Facile Pretreatment of Three-Dimensional Graphene through Electrochemical Polarization for Improved Electrocatalytic Performance and Simultaneous Electrochemical Detection of Catechol and Hydroquinone

Three-dimensional graphene (3DG) with macroporous structure has great potential in the field of electroanalysis owing to a large active area, excellent electron mobility and good mass transfer. However, simple and low-cost preparation of 3DG electrodes with high electrocatalytic ability is still a challenge. Here, a fast and convenient electrochemical polarization method is established to pretreat free-standing 3DG (p-3DG) to offer high electrocatalytic ability. 3DG with monolithic and macroporous structure prepared by chemical vapor deposition (CVD) is applied as the starting electrode. Electrochemical polarization is performed using electrochemical oxidation (anodization) at high potential (+6 V) followed with electrochemical reduction (cathodization) at low potential (−1 V), leading to exposure of edge of graphene and introduction of oxygen-containing groups. The as-prepared p-3DG displays increased hydrophilicity and improved electrocatalytic ability. As a proof of concept, p-3DG was used to selective electrochemical detection of two isomers of benzenediol, hydroquinone (p-BD) and catechol (o-BD). In comparison with initial 3DG, p-3DG exhibits increased reversibility of redox reaction, improved peak current and good potential resolution with high potential separation between p-BD and o-BD. Individual or selective determination of p-BD or o-BD in single substance solution or binary mixed solution is realized. Real analysis of pond water is also achieved.

Preparation of spheres based on NiO using cation with gel and macroporous structure

The article discusses the production of materials based on nickel oxide in the form of spherical granules ranging in size from 300 to 700 nm, by the method of thermal destruction of cation exchangers with gel (TOKEM-100)and macroporous (TOKEM-250) structures saturated with nickel (II) ions. Thermal analysis was used to establish the temperature regimes of annealing of Ni2+–ТОКЕМ-250 и Ni2+–ТОКЕМ-100 samples. The prepared materials were investigated by XRD and SEM. The use of TOKEM-100 cation exchanger makes it possible to obtain samples with spherical granules based on trigonal nickel (II) oxide, characterized by a sintered surface morphology. The use of TOKEM-250 cation exchanger leads to the formation of spheres based on NiO cubic modification with an inhomogeneous surface morphology.

SYNTHESES OF CATION EXCHANGER WITH MACROPOROSITY AND INVESTIGATING SPECIFIC PROPERTIES

Obtained new strongly acid cation exchanger of macroporous structure based on furfural and dipheniloxide. The optimal amount of the poreformed agent and the molar ratio of the reacting substances were determined. Initially results showed that the polymer matrix using camphor as pore forming agent present a uniform surface with inter-connected pores and adding camphor into the polymer matrix could attain more abundant pores than adding n-heptane. We studied the components, surface and pore structures of the сation exchanger by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). SEM observations showed that the resin abounded in macropores as large as 7.4 to 22.6 µm both in the surface and the interior. The parameters of the porous structure of the samples are calculated using by equation BET (Brauner., at al.) and the total pore volume of ion exchangers and the radius of submicroscopic capillaries were determined. Finally dates testing prototypes under application conditions, allow us to recommend this cation exchanger for sorption of small radius ions at high speed, as fundamentals upon receipt of ion exchangers, etc.

Cryostructuring of Polymeric Systems †: Application of Deep Neural Networks for the Classification of Structural Features Peculiar to Macroporous Poly(vinyl alcohol) Cryogels Prepared without and with the Additives of Chaotropes or Kosmotropes

Macroporous poly(vinyl alcohol) cryogels (PVACGs) are physical gels formed via cryogenic processing of polymer solutions. The properties of PVACGs depend on many factors: the characteristics and concentration of PVA, the absence or presence of foreign solutes, and the freezing-thawing conditions. These factors also affect the macroporous morphology of PVACGs, their total porosity, pore size and size distribution, etc. In this respect, there is the problem with developing a scientifically-grounded classification of the morphological features inherent in various PVACGs. In this study PVA cryogels have been prepared at different temperatures when the initial polymer solutions contained chaotropic or kosmotropic additives. After the completion of gelation, the rigidity and heat endurance of the resultant PVACGs were evaluated, and their macroporous structure was investigated using optical microscopy. The images obtained were treated mathematically, and deep neural networks were used for the classification of these images. Training and test sets were used for their classification. The results of this classification for the specific deep neural network architecture are presented, and the morphometric parameters of the macroporous structure are discussed. It was found that deep neural networks allow us to reliably classify the type of additive or its absence when using a combined dataset.