Porous Graphene Oxide Films Prepared via the Breath-Figure Method: A Simple Strategy for Switching Access of Redox Species to an Electrode Surface

Surface-Roughened Graphene Oxide Microfibers Enhance Electrochemical Reversibility

Here, we provide an optimized method for fabricating surface-roughened graphene oxide disk microelectrodes (GFMEs) with enhanced defect density to generate a more suitable electrode surface for dopamine detection with fast-scan cyclic voltammetry (FSCV). FSCV detection, which is often influenced by adsorption-based surface interactions, is commonly impacted by the chemical and geometric structure of the electrode's surface, and graphene oxide is a tunable carbon-based nanomaterial capable of enhancing these two key characteristics. Synthesized GFMEs possess exquisite electronic and mechanical properties. We have optimized an applied inert argon (Ar) plasma treatment to increase defect density, with minimal changes in chemical functionality, for enhanced surface crevices to momentarily trap dopamine during detection. Optimal Ar plasma treatment (100 sccm, 60 s, 100 W) generates crevice depths of 33.4 ± 2.3 nm with high edge plane character enhancing dopamine interfacial interactions. Increases in GFME surface roughness improve electron transfer rates and limit diffusional rates out of the crevices to create nearly reversible dopamine electrochemical redox interactions. The utility of surface-roughened disk GFMEs provides comparable detection sensitivities to traditional cylindrical carbon fiber microelectrodes while improving temporal resolution ten-fold with amplified oxidation current due to dopamine cyclization. Overall, surface-roughened GFMEs enable improved adsorption interactions, momentary trapping, and current amplification, expanding the utility of GO microelectrodes for FSCV detection.

Applications of Graphene in Five Senses, Nervous System, and Artificial Muscles

Graphene remains of great interest in biomedical applications because of biocompatibility. Diseases relating to human senses interfere with life satisfaction and happiness. Therefore, the restoration by artificial organs or sensory devices may bring a bright future by the recovery of senses in patients. In this review, we update the most recent progress in graphene based sensors for mimicking human senses such as artificial retina for image sensors, artificial eardrums, gas sensors, chemical sensors, and tactile sensors. The brain-like processors are discussed based on conventional transistors as well as memristor related neuromorphic computing. The brain-machine interface is introduced for providing a single pathway. Besides, the artificial muscles based on graphene are summarized in the means of actuators in order to react to the physical world. Future opportunities remain for elevating the performances of human-like sensors and their clinical applications.

Low-dimensionality carbon-based biosensors: the new era of emerging technologies in bioanalytical chemistry

Since the last decade, carbon nanomaterials have had a notable impact on different fields such as bioimaging, drug delivery, artificial tissue engineering, and biosensors. This is due to their good compatibility toward a wide range of chemical to biological molecules, low toxicity, and tunable properties. Especially for biosensor technology, the characteristic features of each dimensionality of carbon-based materials may influence the performance and viability of their use. Surface area, porous network, hybridization, functionalization, synthesis route, the combination of dimensionalities, purity levels, and the mechanisms underlying carbon nanomaterial interactions influence their applications in bioanalytical chemistry. Efforts are being made to fully understand how nanomaterials can influence biological interactions, to develop commercially viable biosensors, and to gain knowledge on the biomolecular processes associated with carbon. Here, we present a comprehensive review highlighting the characteristic features of the dimensionality of carbon-based materials in biosensing.

One-Step Template-Free Laser Patterning of Metal Microhoneycomb Structures

Metal microhoneycomb structures have received considerable attention as a type of interaction-efficient functional devices owing to their unique morphology and material properties. Microhoneycomb structures are mainly fabricated using the well-known breath-figure method. However, additional post-treatments are required to produce a metal structure because it is a polymer-based process, and this necessitates expensive, complex, and multi-step fabrication processes. Therefore, a simple, low-cost metal honeycomb fabrication process is necessary. In this paper, the laser patterning of an organometallic solution to produce silver microhoneycomb (Ag microhoneycomb) structures is proposed. Various phenomena such as rapid organic evaporation, silver nanoparticle solidification, and material reorganization from Marangoni flow are found to enable patterning-induced microhoneycomb formation. Parametric studies demonstrate that the pore size can be easily controlled through simple laser parameter changes. In addition, cyclic voltammetry and electrochemical impedance spectroscopy studies confirm the potential electrochemical applications of the Ag microhoneycomb structures based on the variation of electrochemical redox behavior depending on the pore size. Owing to the excellent advantages of one-step laser patterning without any templates, the proposed process will likely promote the practical use of the metal microhoneycomb structures.

Phase Separation of an Evaporating Ternary Solution in a Hele-Shaw Cell

In the present work, we investigate the dynamic phenomena induced by solvent evaporation from ternary solutions confined in a Hele-Shaw cell. The model solutions consist of ethanol, water, and oil, and with the decrease in ethanol concentration by selective evaporation, they may undergo microdroplet formation via the ouzo effect or macroscopic liquid-liquid phase separation. We varied the initial concentration of the three components of the solutions. For all ternary solutions, evaporation of the good solvent ethanol from the gas-liquid interface, aligned with one side of the cell, leads to a Marangoni instability at the early stage of the evaporation process. The presence of the Marangoni instability is in agreement with our recent predictions based on linear stability analysis of binary systems. However, the location and onset of subsequent microdroplet formation and phase separation are the result of the interplay between the Marangoni instability and the initial composition of the ternary mixtures. We classified the ternary solutions into different groups according to the initial concentration of oil. For each group, based on the ternary diagram of the mixture, we offer a rationale for the way phase separation takes place and discuss how the instability influences droplet nucleation. Our work helps us to understand under what conditions and where droplet nucleation can take place when advection is present during phase separation inside a microfluidic device.

Hexameric to Trimeric Lanthanide-Included Selenotungstates and Their 2D Honeycomb Organic-Inorganic Hybrid Films Used for Detecting Ochratoxin A

Two types of organic-inorganic hybrid structure-related lanthanide (Ln)-included selenotungstates (Ln-SeTs) [H₂N(CH₃)₂]₁₁Na₇[Ce₄(H₂PTCA)₂(H₂O)₁₂(HICA)]₂[SeW₄O₁₇]₂[W₂O₅]₄[SeW₉O₃₃]₄·64H₂O (1, H₃PTCA = 1,2,3-propanetricarboxylic acid, H₂ICA = itaconic acid) and [H₂N(CH₃)₂]₆Na₄[Ln₄SeW₈(H₂O)₁₄(H₂PTCA)₂O₂₈] [SeW₉O₃₃]₂·31H₂O [Ln = Pr³⁺ (2), Nd³⁺ (3)] were obtained by Ln nature control. The primary frameworks of 1-3 are composed of trivacant Keggin-type [B-α-SeW₉O₃₃]^8- and [SeW₄O_m]^n- [Ln = Ce³⁺ (1), m = 17, n = 6; Ln = Pr³⁺ (2), Nd³⁺ (3), m = 18, n = 8] fragments bridged by organic ligands and Ln clusters. Intriguingly, Ln nature results in the degradation of hexameric 1 to trimeric 2-3. Besides, 1@DMDSA and 3@DMDSA composites (DMDSA·Cl = dimethyl distearylammonium chloride) were prepared through the cation exchange method, which were then reorganized to form two-dimensional (2D) honeycomb thin films by the breath figure method. Using these honeycomb thin films as electrode materials, the aptasensors were further established by utilizing methylene blue as an indicator and cDNA and Au nanoparticles as signal amplifiers to enhance the response signal so as to realize the purpose of ochratoxin A (OTA) detection. This work provides a new platform for detecting OTA and explores the application potential of POM-based composites in biological and clinical analyses.