Microplasma and quenching-induced Co doped NiMoO(4) nanorods with oxygen vacancies for electrochemical determination of glucose in food and serum

Electrochemical pH modulator coupled with Ni-based electrode for glucose sensing

The non-enzymatic electrochemical detection of glucose by direct oxidation using electrodes modified with suitable electrocatalysts is now well-established. However, it most often requires highly alkaline media, limiting dramatically the use of such electrodes at neutral pH. This is notably the case of Ni-based electrodes. Here, we propose a new concept to overcome this limitation. It implies the use of an additional stainless-steel grid electrode positioned parallel and close (0.6 mm) to the working Ni-based electrode. In such configuration, applying a suitable cathodic potential (-1.2 V) to the grid enables the solvent reduction, generating OH- species that contribute to increasing the pH in the vicinity of the Ni-based electrode, thereby enabling effective electrochemical detection of glucose without the need for any alkaline additives in the medium. The present manuscript presents a proof-of-concept for the proposed approach based on a 3D-printed prototype. Under optimized conditions for both preparation of the nickel electrode (electrodeposition from 0.4 M NiCl2 for 120 s at a current density of -354 mA cm-2) and for the operation of the electrochemical pH modulator (at -1.2 V for 400 s), the amperometric detection of glucose at an applied potential of +0.55 V exhibited linearly over the concentration range from 0.1 to 1 mM, with a limit of detection estimated to 73 μM. The method offers promising perspectives for enzyme-less, non-invasive electrochemical detection of glucose in real media.

Confinement synthesis of few-layer MXene-cobalt@N-doped carbon and its application for electrochemical sensing

Herein, the few-layer Ti3C2Tx nanosheets loaded zeolitic imidazolate framework-67 nanoplates (Ti3C2Tx-ZIF-67) with a unique structure has been synthesized by surfactant control method, and then is employed as the core of precursor. A thin layer of polydopamine as the shell of precursor covered Ti3C2Tx-ZIF-67 forms a micro-nano reactor, leading to the confinement carbonization process. Consequently, a novel sensing material that few-layer Ti3C2Tx nanosheets loaded Co nanoparticles coated N-doped carbon (Ti3C2Tx-Co@NC) is obtained for the non-enzymatic determination of glucose. Owing to the impressive structure, the established glucose sensor based on Ti3C2Tx-Co@NC/glassy carbon electrode exhibits 0.5-100.0 μM of linear detection range and 66.8 nM of detection limit, which tends to detect low concentration of glucose. The synergistic few-layer Ti3C2Tx nanosheets, Co nanoparticles and NC are considered through a series of control experiments. First, few-layer Ti3C2Tx nanosheets provide a good transport channel for electron transfer, resulting in the lower steric hindrance. Second, Co nanoparticles provide active centers for the electrochemical detection. Third, N-doped carbon with conductivity and hydrophilia plays the role of stabilizing material structure to prevent the fragmentation of Ti3C2Tx and the agglomeration of Co nanoparticles. Such work proposes a confined strategy to develop MXene-ZIF-67-derived nanocomposite with high-performance structure.

Microplasma-assisted construction of cross-linked network hierarchical structure of NiMoO4 nanorods @NiCo-LDH nanosheets for electrochemical sensing of non-enzymatic H2O2 in food

The accumulation of small doses of hydrogen peroxide (H2O2) into food can cause many diseases in the human body, and it is urgent to develop efficient detection methods of H2O2. Herein, the hierarchical structure composite of NiCo-LDH nanosheets crosslinked NiMoO4 nanorods was grown in situ on carbon cloth (NiMoO4 NRs@NiCo-LDH NSs/CC) by micro-plasma assisted hydrothermal method. Thanks to the synergistic effect of three metals and (NiMoO4 NRs@NiCo-LDH NSs/CC) provided by nanorods/nanosheets hierarchical structure, NiMoO4 NRs@NiCo-LDH NSs/CC exposes more active sites and achieves rapid electron transfer. The H2O2 electrochemical sensor was constructed as the working electrode with a linear range of 1 μmol L-1 to 9.0 mmol L-1 and detection limit of 112 nmol L-1. In addition, the sensor has been successfully applied to the detection of H2O2 in food samples, the recovery rate is 95.2%-106.62%, RSD < 4.89%.

Microplasma-induced in situ rapid synthesis of CoSe nanosphere@N-doped polymeric carbon dots derived from ZIF-67 for highly sensitive dopamine detection

BACKGROUND

Designing a fast and sensitive electrochemical sensing platform to achieve selective quantitative detection of dopamine (DA) is a great challenge. Combining transition metal selenides (TMSs) with a variety of conductive carbonaceous materials is one of the effective strategies to improve the electrocatalytic activity of TMSs. However, most of the reported preparation methods of TMSs/carbon-based composite nanomaterials need to be annealed at a high temperature for a long time, which does not meet the requirements of sustainable development. Therefore, it is of great significance to explore an energy-efficient and fast method to prepare these compounds.

RESULTS

In this work, CoSe nanosphere@nitrogen-doped polymeric carbon dots are rapid prepared using ZIF precursor by simple dielectric barrier discharge (DBD) microplasma-induced on carbon cloth (CoSe NSs@N-PCDs/CC) for the first time. Owing to the fact that CoSe can promote rapid proton transfer, N-CDs has a high specific surface area, rich functional groups and electrical conductivity, this electrode exhibits highly sensitive non-enzymatic electrochemical sensing performance for DA detection. The linear range and detection limit are 0.1 μM-50 μM and 40.2 nM, respectively, and it have been successfully applied to the determination of DA levels in real human serum samples. Theoretical DFT calculations show that the most efficient interaction with DA on the surface of CoSe (101) can promote electrochemical reactions and catalyze DA oxidation.

SIGNIFICANCE

Using ZIF as precursor, CoSe NSs@N-PCDs/CC electrochemical electrode was synthesized in situ by simple and energy-saving DBD microplasma. CoSe NSs can effectively prevent the aggregation of function-rich N-PCDs and significantly improve the electrocatalytic activity of the composite. The mechanism of high selectivity of CoSe NSs@N-PCDs/CC electrode to DA was studied by DFT calculation. This work provides a new idea for the fast and green synthesis of transition metal and carbon-based nanomaterials by microplasma.

Incorporation of laser-induced graphene with hierarchical NiCo layered double hydroxide nanosheets for electrochemical determination of glucose in food and serum

Dependable and sensitive glucose (Glu) testing in foodstuff and blood serum is highly desirable to prevent and treat diabetes. Electrochemical quantification of Glu has attracted great interests due to the advantages, including simple operation, higher sensitivity, easy miniaturization, ease of on-site and wearable detection as well as fast response. High costs and environmental dependence of enzymes pose a challenge to the electrochemical enzymatic biosensors. Nonenzymatic electrochemical Glu sensors are urgently needed to aid the Glu detection in human serum and food samples. To fabricate flexible Glu electrochemical sensors, designing suitable electrode substrate and efficient electrocatalyst is of paramount significance. Herein, the porous patterned laser-induced graphene (LIG) was fabricated on polyimide substrates through an efficient laser-inducing technology, and then used directly as the electrode substrate. Electrochemical deposition of NiCo layered double hydroxide (LDH) nanoflakes on the LIG surface was then conducted to achieve NiCo-LDH/LIG electrode as a Glu sensor. Under optimal conditions, this sensor displays a low detection limit of 0.05 μM. Two sets of broad detection linear ranges were found to be from 0.5 to 270 μM and from 0.27 to 3.6 mM, with high sensitivities of 9.750 μA μM-1 cm-2 and 3.760 μA μM-1 cm-2, respectively. The enhanced performance was ascribed to the cooperative action of NiCo-LDH and LIG, in which porous LIG provides extraordinary electroconductibility and a high surface area, while NiCo-LDH offers numerous exposed active sites and outstanding electrocatalytic performance. Practical application was further verified during the Glu detection in human serum and food samples. This research confirms that the NiCo-LDH/LIG composite is a prospective electrode for high-performance Glu sensor and provides a way of developing nonenzymatic electrochemical sensors to analyze the Glu in human serum and food samples, opening new avenues in electrochemical sensing.

A novel hollow CuMn-PBA@NiCo-LDH nanobox for efficient detection of glucose in food

Designing a rapid and sensitive glucose detection method is of great significance to public health. Herein, hollow CuMn-PBA@NiCo-LDH nanoboxes (CuMn-PBA@NiCo-LDH NBs) were prepared using acid etching, cation exchange, and reflux method. The modified electrode exhibited outstanding electrocatalytic performance for glucose oxidation due to the unique hollow nanostructure and synergistic effects. The CuMn-PBA@NiCo-LDH NBs electrode displayed excellent electrocatalytic oxidation activity for glucose in an alkaline solution. Under optimal conditions, the electrode achieved a wide linear range (0.0005-1 mmol L-1, and 1-7 mmol L-1) and high sensitivity (10,300 μA L/mmol cm-2 and 5310 μA L/mmol cm-2), with a limit of detection (LOD) of 19 nmol L-1. The feasibility of the sensor applied to the detection of glucose was verified in real food samples through spiked recovery experiments. This electrode material offers an alternative method for the non-enzymatic glucose sensors.

NiCo-LDH coupled with 2D ZIF-derived Co nitrogen doped carbon nanosheet arrays as a self-supporting electrocatalyst for detection of formaldehyde

Formaldehyde is susceptible to illegal addition to foodstuffs to extend their shelf life due to its antimicrobial, preservative and bleaching properties. In this study, a self-supporting "nanosheet on nanosheet" arrays electrocatalyst with core-shell heterostructure was prepared in situ by coupling NiCo layer double hydroxide with 2D ZIF derived Co-nitrogen-doped porous carbon on carbon cloth (Co-N/C@NiCo-LDH NSAs/CC). Co-N/C nanosheet arrays act as a scaffold core with good electrical conductivity, providing more NiCo-LDH nucleation sites to avoid NiCo-LDH agglomeration, thus having fast mass/charge transfer performance. While the NiCo-LDH nanosheet arrays shell with high specific surface area provide more active sites for electrochemical reactions. As an electrocatalytic sensing electrode, Co-N/C@NiCo-LDH NSAs/CC has a wide linear range of 1 μM to 13 mM for formaldehyde detection, and the detection limit is 82 nM. Besides, the sensor has been applied to the detection of formaldehyde in food samples with satisfactory results.

Highly sensitive detection of glucose at a novel non-enzyme electrochemical sensing based on Mo-doped CoO Nanosheets

In this work, a Mo doped CoO nanosheet grown on nickel foam (labeled as: Mo-CoO) with defect-rich and improved electron transfer capacity was designed to be used as a novel non-enzyme electrode material. Physical characterizations demonstrated the Mo elements were doped inside of the samples and they were mutually stabilized with each other, resulting in a high structural stability electrochemical catalytical activity even if the content of Mo was low. For non-enzymatic glucose electrochemical sensing, the prepared Mo-CoO-1 showed a remarkable sensitivity of 89.3 mA cm-2  mM-1 , and a low detection limit of 0.43 μM. Density functional theory (DFT) studies revealed that the doped Mo atom exhibited a higher d-band center compared to the Co atom. A stronger p-d orbital hybridization between the glucose and the Mo atoms indicated the enhancement of glucose adsorption and activation. Importantly, Mo-CoO-1 provided a good selectivity and long-term stability, which can be expected to be used in future practical applications.

Layered bimetallic hydroxide nanocage assembled on MnO2 nanotubes: A hierarchical porous sugar gourd-like electrocatalyst for the sensitive detection of hydrogen peroxide in food

Hydrogen peroxide is used widely as a disinfection or bleaching additive during processing in the food industry. However, excessive residues of hydrogen peroxide in food have serious human health implications. In the present study, a novel electrochemical sensing electrode (MnO₂/ZIF-67@LDH) with hierarchical porous sugar gourd-like structure was fabricated through a multi-step hydrothermal method using ZIF as the precursor. The unique porous nanocage structure of the sensing electrode provided multidimensional charge transfer channels and accelerated the electron transfer rate. As a hydrogen peroxide sensor, the electrode had two detection linear ranges of 1×10^-3-4 mmol L^-1 and 4-8 mmol L^-1, and the detection limit was 0.26 µmol L^-1. The MnO₂/ZIF-67@LDH sensor was also applied to determine the content of hydrogen peroxide in actual food samples of juice and milk, and satisfactory recovery were achieved. The present study provides a novel and effective design strategy for the construction of electrochemical sensing electrodes.