A novel and highly selective electrochemical sensing platform (ZnCl₂-CF/GCE) based on combination of kiwi skin and zinc chloride nanoparticles was developed for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The constructed electrode shows a high surface area and micro-mesoporous structure. And the electrochemical behaviors of the electrode were further explored by cyclic voltammetry (CV), impedance analysis (EIS), and differential pulse voltammetry (DPV). Under the optimal conditions, the ZnCl₂-CF provides a high sensitivity and selective signaling in the co-existence system of AA, DA, and UA with linear response ranges of 0.05-200 μM, 2-2000 μM, and 1-2500 μM, respectively. The detection limits (S/N = 3) were calculated to be 0.02 μM, 0.16 μM, and 0.11 μM, respectively. In addition, the method has been successfully applied to determine AA, DA, and UA in real samples, which provides potential applications in further sensing study.

A novel electrochemical sensor using the molecularly imprinted (MIP) oxygen-containing polypyrrole (PPy) decorated carbon nanotubes (CNTs) composite was proposed for in vivo detection of dopamine (DA). The prepared sensor exhibits a remarkable sensitivity of (16.18μA/μM) with a linear range of 5.0×10(-11)-5.0×10(-6)M and limit of detection as low as 1.0×10(-11)M in the detection of DA, which might be due to the plenty cavities for binding DA through π-π stacking between aromatic rings and hydrogen bonds between amino groups of DA and oxygen-containing groups of the novel PPy.

The ability to tune the microstructures, bandgap, conductance, chemical environment and thermal storage of carbon nanomaterials such as carbon nanotubes, graphene and fullerenes by optical modulation or response is important to design and fabricate advanced optoelectronic nanodevices. This review is focused on optical control and regulation of structures, properties, interface and interaction of a new generation of photo-responsive carbon nanomaterials/azobenzene moieties (Carbon-AZO) hybrids. The optical switching properties of Carbon-AZO hybrids resulting from the photo-isomerization between trans and cis isomers are highlighted and discussed in terms of photo-energy conversion devices including switches, sensors, detectors, fuels and storage. A wide range of advanced energy conversion devices using Carbon-AZO hybrids can be developed in the future by the optimization of the chemical structure, steric conformation, electrostatic environment and functionalization of specific molecules.

Graphene, a single-atom-thick monolayer of sp(2) carbon atoms perfectly arranged in a honeycomb lattice, is an emerging sensing material because of its extraordinary properties, such as exceptionally high specific surface area, electrical conductivity, and electrochemical potential window. In this study, we demonstrate that three-dimensional (3D), macroporous, highly conductive, and monolithic graphene foam synthesized by chemical vapor deposition represents a novel architecture for electrochemical electrodes. Being employed as an electrochemical sensor for detection of dopamine, 3D graphene electrode exhibits remarkable sensitivity (619.6 μA mM(-1) cm(-2)) and lower detection limit (25 nM at a signal-to-noise ratio of 5.6), with linear response up to ∼25 μM. And the oxidation peak of dopamine can be easily distinguished from that of uric acid - a common interferent to dopamine detection. We envision that the graphene foam provides a promising platform for the development of electrochemical sensors as well as other applications, such as energy storage and conversion.

A simple and effective strategy was proposed for synthesis of AuNPs@polyaniline (AuNPs@PANI) core-shell nanocomposites. AuNPs@PANI nanocomposites were prepared by one-step chemical oxidative polymerization of aniline using chloroaurate acid as the oxidant and AuNPs as the seeds. The synthesized AuNPs@PANI nanocomposites were characterized with transmission electron microscope and UV-vis absorption spectra. Cyclic voltammetric experiments indicated that AuNPs@PANI nanocomposites showed excellent electroactivity in neutral and even alkaline solution. The obtained AuNPs@PANI nanocomposites-modified electrode was fabricated to simultaneously determine dopamine (DA) and ascorbic acid (AA) by differential pulse voltammetry. The separation between the two peak potentials of DA and AA oxidation is 236 mV. The catalytic peak currents were linearly with the concentrations of DA and AA in the range of 10-1700 and 20-1600 μM with correlation coefficients of 0.9997 and 0.9998, respectively. The detection limits for DA and AA were 5 and 8 μM, respectively.

In this study, graphene oxide nanoribbons (GONRs) were synthesized from the facile unzipping of multiwalled carbon nanotubes (MWCNTs) with the help of microwave energy. A core-shell MWCNT/GONR-modified glassy carbon (MWCNT/GONR/GC) electrode was used to electrochemically detect ascorbic acid (AA), dopamine (DA), and uric acid (UA). In cyclic voltammograms, the MWCNT/GONR/GC electrode was found to outperform the MWCNT- and graphene-modified GC electrodes in terms of peak current. For the simultaneous sensing of three analytes, well-separated voltammetric peaks were obtained using a MWCNT/GONR/GC electrode in differential pulse voltammetry measurements. The corresponding peak separations were 229.9 mV (AA to DA), 126.7 mV (DA to UA), and 356.6 mV (AA to UA). This excellent electrochemical performance can be attributed to the unique electronic structure of MWCNTs/GONRs: a high density of unoccupied electronic states above the Fermi level and enriched oxygen-based functionality at the edge of the graphene-like structures, as revealed by X-ray absorption near-edge structure spectroscopy, obtained using scanning transmission X-ray microscopy.

A kinetic study of the C.I. Acid Yellow 9 photooxidative decolorization process, using H(2)O(2) as oxidant, was carried out by chemometric analysis of the UV-visible data recorded during the process. The number of chemical species involved in the photooxidative decolorization process was established by singular value decomposition (SVD) and evolving factor analysis (EFA). Information about the different chemical species along the process was obtained from the spectral and concentration profiles recovered by soft multivariate curve resolution with alternating least squares (MCR-ALS). This information was complemented by mass spectrometry (MS) to postulate a reaction pathway. The dye photooxidative decolorization process involved consecutive and parallel reactions. The consecutive pathway consists of a first stage of dye oxidation followed by the rupture of the azo linkage to form smaller molecules that are degraded in a subsequent stage. The parallel reactions form products that are undetectable in the UV-visible spectra. Kinetic constants of the reactions postulated in the photooxidative process were retrieved by applying a hybrid hard and soft MCR-ALS resolution. All constants were similar for the consecutive stages and higher than those obtained for the parallel reactions.

In this study, a graphene/Pt-modified glassy carbon (GC) electrode was created to simultaneously characterize ascorbic acid (AA), dopamine (DA), and uric acid (UA) levels via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). During the preparation of the nanocomposite, size-selected Pt nanoparticles with a mean diameter of 1.7 nm were self-assembled onto the graphene surface. In the simultaneous detection of the three aforementioned analytes using CV, the electrochemical potential differences among the three detected peaks were 185 mV (AA to DA), 144 mV (DA to UA), and 329 mV (AA and UA), respectively. In comparison to the CV results of bare GC and graphene-modified GC electrodes, the large electrochemical potential difference that is achieved via the use of the graphene/Pt nanocomposites is essential to the distinguishing of these three analytes. An optimized adsorption of size-selected Pt colloidal nanoparticles onto the graphene surface results in a graphene/Pt nanocomposite that can provide a good platform for the routine analysis of AA, DA, and UA.