Integrating Prussian Blue Analog-Based Nanozyme and Online Visible Light Absorption Approach for Continuous Hydrogen Sulfide Monitoring in Brains of Living Rats.

The continuous detection of hydrogen sulfide (H2S) is significant for revealing its role in the neuron protection and diagnosis of various diseases. In this study, a Prussian blue analog nanocubes (PBA NCs)-based oxidase-like mimic was synthesized and designed for continuous H2S monitoring in a visible light absorption-based online optical detection platform (OODP). A specific chemical reaction between H2S and the PBA NCs induce a decreasing oxidase-like activity of the PBA NCs, generating lower amounts of oxidized products of 3,3'5,5'-tetramethylbenzidine (TMB) and increasing the light intensity. By coupling the microdialysis techniques with OODP, excellent linearity in the range of 0.1-20 µM H2S with a limit of detection of 33 nM and outstanding stability, reproducibility, and specificity in the response to H2S were exhibited. By using this OODP, near real-time response and continuous H2S measurements in the brains of living rats were successfully achieved. This new idea of integrating enzyme-like mimics with specific chemical reactions to form an online optical detection platform for continuous monitoring of neurochemical in the brain may be highly meaningful for thoroughly understanding the function of the brain.

Dual-Channel Online Optical Detection Platform Integrated with a Visible Light Absorption Approach for Continuous and Simultaneous in Vivo Monitoring of Ascorbic Acid and Copper(II) Ions in a Living Rat Brain.

Continuous recording of the dynamic changes of multiple physiologically neurochemicals in vivo is vital to understand the molecular basis of brain functions. For instance, disentangling the complicated interrelationship between ascorbic acid (AA) and copper ions (Cu2+) in signal transduction and homeostasis remains essential in understanding the pathology of hypoxia damage and neurodegenerative diseases. Unfortunately, to the best of our knowledge, there is still no report regarding the development of online and in vivo electrochemical or optical methods that can simultaneously measure AA and Cu2+ due to the limitation of different detection mechanisms and environmental conditions. In this work, we report a parallel dual-channel online optical detection platform (OODP) for the continuous and simultaneous monitoring of AA and Cu2+ in a living rat brain by integrating a capillary-based microfluidic system as well as an optical detector built under a bright-field microscope. Two kinds of colorimetric sensors, oxidized tetramethylbenzidine (oxTMB) and dopamine functionalized silver nanoparticles (DA-AgNPs), were used to recognize AA and Cu2+ in physically isolated detection channels. Combined with in vivo microdialysis sampling, the dual-channel OODP exhibited a wide linearity for AA and Cu2+ detection in the ranges of 0.5 µM to 100 µM and 0.1 µM to 10 µM, respectively. Compared to online electrochemical systems, this dual-channel OODP shows the following advantages: (1) isolated detection positions for two species, which can easily avoid crosstalk, and (2) a small dead-volume of 0.0113 µL in the detector, which obviously improves the time resolution. Along with its high stability, selectivity, and a near real-time response, the constructed dual-channel OODP can be successfully used to monitor cerebral AA and Cu2+ alterations simultaneously in a living rat brain.

Enhanced Visible Light Photocatalytic Decolorization of Methylene Blue by Hierarchical Ternary Nanocomposites Cu-TiO2-Mesoporous-Silica Microsphere.

In this study, hierarchical ternary nanocomposites, i.e., Cu-TiO2-mesoporous silica microspheres (Cu-TiO2-MSM), were synthesized as ternary photocatalyst system to improve the visible light photocatalytic degradation of the environmental pollutant model dye methylene blue (MB). The innovation of this method is in situ depositing TiO2 and Cu2O nanoparticles sequentially onto the surface of mesoporous silica microspheres to form highly active heterostructure. The improved activity for the degradation of MB is attributed to: (1) the high adsorption capacity of the porous and interconnected-channel-structure MSM to MB; (2) the valence band electrons of TiO2 released from the conduction band generating abundant highly active free radicals, which directly reacted with adsorbed MB. The photocatalytic degradation efficiency to MB was found to be 98% in 5 min, and almost 100% in 20 min. This study paves a way for the development of a ternary-doped catalyst for visible light photocatalytic degradation and may exhibit widely application in industry.

Co3O4 nanoparticles anchored on nitrogen-doped reduced graphene oxide as a multifunctional catalyst for H2O2 reduction, oxygen reduction and evolution reaction.

This study describes a facile and effective route to synthesize hybrid material consisting of Co3O4 nanoparticles anchored on nitrogen-doped reduced graphene oxide (Co3O4/N-rGO) as a high-performance tri-functional catalyst for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and H2O2 sensing. Electrocatalytic activity of Co3O4/N-rGO to hydrogen peroxide reduction was tested by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. Under a reduction potential at -0.6 V to H2O2, this constructing H2O2 sensor exhibits a linear response ranging from 0.2 to 17.5 mM with a detection limit to be 0.1 mM. Although Co3O4/rGO or nitrogen-doped reduced graphene oxide (N-rGO) alone has little catalytic activity, the Co3O4/N-rGO exhibits high ORR activity. The Co3O4/N-rGO hybrid demonstrates satisfied catalytic activity with ORR peak potential to be -0.26 V (vs. Ag/AgCl) and the number of electron transfer number is 3.4, but superior stability to Pt/C in alkaline solutions. The same hybrid is also highly active for OER with the onset potential, current density and Tafel slope to be better than Pt/C. The unusual catalytic activity of Co3O4/N-rGO for hydrogen peroxide reduction, ORR and OER may be ascribed to synergetic chemical coupling effects between Co3O4, nitrogen and graphene.