Visual and electrochemical chiral discrimination of tryptophan isomers with shikimic acid chiral ionic liquids-copper ions complex

Efficient discrimination of amino acids (AAs) isomers is of significant importance for life science and analytical chemistry. Here, a dual-mode chiral discrimination strategy is proposed for visual and electrochemical chiral discrimination of tryptophan (Trp) isomers. Shikimic acid chiral ionic liquids (SCIL) is coordinated with copper ions (Cu2+), and the obtained SCIL-Cu2+ can form ternary complexes with the Trp isomers. Owing to the inherent chirality of SCIL and the reverse homochirality of L-Trp and D-Trp, the ternary complex of SCIL-Cu-D-Trp has higher stability than SCIL-Cu-L-Trp, as revealed by the calculated stability constants (K) and changes in Gibbs free energy (ΔG). The difference in the stability can be utilized for the chiral discrimination of L-Trp and D-Trp, resulting in discernible differences in colors and the electrochemical signals of the Trp isomers. Besides Trp, the isomers of phenylalanine (Phe) can also be discriminated by the proposed dual-mode chiral discrimination strategy with the SCIL-Cu2+ complex.

Cu/CuOx@C Composite as a High-Efficiency Electrocatalyst for Oxygen Reduction Reactions

Among clean energy transformation devices, fuel cells have gained special attention over the past years; however, advancing appropriate non-valuable metal impetuses to halfway supplant the customary Pt/C impetus is still in progress. In this paper, we propose a specific electrocatalyst in the formula of highly-active Cu species, associated with coated carbon (Cu@C-800), for oxygen reduction reaction (ORR) through post-treatment of a self-assembled precursor. The optimized catalyst Cu@C-800 showed excellent ORR performance (i.e., the onset potential was 1.00 V vs. RHE, and half-wave potential of 0.81 V vs. RHE), high stability, resistance to methanol, and high four-electron selectivity. The enhancement is attributed to the synergy between the carbon matrix and a high explicit surface region and rich Cu nano-species.

Free-standing hybrid material of Cu/Cu2O/CuO modified by graphene with commercial Cu foil using for non-enzymatic glucose detection

Free-standing Cu/Cu₂O/CuO modified by graphene was formed through two steps: Firstly, the commercial Cu foil was thermal annealed to form Cu/Cu₂O/CuO; Secondly, the Cu/Cu₂O/CuO was modified by graphene through electrochemical exfoliated method. The SEM, XRD, TEM and XPS have been used to characterize the morphology, the crystalline phase, and the surface composition of the hybrid electrode as-prepared. The effects of Cu and its oxides on graphene has been uncovered by the Raman results. The sensitivity of the glucose sensor in 0.1 M NaOH by using the as-prepared hybrid material reaches 3102μA·mM^-1cm^-2within a linear range of 0.002-2.88 mM, which is better than that of the Cu/graphene and the Cu/Cu₂O/CuO prepared at the same conditions. The sensor also shows excellent anti-interference ability, good cycling stability and time stability. The advantage of the sensor is caused by the strengthened synergistic effects between the graphene and the Cu/Cu₂O/CuO due to the alleviated detrimental effects of the metal on the property of the graphene through using oxides middle layer as well as the large active area that obtained. This work provides a new way to study the effects of graphene in improving the property of the metal oxide especially in using for glucose sensor.

Highly Sensitive and Stable Copper-Based SERS Chips Prepared by a Chemical Reduction Method

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction method. In the preparation process, Cu NPs were densely deposited onto fabric supports. The as-prepared Cu-coated fabric was hydrophobic with fairly good SERS performance. The Cu-coated fabric was able to be used as a SERS chip to detect crystal violet, and it exhibited an enhancement factor of 2.0 × 106 and gave a limit of detection (LOD) as low as 10-8 M. The hydrophobicity of the Cu membrane on the fabric is favorable to cleaning background interference signals and promoting the stability of Cu NPs to environment oxidation. However, this Cu SERS chip was still poor in its long-term stability. The SERS intensity on the chip was decreased to 18% of the original one after it was stored in air for 60 days. A simple introduction of Ag onto the clean Cu surface was achieved by a replacement reaction to further enhance the SERS performances of the Cu chips. The Ag-modified Cu chips showed an increase of the enhancement factor to 7.6 × 106 due to the plasmonic coupling between Cu and Ag in nanoscale, and decreased the LOD of CV to 10-11 M by three orders of magnitude. Owing to the additional protection of Ag shell, the SERS intensity of the Cu-Ag chip after a two-month storing maintained 80% of the original intensity. The Cu-Ag SERS chips were also applied to detect other organics, and showing wide linearity range and low LOD values for the quantitative detection.

Stable, Efficient, Copper Coordination Polymer-Derived Heterostructured Catalyst for Oxygen Evolution under pH-Universal Conditions

The constructure of a heterostructured interface is an effective way to design highly durable and efficient water oxidation electrocatalysts. Herein, Cu/CuCN with heterointerfaces is the first synthesized case through a simple epitaxial-like growth method, displaying superior activity and stability under pH-universal media. Associated with high electron transport and transfer of the epitaxial interfacial area, the Cu/CuCN pre-catalyst is applied to deliver the oxygen evolution reaction (OER) with lower overpotentials of 250 mV (forward scan) and 380 mV (backward scan) at 10 mA cm^-2 and demonstrates better intrinsic activity (j_ECSA of 1.0 mA cm^-2 at 420 mV) and impressive stability (136 h) in 1.0 M KOH, which exceeds most previous catalysts. Even using a nominal voltage of 1.5 V of a AA battery can drive the overall water-splitting setup. Experiments combined with theoretical simulations further uncover the existence of CuO species at the heterointerface during basic OER, which is evidence of better OER performance with abundant active sites that accelerate the conversion kinetics.

Hollow Nanotube Ru/Cu2+1 O Supported on Copper Foam as a Bifunctional Catalyst for Overall Water Splitting

Hydrogen energy is considered as one of the ideal clean energies for solving the energy shortage and environmental issues, and developing highly efficient electrocatalysts for overall water splitting to produce hydrogen is still a huge challenge. Herein, for the first time, Ru-doped Cu₂₊₁ O vertically arranged nanotube arrays in situ grown on Cu foam (Ru/Cu₂₊₁ O NT/CuF) are reported and further investigated for their catalytic properties for overall water splitting. The Ru/Cu₂₊₁ O NT/CuF presents ultrahigh catalytic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline conditions, and it exhibits a small overpotential of 32 mV at 10 mA cm^-2 in the HER, and only needs 210 mV overpotential to achieve a current density of 10 mA cm^-2 in the OER. Importantly, the alkaline electrolyzer using Ru/Cu₂₊₁ O NT/CuF as a bifunctional electrocatalyst only needs 1.53 V voltage to deliver a current density of 10 mA cm^-2 , which is much lower than the benchmark of IrO₂ (+)/Pt(-) counterpart (1.64 V at 10 mA cm^-2 ). The excellent performance of the Ru/Cu₂₊₁ O NT/CuF catalyst is attributed to its high conductive substrate and special Ru-doped nanotube structure, which provides a high electrochemical active surface area and 3D gas diffusion channel.