A Flexible Portable Glucose Sensor Based on Hierarchical Arrays of Au@Cu(OH)2 Nanograss

Discovery of Dual Ion-Electron Conductivity of Metal-Organic Frameworks via Machine Learning-Guided Experimentation

Identifying conductive metal-organic frameworks (MOFs) with a coupled ion-electron behavior from a vast array of existing MOFs offers a cost-effective strategy to tap into their potential in energy storage applications. This study employs classification and regression machine learning (ML) to rapidly screen the CoREMOF database and experimental methodologies to validate ML predictions. This process revealed the structure-property relationships contributing to MOFs' bulk ion-electron conductivity. Among the 60 conductive compounds predicted, only two p-type conductive MOFs, [Cu3(μ3-OH) (μ3-C4H2N2O2)3(H3O)]·2C2H5OH·4H2O (1) and NH4[Cu3(μ3-OH)(μ3-C4H2N2O2)3]·8H2O or (2) (C4H2N2O = 1H-pyrazole-4-carboxylic acid), were validated for their coupled electron-ion behavior. MOFs utilize earth-abundant copper and pyrazoles as ligands, demonstrating significant potential following thorough electrochemical characterization. Further analysis confirmed the critical role of strong σ-donating, π-accepting, and redox-active ligands in promoting electron mobility. In-depth structural investigations revealed that the presence of the O-Cu-N chain significantly influences conductivity, outperforming MOFs with only Cu-N or Cu-O bonds. Additionally, this study highlights how higher ionic conductivity is correlated with the ion mobility through linkers in 1 or the presence of ammonium ions in 2. These structure-property relationships offer valuable insights for future research in using ML coupled with experimentation to design MOFs containing earth-abundant reagents for ion-electron conductivity without employing a host-guest MOF strategy.

Wearable Noninvasive Glucose Sensor Based on CuxO NFs/Cu NPs Nanocomposites

Designing highly active material to fabricate a high-performance noninvasive wearable glucose sensor was of great importance for diabetes monitoring. In this work, we developed CuxO nanoflakes (NFs)/Cu nanoparticles (NPs) nanocomposites to serve as the sensing materials for noninvasive sweat-based wearable glucose sensors. We involve CuCl2 to enhance the oxidation of Cu NPs to generate Cu2O/CuO NFs on the surface. Due to more active sites endowed by the CuxO NFs, the as-prepared sample exhibited high sensitivity (779 μA mM-1 cm-2) for noninvasive wearable sweat sensing. Combined with a low detection limit (79.1 nM), high selectivity and the durability of bending and twisting, the CuxO NFs/Cu NPs-based sensor can detect the glucose level change of sweat in daily life. Such a high-performance wearable sensor fabricated by a convenient method provides a facile way to design copper oxide nanomaterials for noninvasive wearable glucose sensors.

Hierarchical Structures Composed of Cu(OH)2 Nanograss within Directional Microporous Cu for Glucose Sensing

Cu(OH)₂ nanomaterials are widely investigated for non-enzymatic glucose sensors due to their low-cost and excellent performance. Cu(OH)₂ nanomaterials usually grow on substrates to form sensor electrodes. Reported works mainly focus on structure adjusting of the Cu(OH)₂ nanostructures, while the optimization of substrates is still lacking. In the present work, directional porous Cu (DPC) was applied as the substrate for the growth of Cu(OH)₂ nanograss (NG), and hierarchical structures of Cu(OH)₂@DPC were prepared by alkaline oxidation. The morphology and microstructure evolution of the prepared hierarchical structures was investigated, and the non-enzymatic glucose sensing performance was evaluated. Cu(OH)₂@DPC exhibits enhanced comprehensive non-enzymatic glucose sensing performance compared to the reported ones, which may benefit from both the effective adsorption of the Cu(OH)₂ NG with a relatively high surface area and the high solute exchange of the DPC by a channel effect. This work provides new insights into the further improvement of the non-enzymatic glucose sensing performance of Cu(OH)₂ nanostructures by optimizing the substrate structure.

Voltammetric determination of pethidine in biofluids at a carbon cloth electrode modified by carbon selenide nanofilm

Developing a sensitive portable sensor for the screening of illicit drugs is always challenging. Due to the importance of pethidine (PTD) tracking in addiction diagnosis, many demands have recently increased for a selective and real-time sensor. Herein, a simple electrochemical sensor has been developed based on conductive carbon cloth (CC) modified with carbon selenide nanofilms (CSe₂NF) to provide a CSe₂NF/CC electrode as a novel PTD sensing tool. Profiting from the ingenious design of doping strategy during the synthesis process, Se was doped in the carbonaceous skeleton of the CC. Thus, the active surface area of the CSe₂NF (4.61 cm²) increased respect to the unmodified CC (0.094 cm²) to embed a suitable sensing interface in the fast PTD assay. By optimizing some effective experimental parameters such as pH, supporting electrolyte, Se powder amount, scan rate and accumulation time, the sensor catalyzed efficiently the oxidation reaction of PTD at 0.97 V. Based on peak current variations, the PTD was measured over a broad concentration range from 29 nM up to 181.8 μM with a limit of detection (LOD) as low as 19.3 nM compared to the other reported PTD sensors. The developed flexible sensor recognized the spiked PTD concentrations in some biofluids, including human blood, urine and saliva. The results of PTD analysis in the non-spiked and spiked blood, urine and saliva samples as the real samples by the developed sensor were validated by HPLC analysis as the reference method using t-test statistical method at confidence level of 5%. This sensing strategy based on the binder-free electrode could be promising for designing some sizable wearable sensors at a low cost. The high sensitivity of the sensor, which is a bonus for the rapid and on-site measurement of PTD, may open up a route for noninvasive routine analysis in clinical samples.

NiCo-LDH nanoflake arrays-supported Au nanoparticles on copper foam as a highly sensitive electrochemical non-enzymatic glucose sensor

The detection of glucose in human blood is of great importance in the diagnosis and prevention of diabetes. In this work, we fabricated a novel electrochemical non-enzymatic glucose sensor, NiCo-LDH nanoflake arrays-supported Au nanoparticles on copper foam (NiCo-LDH@ Au/Cu) by galvanic replacement and electrodeposition methods. Owing to the synergistic effect of three-dimensional (3D) architecture of Cu foam, high electrocatalytic activity of Au nanoparticles and NiCo-LDH nanoflake arrays, the NiCo-LDH@Au/Cu electrode exhibits excellent electrocatalytic ability for glucose oxidation in NaOH solution. Under optimized conditions, the NiCo-LDH@Au/Cu electrode shows excellent activity with a linear range from 0.5 to 3000 μM at the potential of 0.50 V (vs. Ag/AgCl), a low detection limit of 0.23 μM (S/N = 3), an ultra-prompt response time of 0.5 s, and a high sensitivity of 23100 μA mM^-1 cm^-2, as well as good selectivity and stability. Furthermore, the as-fabricated non-enzymatic glucose sensor was successfully applied to the glucose detection in human serum as a promising candidate in the development of electrochemical non-enzymatic glucose sensor.

A three-electrode integrated electrochemical platform based on nanoporous gold for the simultaneous determination of hydroquinone and catechol with high selectivity

A novel integrated electrochemical platform was built for the simultaneous determination of hydroquinone and catechol.