Green Synthesis of Carbon Quantum dots Derived from Lycium barbarum for Effective Fluorescence Detection of Cr (VI) Sensing.

Green and economical self-doped nitrogen-containing fluorescent carbon quantum dots (N-CQDs) were synthesized using a one-pot hydrothermal treatment method. The optical and structural properties of the N-CQDs were investigated in detail by UV-vis and fluorescence spectroscopy, X-ray diffraction (XRD) techniques, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) spectroscopy, and elemental analysis illustrate the surface function and composition of N-CQDs. N-CQDs emit a broad fluorescence between365 Ì´ 465 nm and fluoresce most strongly at the excitation wavelength of 415 nm. Meanwhile, Cr (VI) could significantly burst the fluorescence intensity of N-CQDs. N-CQDs showed an excellent sensitivity and selectivity to Cr (VI), which exhibited good linearity in the range of 0 Ì´ 40 µmol/L with a detection limit of 0.16 µmol/L. In addition, the mechanism of Fluorescence quenching of N-CQDs by Cr (VI) was investigated. This work well provides a research idea for the preparation of green carbon quantum dots from biomass and their use for the detection of metal ions.

Synergistic Incorporating RuO2 and NiFeOOH Layers onto Ni3 S2 Nanoflakes with Modulated Electron Structure for Efficient Water Splitting.

Synergistic electronic modulations is an effective strategy to develop efficient and stable electrocatalysts for the electrochemical hydrogen production via water splitting. Herein, tremella-like Ni3 S2 @RuO2 and Ni3 S2 @NiFeOOH heterostructures catalysts are constructed on Ni foams (NF) by coupling RuO2 and NiFeOOH on Ni3 S2 nanoflake arrays. The resulting Ni3 S2 @RuO2 /NF electrode exhibits top-level hydrogen evolution reaction electrocatalysis with an extremely low overpotential of 12 mV at 10 mA cm-2 and a Tafel slope of 30.7 mV dec-1 , as well as the as-obtained Ni3 S2 @NiFeOOH/NF electrode with tunable binding energy for OH* intermediates shows remarkable oxygen evolution reaction electrocatalysis with an overpotential of 227 mV at 10 mA cm-2 . The electrolyzer employing Ni3 S2 @RuO2 /NF electrode for cathodic H2 production and Ni3 S2 @NiFeOOH/NF for anodic O2 production merely needs a low voltage of 1.47 V to drive 10 mA cm-2 with excellent durability. The combined theoretical calculation and X-ray photoelectron spectroscopy investigation reveal that heterogeneous configuration can induce electron transfer from Ni3 S2 to RuO2 through NiRu/SRu bonds, and thus tailor the d-band center and optimize the activated H2 O/H* Gibbs free energies for enhanced hydrogen evolution reaction on Ni3 S2 @RuO2 . This study may shed new light on the construction of heterostructures as highest-performing electrocatalysts and offer unique insight into the theory mechanism.

Wool-Based Carbon Fiber/MoS2 Composite Prepared by Low-Temperature Catalytic Hydrothermal Method and Its Application in the Field of Gas Sensors.

Under the background of the Paris Agreement on reducing greenhouse gases, waste wools were converted into wool carbon fiber (WCF) and WCF-MoS2 composites by low-temperature catalytic hydrothermal carbonization. Their structures and gas-sensing performances were studied for the first time. Due to the existence of heterojunctions, the responses of the WCF-MoS2 composite to the five analytes were 3-400 times those of MoS2 and 2-11 times those of WCF. Interestingly, because of the N, P, and S elements contained in wools, the WCF prepared by the hydrothermal method was realized the doping of N, P, and S, which caused the sensing curves of WCF to have different shapes for different analytes. This characteristic was also well demonstrated by the WCF-MoS2 composite, which inspired us to realize the discriminative detection only by a single WCF-MoS2 sensor and image recognition technology. What's more, the WCF-MoS2 composite also showed a high sensitivity, a high selectivity, and a rapid response to NH3. The response time and the recovery time to 3 ppm NH3 were about 16 and 5 s, respectively. The detection of limit of WCF-MoS2 for NH3 was 19.1 ppb. This work provides a new idea for the development of sensors and the resource utilization of wool waste.

Enhanced Raman scattering in porous silicon grating.

The enhancement of Raman signal on monocrystalline silicon gratings with varying groove depths and on porous silicon grating were studied for a highly sensitive surface enhanced Raman scattering (SERS) response. In the experiment conducted, porous silicon gratings were fabricated. Silver nanoparticles (Ag NPs) were then deposited on the porous silicon grating to enhance the Raman signal of the detective objects. Results show that the enhancement of Raman signal on silicon grating improved when groove depth increased. The enhanced performance of Raman signal on porous silicon grating was also further improved. The Rhodamine SERS response based on Ag NPs/ porous silicon grating substrates was enhanced relative to the SERS response on Ag NPs/ porous silicon substrates. Ag NPs / porous silicon grating SERS substrate system achieved a highly sensitive SERS response due to the coupling of various Raman enhancement factors.

High Sensitivity Detection of CdSe/ZnS Quantum Dot-Labeled DNA Based on N-type Porous Silicon Microcavities.

N-type macroporous silicon microcavity structures were prepared using electrochemical etching in an HF solution in the absence of light and oxidants. The CdSe/ZnS water-soluble quantum dot-labeled DNA target molecules were detected by monitoring the microcavity reflectance spectrum, which was characterized by the reflectance spectrum defect state position shift resulting from changes to the structures' refractive index. Quantum dots with a high refractive index and DNA coupling can improve the detection sensitivity by amplifying the optical response signals of the target DNA. The experimental results show that DNA combined with a quantum dot can improve the sensitivity of DNA detection by more than five times.

Hybridization assay of insect antifreezing protein gene by novel multilayered porous silicon nucleic acid biosensor.

A fabrication of a novel simple porous silicon polybasic photonic crystal with symmetrical structure has been reported as a nucleic acid biosensor for detecting antifreeze protein gene in insects (Microdera puntipennis dzhungarica), which would be helpful in the development of some new transgenic plants with tolerance of freezing stress. Compared to various porous silicon-based photonic configurations, porous silicon polytype layered structure is quite easy to prepare and shows more stability; moreover, polybasic photonic crystals with symmetrical structure exhibit interesting optical properties with a sharp resonance in the reflectance spectrum, giving a higher Q factor which causes higher sensitivity for sensing performance. In this experiment, DNA oligonucleotides were immobilized into the porous silicon pores using a standard crosslink chemistry method. The porous silicon polybasic symmetrical structure sensor possesses high specificity in performing controlled experiments with non-complementary DNA. The detection limit was found to be 21.3nM for DNA oligonucleotides. The fabricated multilayered porous silicon-based DNA biosensor has potential commercial applications in clinical chemistry for determination of an antifreeze protein gene or other genes.