerged as a promising material for biosensing applications. In particular, mesoporous TiO2 materials with uniform, well-organized pores and high surface areas typically exhibit superior biosensing performance, which includes high sensitivity, broad linear response, low detection limit, good reproducibility, and high specificity. Therefore, the development of biosensors based on mesoporous TiO2 has significantly intensified in recent years. In this review, the expansion and advancement of mesoporous TiO2-based biosensors for glucose detection, hydrogen peroxide detection, alpha-fetoprotein detection, immobilization of enzymes, proteins, and bacteria, cholesterol detection, pancreatic cancer detection, detection of DNA damage, kanamycin detection, hypoxanthine detection, and dichlorvos detection are summarized. Finally, the future perspective and research outlook on the utilization of mesoporous TiO2-based biosensors for the practical diagnosis of diseases and detection of hazardous substances are also given.

Voltage-Switchable Biosensor with Gold Nanoparticles on TiO2 Nanotubes Decorated with CdS Quantum Dots for the Detection of Cholesterol and H2O2

A thin layer of gold nanoparticles (Au NPs) sputtered on cadmium sulfide quantum dots (CdS QDs) decorated anodic titanium dioxide nanotubes (TNTs) (Au/CdS QDs/TNTs) was fabricated and explored for the nonenzymatic detection of cholesterol and hydrogen peroxide (H₂O₂). Morphological studies of the sensor revealed the formation of uniform nanotubes decorated with a homogeneously dispersed CdS QDs and Au NPs layer. The electrochemical measurements showed an enhanced electrocatalytic performance with a fast electron transfer (∼2 s) between the redox centers of each analyte and electrode surface. The hybrid nanostructure (Au/CdS QDs/TNTs) electrode exhibited about a 6-fold increase in sensitivity for both cholesterol (10,790 μA mM^-1 cm^-2) and H₂O₂ (78,833 μA mM^-1 cm^-2) in analyses compared to the pristine samples. The hybrid electrode utilized different operational potentials for both analytes, which may lead to a voltage-switchable dual-analyte biosensor with a higher selectivity. The biosensor also demonstrated a good reproducibility, thermal stability, and increased shelf life. In addition, the clinical significance of the biosensor was tested for cholesterol and H₂O₂ in real blood samples, which showed maximum relative standard deviations of 1.8 and 2.3%, respectively. These results indicate that a Au/CdS QDs/TNTs-based hybrid nanostructure is a promising choice for an enzyme-free biosensor due to its suitable band gap alignment and higher electrocatalytic activities.

One-Step Electrodeposition of Silver Nanostructures on 2D/3D Metal-Organic Framework ZIF-67: Comparison and Application in Electrochemical Detection of Hydrogen Peroxide

Metal-organic frameworks (MOFs) have been widely used as supporting materials to load or encapsulate metal nanoparticles for electrochemical sensing. Herein, the influences of morphology on the electrocatalytic activity of Co-containing zeolite imidazolate framework-67 (ZIF-67) as supporting materials were studied. Three types of morphologies of MOF ZIF-67 were facilely synthesized by changing the solvent because of the influence of the polar solvent on the nucleation and preferential crystal growth. Two-dimensional (2D) ZIF-67 with microplate morphology and 2D ultrathin ZIF-67 nanosheets were obtained from pure H₂O (H-ZIF-67) and a mixed solution of dimethylformamide and H₂O (D-ZIF-67), respectively. Three-dimensional ZIF-67 with rhombic dodecahedron morphology was obtained from pure methanol (M-ZIF-67). Then, one-step electrodeposition of silver nanostructures on ZIF-67-modified glassy carbon electrode (Ag/ZIF-67/GCE) was performed for the reduction of hydrogen peroxide (H₂O₂). Cyclic voltammetry can be used to investigate the electrocatalytic activity of Ag/ZIF-67/GCE, and Ag/H-ZIF-67/GCE displayed the best electrocatalytic property than Ag/D-ZIF-67/GCE and Ag/M-ZIF-67/GCE. The electrochemical H₂O₂ sensor showed two wide linear ranges of 5 μM to 7 mM and 7 to 67 mM with the sensitivities of 421.4 and 337.7 μA mM^-1 cm^-2 and a low detection limit of 1.1 μM. In addition, the sensor exhibited good selectivity, high reproducibility, and stability. Furthermore, it has been utilized for real-time detection of H₂O₂ from HepG2 human liver cancer cells. This work provides a novel strategy for enhancing the detection performance of electrochemical sensors by changing the crystalline morphologies of supporting materials.

Laser-induced graphene hybrid photoelectrode for enhanced photoelectrochemical detection of glucose

The combination of an electrocatalyst with a semiconductor light absorber is of great importance to increase the efficiency of photoelectrochemical (PEC) glucose detection. Here, in situ and synchronous fabrication of a Ni-based electrocatalyst (NiEC) and CdS semiconductor in laser-induced graphene (LIG) on indium-tin oxide glass is demonstrated via a one-step laser-induced solid phase transition. A series of component and structural characterization experiments suggest that the laser-induced NiEC uniformly disperses in the hybrid nanocomposite and exists mainly in the Ni⁰ and NiO states. Moreover, both electrochemical and PEC investigations confirm that the as-prepared hybrid photoelectrode exhibits excellent photoelectrocatalytic ability towards glucose, which is not only attributed to the strong synergistic interaction between CdS and NiEC, but also benefited from the high conductivity as well as 3D macroporous configuration of the simultaneously formed LIG, providing the key factor to achieve sensitive non-enzymatic PEC glucose sensors. Therefore, the laser-induced hybrid photoelectrode is then applied to the PEC detection of glucose, and a low detection limit of 0.4 μM is obtained with good stability, reproducibility, and selectivity. This study provides a promising paradigm for the facile and binder-free fabrication of an electrocatalyst-semiconductor-graphene hybrid photoelectrode, which will find potential applications in sensitive PEC biosensing for a broad range of analytes.

Constructing a TiO2/PDA core/shell nanorod array electrode as a highly sensitive and stable photoelectrochemical glucose biosensor

Developing stable PEC glucose biosensors with high sensitivity and low detection limit is highly desirable in the biosensor field. Herein, a highly stable and sensitive enzymatic glucose photoelectrochemical biosensor is rationally designed and fabricated by constructing TiO₂/PDA core/shell nanorod arrays. The TiO₂ nanorod as the core has the advantages of increasing charge transportation towards interfaces and enhancing the absorption of incident sunlight due to its single-crystal nature and one dimensional array structure. The PDA shell not only induces a rapid charge transfer across the interfaces but also stabilizes the biosensor performance by avoiding the decomposition of enzymes induced by the strong oxidizing holes from the TiO₂ core. A remarkable performance with an ultrahigh sensitivity of 57.72 μA mM⁻¹ cm⁻², a linear range of 0.2–1.0 mM, a glucose detection limit of 0.0285 mM (S/N = 3) and a high sensitivity of 8.75 μA mM⁻¹ cm⁻² in a dynamic range of 1.0–6.0 mM were obtained for the glucose detection. This study might provide a strategy for constructing inorganic/organic core/shell structures with a satisfactory PEC performance.

Developing stable PEC glucose biosensors with high sensitivity and low detection limit is highly desirable in the biosensor field.

Construction of ZnO/ZIF-9 heterojunction photocatalyst: enhanced photocatalytic performance and mechanistic insight

Heterostructure construction in photocatalysts is an effective method to improve their catalytic activity because of the remarkable role that the heterostructure plays in charge separation.

Fabrication of porous NiMn2O4 nanosheet arrays on nickel foam as an advanced sensor material for non-enzymatic glucose detection

In this work, porous NiMn₂O₄ nanosheet arrays on nickel foam (NiMn₂O₄ NSs@NF) was successfully fabricated by a simple hydrothermal step followed by a heat treatment. Porous NiMn₂O₄ NSs@NF is directly used as a sensor electrode for electrochemical detecting glucose. The NiMn₂O₄ nanosheet arrays are uniformly grown and packed on nickel foam to forming sensor electrode. The porous NiMn₂O₄ NSs@NF electrode not only provides the abundant accessible active sites and the effective ion-transport pathways, but also offers the efficient electron transport pathways for the electrochemical catalytic reaction by the high conductive nickel foam. This synergy effect endows porous NiMn₂O₄ NSs@NF with excellent electrochemical behaviors for glucose detection. The electrochemical measurements are used to investigate the performances of glucose detection. Porous NiMn₂O₄ NSs@NF for detecting glucose exhibits the high sensitivity of 12.2 mA mM⁻¹ cm⁻² at the window concentrations of 0.99–67.30 μM (correlation coefficient = 0.9982) and 12.3 mA mM⁻¹ cm⁻² at the window concentrations of 0.115–0.661 mM (correlation coefficient = 0.9908). In addition, porous NiMn₂O₄ NSs@NF also exhibits a fast response of 2 s and a low LOD of 0.24 µM. The combination of porous NiMn₂O₄ nanosheet arrays and nickel foam is a meaningful strategy to fabricate high performance non-enzymatic glucose sensor. These excellent properties reveal its potential application in the clinical detection of glucose.

Nitrogen-containing three-dimensional biomass porous carbon materials as an efficient enzymatic biosensing platform for glucose sensing

Schematic illustration of the fabrication and structure of the 3D-CVS/GOD electrode.

Phase transformation synthesis of TiO2/CdS heterojunction film with high visible-light photoelectrochemical activity

CdS/TiO₂ heterojunction film used as a photoanode has attracted much attention in the past few years due to its good visible light photocatalytic activity. However, CdS/TiO₂ films prepared by conventional methods (successive ionic layer adsorption and reaction, chemical bath deposition and electrodeposition) show numerous grain boundaries in the CdS layer and an imperfect contact at the heterojunction interface. In this study, we designed a phase transformation method to fabricate CdS/TiO₂ nanorod heterojunction films. The characterization results showed that the CdS layer with fewer grain boundaries was conformally coated on the TiO₂ nanorod surface and the formation mechanism has been explained in this manuscript. Moreover, the prepared CdS/TiO₂ films show a high photocatalytic activity and the photocurrent density is as high as 9.65 mA cm^-2 at 0.80 V versus RHE. It may be attributed to fewer grain boundaries and a compact heterojunction contact, which can effectively improve charge separation and transportation.

Twin-mediated epitaxial growth of highly lattice-mismatched Cu/Ag core-shell nanowires

Lattice-mismatch is an important factor for the heteroepitaxial growth of core-shell nanostructures. A large lattice-mismatch usually leads to a non-coherent interface or a polycrystalline shell layer. In this study, a conformal Ag layer is coated on Cu nanowires with dense nanoscale twin boundaries through a galvanic replacement reaction. Despite a large lattice mismatch between Ag and Cu (∼12.6%), the Ag shell replicates the twinning structure in Cu nanowires and grows epitaxially on the nanotwinned Cu nanowire. A twin-mediated growth mechanism is proposed to explain the epitaxy of high lattice-mismatch bimetallic systems in which the misfit dislocations are accommodated by coherent twin boundaries.

One-step synthesis of novel Cu@polymer nanocomposites through a self-activated route and their application as nonenzymatic glucose sensors

Novel core–shell Cu@polymer nanocomposites were synthesized through a one-step self-activated route and developed as nonenzymatic glucose sensor.

A hydrothermally grown CdS nanograin-sensitized 1D Zr:α-Fe2O3/FTO photoanode for efficient solar-light-driven photoelectrochemical performance

A CdS nanograin sensitized 1D Zr:Fe₂O₃ nanorod arrays nanostructure was hydrothermally synthesized and showed an excellent photoelectrochemical performance due to the combined effect of light absorption in CdS and effective charge transport in one dimensional Zr:Fe₂O₃ nanorod arrays.

Cu2+1O/graphene nanosheets supported on three dimensional copper foam for sensitive and efficient non-enzymatic detection of glucose

Three dimensional copper foam/Cu₂₊₁O/graphene nanosheets for sensitive and efficient non-enzymatic detection of glucose.

Negative differential resistance in GeSi core-shell transport junctions: the role of local sp(2) hybridization

We report a theoretical investigation of nonlinear quantum transport properties of Au/GeSi/Au junctions. For GeSi semiconducting core-shell structures brought into contact with Au electrodes, a very unusual behavior is that the tunneling transport is on-resonance right at equilibrium. This resonance is not due to the alignment of a quantum level in GeSi to the electrochemical potential of Au, but due to the alignment of very sharp DOS features - hot spots, localized at the two Au/GeSi interfaces of the device. An applied bias voltage shifts the hot spots relative to each other which gives rise to substantial negative differential resistance (NDR). The hot spots localized at the two interfaces were found to be due to the unbonded pz orbital of a sp(2) hybridized interface Si atom which is surrounded by three non-sp(2) hybridized neighbors. The mechanism of inducing hot spots and NDR by a local structure unit is not limited to the GeSi. The results suggest an interesting scheme for constructing NDR devices by orbital manipulation, to be more explicit, for example, by designing local structural units having unbonded orbitals at the interfaces between electrodes and the central region of the transport junction.

Hierarchical 3-dimensional nickel-iron nanosheet arrays on carbon fiber paper as a novel electrode for non-enzymatic glucose sensing

Three-dimensional nickel-iron (3-D/Ni-Fe) nanostructures are exciting candidates for various applications because they produce more reaction-active sites than 1-D and 2-D nanostructured materials and exhibit attractive optical, electrical and catalytic properties. In this work, freestanding 3-D/Ni-Fe interconnected hierarchical nanosheets, hierarchical nanospheres, and porous nanospheres are directly grown on a flexible carbon fiber paper (CFP) substrate by a single-step hydrothermal process. Among the nanostructures, 3-D/Ni-Fe interconnected hierarchical nanosheets show excellent electrochemical properties because of its high conductivity, large specific active surface area, and mesopores on its walls (vide infra). The 3-D/Ni-Fe hierarchical nanosheet array modified CFP substrate is further explored as a novel electrode for electrochemical non-enzymatic glucose sensor application. The 3-D/Ni-Fe hierarchical nanosheet arrays exhibit significant catalytic activity towards the electrochemical oxidation of glucose, as compared to the 3-D/Ni-Fe hierarchical nanospheres, and porous nanospheres. The 3-D/Ni-Fe hierarchical nanosheet arrays can access a large amount of glucose molecules on their surface (mesopore walls) for an efficient electrocatalytic oxidation process. Moreover, 3-D/Ni-Fe hierarchical nanosheet arrays showed higher sensitivity (7.90 μA μM(-1) cm(-2)) with wide linear glucose concentration ranging from 0.05 μM to 0.2 mM, and the low detection limit (LOD) of 0.031 μM (S/N = 3) is achieved by the amperometry method. Further, the 3-D/Ni-Fe hierarchical nanosheet array modified CFP electrode can be demonstrated to have excellent selectivity towards the detection of glucose in the presence of 500-fold excess of major important interferents. All these results indicate that 3-D/Ni-Fe hierarchical nanosheet arrays are promising candidates for non-enzymatic glucose sensing.

Sensitive colorimetric detection of glucose and cholesterol by using Au@Ag core–shell nanoparticles

Sensitive colorimetric detection of glucose and cholesterol by using Au@Ag core–shell nanoparticles.

Nonenzymatic Glucose Biosensors Based on Silver Nanoparticles Deposited on TiO2Nanotubes

In the present research, a nonenzymatic glucose biosensor was fabricated by depositing Ag nanoparticles (Ag-NPs) using in situ chemical reduction method on TiO2nanotubes which were synthesized by anodic oxidation process. The structure, morphology, and mechanical behaviors of electrode were examined by scanning electron microscopy and nanoindentation. It was found that Ag-NPs remained both inside and outside of TiO2nanotubes whose length and diameter were about 1.2 μm and 120 nm. The composition was constructed as an electrode of nonenzymatic biosensor for glucose oxidation. The electrocatalytic properties of the prepared electrodes for glucose oxidation were investigated by cyclic voltammetry (CVs) and differential pulse voltammetry (DPV). Compared with bare TiO2and Ag-fresh TiO2nanotube, Ag-TiO2/(500°C) nanotube exhibited the best electrochemical properties from cyclic voltammetry (CVs) results. Differential pulse voltammetry (DPV) results showed that, at +0.03 V, the sensitivity of the electrode to glucose oxidation was3.69 mA⁎cm-2⁎mM-1with a linear range from 20 mM to 190 mM and detection limit of 24 μM (signal-to-voice ratio of 3). In addition the nonenzymatic glucose sensors exhibited excellent selectivity, stability, and repeatability.

Sensitive electrochemical nonenzymatic glucose sensing based on anodized CuO nanowires on three-dimensional porous copper foam

In this work, we proposed to utilize three-dimensional porous copper foam (CF) as conductive substrate and precursor of in-situ growth CuO nanowires (NWs) for fabricating electrochemical nonenzymatic glucose sensors. The CF supplied high surface area due to its unique three-dimensional porous foam structure, and thus resulted in high sensitivity for glucose detection. The CuO NWs/CF based nonenzymatic sensors presented reliable selectivity, good repeatability, reproducibility, and stability. In addition, the CuO NWs/CF based nonenzymatic sensors have been employed for practical applications, and the glucose concentration in human serum was measured to be 4.96 ± 0.06 mM, agreed well with the value measured from the commercial available glucose sensor in hospital, and the glucose concentration in saliva was also estimated to be 0.91 ± 0.04 mM, which indicated that the CuO NWs/CF owned the possibility for noninvasive glucose detection. The rational design of CuO NWs/CF provided an efficient strategy for fabricating of electrochemical nonenzymatic biosensors.

Three-Dimensional Cu Foam-Supported Single Crystalline Mesoporous Cu2O Nanothorn Arrays for Ultra-Highly Sensitive and Efficient Nonenzymatic Detection of Glucose

Highly sensitive and efficient biosensors play a crucial role in clinical, environmental, industrial, and agricultural applications, and tremendous efforts have been dedicated to advanced electrode materials with superior electrochemical activities and low cost. Here, we report a three-dimensional binder-free Cu foam-supported Cu2O nanothorn array electrode developed via facile electrochemistry. The nanothorns growing in situ along the specific direction of <011> have single crystalline features and a mesoporous surface. When being used as a potential biosensor for nonenzyme glucose detection, the hybrid electrode exhibits multistage linear detection ranges with ultrahigh sensitivities (maximum of 97.9 mA mM(-1) cm(-2)) and an ultralow detection limit of 5 nM. Furthermore, the electrode presents outstanding selectivity and stability toward glucose detection. The distinguished performances endow this novel electrode with powerful reliability for analyzing human serum samples. These unprecedented sensing characteristics could be ascribed to the synergistic action of superior electrochemical catalytic activity of nanothorn arrays with dramatically enhanced surface area and intimate contact between the active material (Cu2O) and current collector (Cu foam), concurrently supplying good conductivity for electron/ion transport during glucose biosensing. Significantly, our findings could guide the fabrication of new metal oxide nanostructures with well-organized morphologies and unique properties as well as low materials cost.