Electrochemical nonenzymatic sensing of glucose using advanced nanomaterials

A Non-enzymatic Electrochemical Sensor for Glucose Detection Based on Ag@TiO2@ Metal-Organic Framework (ZIF-67) Nanocomposite

This work presents the preparation of an efficient and sensitive glucose sensor for the detection of glucose in an alkaline media. The glucose sensor is composed of a metal organic framework (MOF) composite comprising Ag@TiO₂ nanoparticles. The hybrid of Ag@TiO₂ encapsulated in ZIF-67 was synthesized by the solvothermal method and applied onto a glassy carbon electrode (GCE) for the non-enzymatic sensing of glucose. The porosity of ZIF-67 was favorable for the unhindered diffusion and entrapment of glucose and its cavities served as reaction vessels. The electrochemical behavior of Ag@TiO₂@ZIF-67 showed amplified results when compared with that of Ag@TiO₂ and ZIF-67. Cyclic tests toward the oxidation of glucose has demonstrated excellent stability of a MOF-based hybrid sensor. The sensor based on Ag@TiO₂@ZIF-67 showed high sensitivity of 0.788 μAμM⁻¹cm⁻² with a linear concentration range of 48 μM⁻¹ mM and a response time of 5 s with an excellent detection limit of 0.99 μM (S/N = 3).

Electrochemical Oxidation of Monosaccharides at Nanoporous Gold with Controlled Atomic Surface Orientation and Non-Enzymatic Galactose Sensing

Non-enzymatic saccharide sensors are of great interest in diagnostics, but their non-selectivity limits their practical diagnostic abilities. In this study, we investigated the electrochemical oxidation of monosaccharides at nanoporous gold (NPG) catalysts with different contributions of surface crystallographic orientations. Fructose elicited no clear electrochemical response, but glucose, galactose, and mannose produced clear oxidative current. The onset potentials for oxidation of these saccharides depended on the surface atomic structure of the NPG. The oxidation potential was approximately 100 mV less positive at the Au(100)-enhanced NPG than at the Au(111)-enhanced NPG. Furthermore, the voltammetric responses significantly differed among the saccharides. Galactose was oxidized at less positive potential and exhibited a higher current response than the other saccharides. This tendency was enhanced in the presence of chloride ions. These features enabled the selective and sensitive detection of galactose at an NPG electrode without enzymes under physiological conditions. A linear range of 10 μM to 1.8 mM was obtained in the calibration plot, which was comparable to those in previously reported enzymatic galactose sensors. Thus, we demonstrated that controlling the crystallographic orientation on the nanostructured electrode surface is useful in developing electrochemical sensors.

Highly branched gold-copper nanostructures for non-enzymatic specific detection of glucose and hydrogen peroxide

The development of highly sensitive and highly selective sensors for non-enzymatic glucose and hydrogen peroxide (H₂O₂) detection using gold-copper alloy nanoparticles (AuCu alloy NPs) is reported. The AuCu NPs are nanostructures with branches and can be used as an electrochemical catalyst. Series of AuCu alloy NPs with various metal ratios are synthesized through a coreduction reaction. The morphology of AuCu alloy NPs is altered from highly branched structures (nanourchin, nanobramble, nanostar, nanocrystal) to a spherical shape by increasing Au content in the synthesis reaction. Cu-rich AuCu nanobramble and Au-rich AuCu nanostar exhibit selective electrocatalysis behaviors toward electro-oxidation of glucose and electroreduction of H₂O₂, respectively. The AuCu nanobramble-based sensor holds great potential in glucose detection with a linear working range of 0.25 to 10 mM. The sensor possesses a sensitivity of 339.35 μA mM^-1 cm^-2, a limit of detection (LOD) of 16.62 μM, which is an acceptable selectivity and good stability. In addition, the AuCu nanostar-based sensor shows excellent electrochemical responses toward H₂O₂ reduction with good selectivity, reproducibility, and a short response time of about 2-3 s. The linear range for H₂O₂ determination is 0.05 to 10 mM, with LOD and sensitivity of 10.93 μM and 133.74 μA mM^-1 cm^-2, respectively. The good sensing performance is a result of the synergistic surface structure and atomic composition effects, which leads AuCu alloys to be a promising nanocatalyst for sensing both glucose and H₂O₂. Graphical abstract Schematic illustration presents the construction of gold-copper alloy nanoparticles (AuCu alloy NPs) on the surface of screen-printed carbon electrode (SPCE). The highly branched nanostructures of AuCu alloys with different surface structure and metal ratios give selective electrocatalysis behaviors. Cu-rich AuCu nanobramble-based sensor reveals prominent electrocatalytic activity for glucose detection. Au-rich AuCu nanostar-based sensor provides good electrochemical response for H₂O₂ detection.

Facile preparation of novel Pd nanowire networks on a polyaniline hydrogel for sensitive determination of glucose

In this study, novel Pd nanowire networks (PdNW) grown on three-dimensional polyaniline hydrogel (3D-PANI) were prepared via a facile one-step electrodeposition approach at a constant potential of - 0.2 V and further utilized as an electrochemical sensing material for sensitive determination of glucose in alkaline medium. Compared with the sensor based on Pd nanofilm (PdNF)/3D-PANI prepared by electrodeposition at - 0.9 V, the sensor based on PdNW/3D-PANI presented substantially enhanced electrocatalytic activity towards glucose oxidation, with an excellent sensitivity of 146.6 μA mM^-1 cm^-2, a linear range from 5.0 to 9800 μM, and a low detection limit of 0.7 μM and was, therefore, demonstrated to be available for the determination of glucose in human serum. These findings are likely attributed to the combination of advantages of both PdNW and 3D-PANI, which outperformed most other Pd-based non-enzymatic glucose sensors reported earlier. Moreover, this non-enzymatic electrochemical sensor based on PdNW/3D-PANI may serve as an alternative tool for the assay of glucose and possibly other biomolecules. Graphical abstract.

An Electrochemical Non-Enzymatic Glucose Sensor Based on Ultrathin PdAg Single-Crystalline Nanowires

Electrochemical non-enzymatic sensors have great potential for prompt and efficient detection of glucose. Herein, a novel, highly efficient electrochemical non-enzymatic glucose sensor is reported that is based on ultrathin PdAg single-crystalline nanowires (NWs). Ultrathin PdAg NWs are fabricated by a facile one-pot aqueous synthesis through an in situ growth strategy with an amphiphilic surfactant as the template. A comparison of the activities of PdAg NWs with different compositional ratios and nanostructures shows that ultrathin Pd₂ Ag₁ NWs hold the best performance toward electrochemical detection of glucose with an operable sensitivity of 11.6 μA mM^-1  cm^-2 and a linear response range of 0.1-8 mM. Structural and compositional features of the Pd₂ Ag₁ NWs allow an excellent selectivity, rapid response, and good long-term stability for electrochemical glucose sensor. This work thus provides a new possibility for the rational design and synthesis of noble-metal-based nanomaterials for non-enzymatic sensors.

Cobalt-copper bimetallic nanostructures prepared by glancing angle deposition for non-enzymatic voltammetric determination of glucose

A bimetallic nanostructure of Co/Cu for the non-enzymatic determination of glucose is presented. The heterostructure includes cobalt thin film on a porous array of Cu nanocolumns. Glancing angle deposition (GLAD) method was used to grow Cu nanocolumns directly on a fluorine-doped tin oxide (FTO) substrate. Then a thin film of cobalt was electrodeposited on the Cu nanostructures. Various characterization studies were performed in order to define the optimum nanostructure for the determination of glucose. The results showed remarkable boosting of the electrocatalytic activity of Co/Cu bimetallic structure compare to the responses achieved by the monometallic structures of Co or Cu. The sensor showed two linear response ranges for the determination of glucose at 0.55 V in 0.1 M NaOH, from 5 μM-1 mM and 2-9 mM. The sensitivity was 1741 (μA mM^-1 cm^-2) and 626 (μA mM^-1 cm^-2), respectively, while the detection limit for a signal-to-noise ratio of 3 was found to be 0.4 μM. The sensor exhibited excellent selectivity and was successfully applied to the determination of glucose in real human blood serum samples. Graphical Abstract Schematic representation of fabrication process of the glucose sensor of Co (Cobalt)/Cu (Copper) on Fluorine doped Tin Oxide (FTO). The current voltage plots show higher electrooxidation activity of the bimetallic nanostructure of Co/Cu/FTO relative to the bare Co/FTO.

Nanostructured nickel oxide electrodes for non-enzymatic electrochemical glucose sensing

Nanostructured nickel (Ni) and nickel oxide (NiO) electrodes were fabricated on Ni foils using the glancing angle deposition (GLAD) technique. Cyclic voltammetry and amperometry showed the electrodes enable non-enzymatic electrochemical determination of glucose in strongly alkaline media. Under optimized conditions of NaOH concentration and working potential (~ 0.50 V vs. Ag/AgCl), the GLAD electrodes performed far better than bare Ni foil electrodes, with the GLAD NiO electrode showing an outstanding sensitivity (4400 μA mM^-1 cm^-2), superior detection limit (7 nM), and wide dynamic range (0.5 μM-9 mM), with desirable selectivity and reproducibility. Based on their performance at a low concentration, the GLAD NiO electrodes were also used to quantify glucose in artificial urine and sweat samples which have significantly lower glucose levels than blood. The GLAD NiO electrodes showed negligible response to the common interferents in glucose measurement (uric acid, dopamine, serotonin, and ascorbic acid), and they were not poisoned by high amounts of sodium chloride. Graphical abstract The figures depict (A) SEM image of vertical post-GLAD NiO electrodes used for non-enzymatic electrochemical glucose monitoring, and (B) calibration plots of the three different electrodes.

A buckypaper decorated with CoP/Co for nonenzymatic amperometric sensing of glucose

A freestanding and flexible buckypaper modfied with CoP/Co (CoP/Co-BP) is described. It has a sponge-like nanostructure and is shown to enable improved nonenzymatic sensing of glucose. The CoP/Co-BP was prepared by first depositing a uniform layer of ZIF- 67 crystals on BP, followed by two steps of pyrolysis treatment and phosphidation under an argon atmosphere. The morphology and structure of the material were characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The electrochemical properties were investigated by cyclic voltammetry and amperometric response. The amperometric sensor, best operated at 0.45 V (vs. SCE) at pH 13 has a linear range that extends from 0.5 μM to 1.8 mM of glucose, a 0.2 μM detection limit (at S/N = 3), and a sensitivity of 6427 μA mM^-1 cm^-2 in alkaline solution. This is mainly attributed to the synergistic effect between the highly active CoP nanostructure and BP which results in excellent conductivity. The uniformly distributed CoP nanoparticles in the network of BP prevent the formation of close-packed structure and facilitate electron transfer. The sensor has good selectivity and excellent long-term stability. It was applied to the determination of glucose in spiked human serum, and satisfactory results were obtained. Graphical abstractSchematic presentation of a freestanding and flexible buckypaper modfied with CoP/Co. It has a sponge-like nanostructure and exhibits improved catalytic activity toward glucose oxidation. This material was used for high-performance electrochemical glucose sensing.

A nickel-cobalt bimetallic phosphide nanocage as an efficient electrocatalyst for nonenzymatic sensing of glucose

The authors describe Ni-Co bimetal phosphide (NiCoP) nanocages that exhibit enhanced electrocatalytic performance toward glucose oxidation. The nanocages offer an appealing architecture, large specific area, and good accessibility for the analyte glucose. When placed on a glassy carbon electrode, the sensor exhibits attractive figures of merit for sensing glucose in 0.1 M NaOH solution including (a) a wide linear range (0.005-7 mM), (b) a low determination limit (0.36 μM), (c) high sensitivity (6115 μA•μM^-1•cm^-2), (d) a relatively low working potential (0.50 V vs. Ag/AgCl), and (e) good selectivity, reproducibility, and stability. The sensor is successfully applied to the determination of glucose in human serum samples. Graphical abstractSchematic representation of a glassy carbon electrode modified with Ni-Co bimetal phosphide (NiCoP) nanocage. NiCoP nanocage exhibits excellent electrocatalytic activity toward glucose oxidation. NiCoP nanocage is applied in a sensitive non-enzymatic glucose sensor.

Synthesis of porous Co3S4 for enhanced voltammetric nonenzymatic determination of glucose

Porous Co₃S₄ was synthesized by a two-step hydrothermal method, and its morphology and structure were characterized by transmission electron microscopy and X-ray diffraction. Electrochemical investigations showed that a glassy carbon electrode modified with Co₃S₄ exhibits high electrocatalytic activity toward glucose in 0.2 M NaOH solution. Figures of merit for this sensor include (i) a wide linear range (2.0 μM to 1.1 mM), (ii) a working potential near 0.52 V (vs. Ag/AgCl), (iii) high sensitivity (346.7 μA mM^-1 cm^-2), and (iv) a 0.17 μM detection limit. Graphical abstractPorous Co₃S₄ was explored as electrocatalyst for glucose oxidation. It exhibits distinctly higher electrocatalytic activity toward glucose oxidation than Co₃O₄.

Tunable hierarchical surfaces of CuO derived from metal–organic frameworks for non-enzymatic glucose sensing

A facile thermal treatment is conducted to prepare nanosphere stacking CuO derived from Cu-MOF, which achieves good glucose sensing performance and is expected to be effective for developing non-enzyme and non-invasive glucose sensors.

MOF-derived ZnCo2O4 porous micro-rice with enhanced electro-catalytic activity for the oxygen evolution reaction and glucose oxidation

A porous ZnCo₂O₄ micro-rice like microstructure was synthesized via calcination of a Zn–Co MOF precursor at an appropriate temperature. The as-prepared ZnCo₂O₄ sample presented good electrocatalytic oxygen evolution reaction performance with a small overpotential (η₁₀ = 389 mV) and high stability in basic electrolyte. Furthermore, in basic medium, the as-synthesized ZnCo₂O₄ micro-rice also showed good electrocatalytic activity for glucose oxidation. A ZnCo₂O₄ micro-rice modified glass carbon electrode may be used as a potential non-enzymatic glucose sensor. The excellent electrocatalytic OER and glucose oxidation performances of ZnCo₂O₄ might be attributed to the unique porous structure formed by the nanoparticles. The porous architecture of the micro-rice can provide a large number of electrocatalytically active sites and high electrochemical surface area (ECSA). The result may offer a new way to prepare low-cost and high performance oxygen evolution reaction and glucose oxidation electrocatalysts.

A porous ZnCo₂O₄ micro-rice like microstructure was synthesized via calcination of a Zn–Co MOF precursor at an appropriate temperature.

Macro-/meso-porous NiCo2O4 synthesized by template-free solution combustion to enhance the performance of a nonenzymatic amperometric glucose sensor

A sensitive nonenzymatic amperometric glucose sensor is described that relies on a glassy carbon electrode modified with a macro-/meso-porous NiCo₂O₄. NiCo₂O₄ with spinel structure has been prepared via a one-step solution combustion method. The material was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen absorption/desorption. An electrode was coated with the porous material and then displayed excellent electrocatalytic activity towards the direct oxidation of glucose in 0.15 M NaOH solution by cyclic voltammetry. Amperometric I-t curve demonstrated a sensitivity of 2100 μA·mM^-1·cm^-2 at an applied potential of 0.45 V (vs Hg/HgCl). The sensor has a linear response in the 0.001 to 1.0 mΜ glucose concentration range, a fast response time (3.9 s) and a low detection limit (0.38 μΜ). Graphical abstract.

Phytic acid doped poly(3,4-ethylenedioxythiophene) modified with copper nanoparticles for enzymeless amperometric sensing of glucose

A nanocomposite consisting of phytic acid (PA) that was doped with poly(3,4-ethylenedioxy-thiophene) (PEDOT) and modified with copper nanoparticles (CuNPs) was placed on a glassy carbon electrode and then applied in an enzymeless glucose sensor. The undulating PEDOT/PA composite has good conductivity and a large surface area, which was suitable as substrate for the uniform growth of CuNPs. The modified electrode typically operated at a potential near 0.55 V (vs. Ag/AgCl) demonstrated remarkable catalytic activity towards direct oxidation of glucose in NaOH solution (the major limitation of this sensor). Figures of merit include (a) a wide analytical range (5 to 403 μM); (b) high sensitivity (79.27 μA·μM^-1·cm^-2), (c) a low detection limit (0.28 μM at a signal to noise ratio of 3), and (d) fast response (< 4 s). Graphical abstractA nanocomposite of phytic acid (PA) doped poly(3,4-ethylenedioxy-thiophene) (PEDOT) modified with copper nanoparticles (CuNPs) onto a glassy carbon electrode was prepared by electrochemical strategy. The CuNPs/PEDOT/PA-modified electrodes were applied in enzymeless glucose sensors with high performance.

Carbon fibers coated with urchin-like copper sulfide for nonenzymatic voltammetric sensing of glucose

Urchin-like CuS was grown on xanthan gum-derived carbon nanofibers to obtain a sensor for enzyme-free electrochemical sensing of glucose. The unique nanostructure of the sensor provides a large specific surface, more electrocatalytically active sites, and high electrical conductivity. The voltammetric response to glucose, best measured at around 57 mV (vs. Ag/AgCl (E/V)) in 0.1 M NaOH solution, covers two linear ranges, one from 0.1-125 μM, another from 0.16 to 1.2 mM. The sensitivity is quite high (23.7 μA mM^-1 cm^-2), and the detection limit is low (19 nM at S/N = 3). The sensor has high selectivity against potentially interfering molecules such as fructose, appreciable operational stability, excellent durability, and good repeatability (with relative standard deviations of 2.3%). It was successfully applied to the determination of glucose in diluted serum samples. Graphical abstractSchematic representation of electrochemical detection of glucose based on the use of a screen printed carbon electrode (SPCE) modified with CuS and xanthan gum-derived carbon nanofibers (XGCNFs).

A review on recent advancements in electrochemical biosensing using carbonaceous nanomaterials

This review, with 201 references, describes the recent advancement in the application of carbonaceous nanomaterials as highly conductive platforms in electrochemical biosensing. The electrochemical biosensing is described in introduction by classifying biosensors into catalytic-based and affinity-based biosensors and statistically demonstrates the most recent published works in each category. The introduction is followed by sections on electrochemical biosensors configurations and common carbonaceous nanomaterials applied in electrochemical biosensing, including graphene and its derivatives, carbon nanotubes, mesoporous carbon, carbon nanofibers and carbon nanospheres. In the following sections, carbonaceous catalytic-based and affinity-based biosensors are discussed in detail. In the category of catalytic-based biosensors, a comparison between enzymatic biosensors and non-enzymatic electrochemical sensors is carried out. Regarding the affinity-based biosensors, scholarly articles related to biological elements such as antibodies, deoxyribonucleic acids (DNAs) and aptamers are discussed in separate sections. The last section discusses recent advancements in carbonaceous screen-printed electrodes as a growing field in electrochemical biosensing. Tables are presented that give an overview on the diversity of analytes, type of materials and the sensors performance. Ultimately, general considerations, challenges and future perspectives in this field of science are discussed. Recent findings suggest that interests towards 2D nanostructured electrodes based on graphene and its derivatives are still growing in the field of electrochemical biosensing. That is because of their exceptional electrical conductivity, active surface area and more convenient production methods compared to carbon nanotubes. Graphical abstract Schematic representation of carbonaceous nanomaterials used in electrochemical biosensing. The content is classified into non-enzymatic sensors and affinity/ catalytic biosensors. Recent publications are tabulated and compared, considering materials, target, limit of detection and linear range of detection.

Molecular Design of a New Diboronic Acid for the Electrohydrodynamic Monitoring of Glucose

A new dicationic diboronic acid structure, DBA2+, was designed to exhibit good affinity (K_d ≈1 mm) and selectivity toward glucose. Binding of DBA2+ to glucose changes the pK_a of DBA2+ from 9.4 to 6.3, enabling opportunities for detection of glucose at physiological pH. Proton release from DBA2+ is firmly related to glucose concentrations within the physiologically relevant range (0-30 mm), as verified by conductimetric monitoring. Negligible interference from other sugars (for example, maltose, fructose, sucrose, lactose, and galactose) was observed. These results demonstrate the potential of DBA2+ for selective, quantitative glucose sensing. The nonenzymatic strategy based on electrohydrodynamic effects may enable the development of stable, accurate, and continuous glucose monitoring platforms.

Novel bimetallic Cu/Ni core-shell NPs and nitrogen doped GQDs composites applied in glucose in vitro detection

In present work, a highly sensitive biosensor with high selectivity for glucose monitoring is developed based on novel nano-composites of nitrogen doped graphene quantum dots (N-GQDs) and a novel bimetallic Cu/Ni core-shell nanoparticles (CSNPs) (Cu@Ni CSNPs/N-GQDs NCs). With the tuned electronic properties, N-GQDs helped bimetallic core-shell structure nanomaterials from aggregation, and separate the charges generated at the interface. This novel nano-composites also have the good electrical conductivity of N-GQDs, catalyst property of Cu/Ni bimetallic nano composite, Cu@Ni core-shell structure and the synergistic effect of the interaction between bimetallic nano composite and N-GQDs. While modified the electrode with this novel nano-composites, the sensor' linear range is 0.09 ~ 1 mM, and the limit of detection (LOD) is 1.5 μM (S/N = 3) with a high sensitivity of 660 μA mM-1 cm-2, and rapid response time (3 s). Its' LOD is more than 74 times lower than the traditional Cu@Ni CSNPs modified working electrode. It also has higher sensitivity and wider linear range. This indicates the great potential of applying this kind of nano composites in electrode modification.

A non-enzymatic amperometric glucose sensor based on the use of graphene frameworks-promoted ultrafine platinum nanoparticles

Ultrafine platinum nanoparticles are grown on a 3D graphene framework (GF-Pt) via a hydrothermal method. The material, when placed on a glassy carbon electrode (GCE), displays enhanced electrocatalytic activity towards glucose oxidation. This is assumed to be the result of the numerous easily accessible active sites, an enlarged electrochemically active area, and the presence of multiple electron/ion transport channels. The modified GCE can be operated at a low potential (- 0.15 V vs. Ag/AgCl) has linear responses in the 0.1 μM - 0.01 mM and 0.01 mM - 20 mM glucose concentration range, and a 30 nM detection limit. It was applied to the rapid determination of glucose in human serum samples. Graphical abstract Schematic presentation of a glassy carbon electrode modified with ultrafine Pt nanoparticles grown on a graphene framework (GFs-Pt). GFs-Pt presents enhanced electrocatalytic activity towards glucose oxidation. GFs-Pt is used in a sensitive non-enzymatic amperometric glucose sensor.

Bifunctional and highly sensitive electrochemical non-enzymatic glucose and hydrogen peroxide biosensor based on NiCo2O4 nanoflowers decorated 3D nitrogen doped holey graphene hydrogel

In this work, a simple strategy for fabricating a 3D nitrogen doped holey graphene hydrogel decorated with NiCo₂O₄ nanoflowers (NHGH/NiCo₂O₄) via a one-pot hydrothermal method with subsequent calcination is reported for the first time. The novel NHGH/NiCo₂O₄ nanocomposites featured high electrical conductivity, large and accessible surface areas, abundant active sites, and excellent electrocatalytic performance. Considering the excellent catalytic activity of NiCo₂O₄, a sensitive and bifunctional electrochemical non-enzymatic biosensor was established for the determination of glucose and hydrogen peroxide (H₂O₂). The obtained biosensor exhibited wide linear ranges (glucose: 0.005-10.95 mM; H₂O₂: 1-510 μM) and a low detection limits (glucose: 0.39 μM; H₂O₂: 0.136 μM) in alkaline solution (S/N = 3). Excellent electrocatalytic activity of this sensor was ascribed to the synergistic effects of the hybrid structure between the NiCo₂O₄ nanoflowers and NHGH. Furthermore, the sensitive biosensor also exhibited high selectivity and could be applied to determine glucose in real blood samples. Taken together, the results reveal that the proposed hybrid nanocomposite could be a promising electrochemical biosensor.

A nanocomposite prepared from magnetite nanoparticles, polyaniline and carboxy-modified graphene oxide for non-enzymatic sensing of glucose

The authors report on the synthesis of carboxy functionalized graphene oxide (fGO) decorated with magnetite (Fe₃O₄) nanoparticles. The resulting nanomaterial was used to prepare a composite with polyaniline (PANI) which was characterized by UV-vis, Fourier transform-infrared and Raman spectroscopies. Its surface morphologies were characterized by atomic force and scanning electron microscopies. A screen-printed carbon electrode was then modified with the nanocomposite to obtain an enzyme-free glucose sensor. The large surface of fGO and Fe₃O₄ along with the enhanced charge transfer capability of PANI warrant a pronounced electrochemical response (typically measured at 0.18 V versus Ag/AgCl) which is suppressed in the presence of glucose. This reduction of current by glucose was used to design a sensitive method for quantification of glucose. The response of the modified SPCE is linear in the 0.05 μM - 5 mM glucose concentration range, and the lower detection limit is 0.01 μM. Graphical abstract Schematic illustration of in-situ anchoring of Iron oxide on functionalized graphene oxide and synthesis of its polymeric nanocomposite for non-enzymatic detection of Glucose. The nanocomposite modified screen printed interface enabled monitoring of glucose at lower potential with higher precision. GO (graphene oxide), fGO (functionalized graphene oxide), PANI (polyaniline).

Non-enzymatic fluorescent glucose sensor using vertically aligned ZnO nanotubes grown by a one-step, seedless hydrothermal method

A sensitive non-enzymatic fluorescent glucose sensor, consisting of vertically aligned ZnO nanotubes (NTs) grown on low-cost printed circuit board substrates, is described. The ZnO NTs were synthesized by a one-step hydrothermal method without using a seed layer. The sensor function is based on the photoluminescence (PL) quenching of ZnO NTs treated with different concentrations of glucose. The UV emission (emission maximum at 384 nm under 325 nm excitation) decreases linearly with increasing glucose concentration. The sensor exhibits a sensitivity of 3.5%·mM^-1 (defined as percentage change of the PL peak intensity per mM) and a lower limit of detection (LOD) of 70 μM. This is better than previously reported work based on the use of ZnO nanostructures. The detection range is 0.1-15 mM which makes the sensor suitable for practical uses in glucose sensing. The sensor was successfully applied to the analysis of human blood serum samples. It is not interfered by common concentrations of ascorbic acid, uric acid, bovine serum albumin, maltose, fructose, and sucrose. Graphical abstract Schematic of the one-step, seedless hydrothermal method utilized for synthesizing vertically aligned ZnO nanotubes on printed circuit board substrates (PCBs). The ZnO nanotubes were used to monitor glucose concentrations in a non-enzymatic fluorescent sensor.

Electrostatic assembly of gold nanoparticles on black phosphorus nanosheets for electrochemical aptasensing of patulin

An aptamer based impedimetric assay for the mycotoxin patulin (PAT) is described. A glassy carbon electrode (GCE) was modified with black phosphorus nanosheets (BP NSs) and modified with PAT aptamer by electrostatic attraction. Detection is based on the variations of electron transfer resistance at the modified electrode surface. This assay can detect PAT over a linear range that extends from 1.0 nM to 1.0 μM with a 0.3 nM detection limit. To improve the performance of the sensor, the BP NS-GCE was further modified with gold nanoparticles and then with thiolated PAT aptamer. This modified electrode, operated at an applied potential of 0.18 V (vs. Ag/AgCl), has a wider linear range (0.1 nM to 10.0 μM) and a lower detection limits (0.03 nM). Both assays were successfully applied to the analysis of (spiked) genuine food samples. Graphical abstract Black phosphorus nanosheets (BP NSs) were used to fabricate an aptamer based assay for patulin. To further improve the performance of the electrode, gold nanoparticles (AuNP) were placed on the surface of black phosphorus nanosheets (AuNP-BP NSs) by electrostatic attraction for patulin aptasensing.

A nanocomposite consisting of gold nanobipyramids and multiwalled carbon nanotubes for amperometric nonenzymatic sensing of glucose and hydrogen peroxide

Gold nanobipyramids were synthesized by a seed-mediated growth method and then supported by multi-walled carbon nanotubes (denoted as AuNBP/MWCNTs). The electrocatalytic activity of the AuNBP/MWCNTs on a glassy carbon electrode (GCE) towards direct glucose oxidation and hydrogen peroxide reduction was superior to that of AuNBPs and MWCNTs. The modified GCE, operated at a typical working voltage of +0.15 V (vs. SCE) and in 0.1 M NaOH solution, exhibits a linear response in the 10 μM to 36.7 mM glucose concentration range with a 3.0 μM detection limit (at S/N = 3) and a sensitivity of 101.2 μA mM^-1 cm^-2. It also demonstrates good sensitivity towards hydrogen peroxide in at pH 7 solution at a working potential of -0.50 V (vs. SCE), with a linear response range from 5.0 μM to 47.3 mM, a sensitivity of 170.6 μA mM^-1 cm^-2 and a detection limit of 1.5 μM. Graphical abstract A electrochemical sensing platform based on the use of gold nanobipyramids and multi-walled carbon nanotubes nanocomposites (AuNBP/MWCNTs) is described for the determination of glucose and hydrogen peroxide.

Chemical Design of Palladium-Based Nanoarchitectures for Catalytic Applications

Palladium (Pd) plays an important role in numerous catalytic reactions, such as methanol and ethanol oxidation, oxygen reduction, hydrogenation, coupling reactions, and carbon monoxide oxidation. Creating Pd-based nanoarchitectures with increased active surface sites, higher density of low-coordinated atoms, and maximized surface coverage for the reactants is important. To address the limitations of pure Pd, various Pd-based nanoarchitectures, including alloys, intermetallics, and supported Pd nanomaterials, have been fabricated by combining Pd with other elements with similar or higher catalytic activity for many catalytic reactions. Herein, recent advances in the preparation of Pd-based nanoarchitectures through solution-phase chemical reduction and electrochemical deposition methods are summarized. Finally, the trend and future outlook in the development of Pd nanocatalysts toward practical catalytic applications are discussed.

Co3O4 Nanopetals on Si as Photoanodes for the Oxidation of Organics

Cobalt oxide nanopetals were grown on silicon electrodes by heat-treating metallic cobalt films deposited by DC magnetron sputtering. We show that cobalt oxide, with this peculiar nanostructure, is active towards the photo-electrochemical oxidation of water as well as of organic molecules, and that its electrochemical properties are directly linked to the structure of its surface. The formation of Co3O4 nanopetals, induced by oxidizing annealing at 300 °C, considerably improves the performance of the material with respect to simple cobalt oxide films. Photocurrent measurements and electrochemical impedance are used to explain the behavior of the different structures and to highlight their potential application in water remediation technologies.

Fluorometric determination of glucose based on a redox reaction between glucose and aminopropyltriethoxysilane and in-situ formation of blue-green emitting silicon nanodots

A method is described for fluorometric detection of glucose. It is based on the finding that silicon nanodots (SNDs) are formed from glucose and aminopropyltriethoxysilane (APTES) under mild experimental conditions. The SNDs thus formed have an average diameter of ∼2 nm, exhibit good water dispersibility, blue fluorescence (with excitation/emission maxima at 410/475 nm), broad pH tolerance, and are photostable. The assay was applied to the quantification of glucose with high sensitivity, good specificity, and over a wide detection range (from 10 μM to 0.9 mM). It was applied to the determination of glucose in spiked serum samples and gave satisfactory results and recoveries. Graphical abstract Schematic presentation of serum glucose detection based on a redox reaction between glucose and aminopropyltriethoxysilane and in-situ formation of blue-green emitting silicon nanodots.