Construction of a binder-free non-enzymatic glucose sensor based on Cu@Ni core-shell nanoparticles anchored on 3D chiral carbon nanocoils-nickel foam hierarchical scaffold.

Bimetallic nanostructures composited with carbonaceous materials are the potential contenders for quantitative glucose measurement owing to their unique nanostructures, high biomimetic activity, synergistic effects, good conductivity and chemical stability. In the present work, chemical vapors deposition technique has been employed to grow 3D carbon nanocoils (CNCs) with a chiral morphology on hierarchical macroporous nickel foam (NF) to get a CNCs/NF scaffold. Following, bimetallic Cu@Ni core-shell nanoparticles (CSNPs) are effectively coupled with this scaffold through a facile solvothermal route in order to fabricate a binder-free novel Cu@Ni CSNPs/CNCs/NF hybrid nanostructure. The constructed free-standing 3D hierarchical composite electrode guarantees highly efficient glucose redox activity due to core-shell synergistic effects, enhanced electrochemical active surface area, excellent electrochemical stability, improved conductivity with better ion diffusivity and accelerated reaction kinetics. Being a non-enzymatic glucose sensor, this electrode achieves highly swift response time of 0.1 s, ultra-high sensitivity of 6905 µA mM-1 cm-2, low limit of detection of 0.03 µM along with potential selectivity and good storage stability. Moreover, the proposed sensor is also tested successfully for the determination of glucose concentration in human serum samples under good recovery ranging from 96.6 to 102.1 %. The 3D Cu@Ni CSNPs/CNCs/NF composite electrode with unprecedented catalytic performance can be utilized as an ideal biomimetic catalyst in the field of non-enzymatic glucose sensing.

Solvothermal synthesis of 3D hierarchical Cu2FeSnS4 microspheres for photocatalytic degradation of organic pollutants.

In this work, we prepared Cu2FeSnS4 (CFTS) microspheres via solvothermal method and studied their photocatalytic performance towards the degradation of organic pollutants. With increasing solvothermal temperature from 160 °C to 180 °C, the morphology of CFTS changes from irregular 2D to hierarchical 3D shapes. Hierarchical 3D CFTS microspheres packed with 2D nanosheets were successfully prepared at 180 °C. During the solvothermal process, octadecyl amine (ODA) acts as a capping agent to prevent the aggregation of particles, while L-cystine functions as an environmentally friendly sulfur source and complexing reagent. The large surface area and mesoporous structure of the as-prepared 3D hierarchical CFTS microspheres provide more active sites, enhance visible light absorption and promote charge separation and transfer, leading to the improved photodegradation performance for RhB and MB compared to the samples prepared at the temperature lower than 180 °C. This work provides a simple and low-cost method for the synthesis of 3D hierarchical CFTS towards photocatalytic applications.

Highly Sensitive, Ultrafast, and Broadband Photo-Detecting Field-Effect Transistor with Transition-Metal Dichalcogenide van der Waals Heterostructures of MoTe2 and PdSe2.

Recently, van der Waals heterostructures (vdWHs) based on transition-metal dichalcogenides (TMDs) have attracted significant attention owing to their superior capabilities and multiple functionalities. Herein, a novel vdWH field-effect transistor (FET) composed of molybdenum ditelluride (MoTe2 ) and palladium diselenide (PdSe2 ) is studied for highly sensitive photodetection performance in the broad visible and near-infrared (VNIR) region. A high rectification ratio of 6.3 × 105 is obtained, stemming from the sharp interface and low Schottky barriers of the MoTe2 /PdSe2 vdWHs. It is also successfully demonstrated that the vdWH FET exhibits highly sensitive photo-detecting abilities, such as noticeably high photoresponsivity (1.24 × 105 A W-1 ), specific detectivity (2.42 × 1014 Jones), and good external quantum efficiency (3.5 × 106 ), not only due to the intra-TMD band-to-band transition but also due to the inter-TMD charge transfer (CT) transition. Further, rapid rise (16.1 µs) and decay (31.1 µs) times are obtained under incident light with a wavelength of 2000 nm due to the CT transition, representing an outcome one order of magnitude faster than values currently in the literature. Such TMD-based vdWH FETs would improve the photo-gating characteristics and provide a platform for the realization of a highly sensitive photodetector in the broad VNIR region.

Electron number density conservation model combined with a self-absorption correction methodology for analysis of nanostructure plasma using laser-induced breakdown spectroscopy.

We studied laser ablation and plasma property evolution for a nickel (Ni) doped tin (Sn) oxide nanostructures target using laser-induced breakdown spectroscopy (LIBS). The transition metal Ni doped tin oxide nanostructures were synthesized by co-precipitation and hydrothermal methodologies. The size of prepared nanoparticles was verified by X-ray diffraction and transmission electron microscopy techniques. A frequency-doubled pulsed Nd:YAG laser with a wavelength of 532 nm was used to produce ablated plasma nanostructures. Ablation of doped and undoped nanostructures revealed salient-enhanced spectral emissions compared with their bulky counterparts. The emission lines of the constituent elements of doped material were used to find plasma parameters. The plasma temperature was estimated from a Boltzmann plot, and the electron number density was determined from the Saha-Boltzmann equation. The self-absorption effect has been observed in tiny plasma of nanostructures. The affected profiles of spectral lines of Ni and Sn nanoparticles due to self-absorption in LIBS spectra were corrected by the internal reference self-absorption correction (IRSAC) methodology. After correction of emitted line intensities by IRSAC, the electron number density (END) conservation approach was applied for quantitative analysis of doped nanostructures. In the END conservation approach, quantitative analysis of samples was carried out using electron number densities. Quantitative results derived from the END conservation approach at high and low concentrations exhibited good correlation when these were compared and validated with results from a conventional calibration free approach and the standard recognized energy dispersive X-ray technique.

An effective hydroxylation route for a highly sensitive glucose sensor using APTES/GOx functionalized AlGaN/GaN high electron mobility transistor.

A highly sensitive glucose sensor based on AlGaN/GaN high electron mobility transistor (HEMT) has been fabricated. The hydroxyl groups on the GaN surface were achieved by the decomposition of hydrogen peroxide solution (H2O2) under UV irradiation for the production of hydroxyl radicals. The self-assembled monolayers (SAMs) of 3-aminopropyltriethoxysilane (APTES) with terminal amino groups formed on the hydroxylation surface were used as substrates for glucose oxidase (GOx) immobilization. The chemical groups on the GaN surface after hydroxylation were confirmed by X-ray photoelectron spectroscopy. From the analysis of current signals, the biosensor constructed with APTES/GOx exhibited good current response to glucose over a linear range from 10 to 100 µM with a sensitivity of 3.15 × 104 µA mM-1 cm-2 and a detection limit of 10 nM. Meanwhile, the anticipated idea about the hydroxylation of GaN surface, can be an efficient approach for the design of AlGaN/GaN HEMT based biosensors in the future.