Characterization Of Surface Functional Groups Research Articles

Fabrication of Adsorbent Using Nano-Sized Lignocellulosic Biochar Coated on Luffa Aegyptiaca Sponge to Remove Heavy Metal Chromium VI

Eliminating heavy metal Cr (VI) in liquids is challenging. Developing adsorbents using sustainable, cheap, and biodegradable materials is still a concern. Therefore, this study aims to synthesize a heavy metal adsorbent by transforming forest residue into nano-sized lignocellulose biochar. This nano-sized lignocellulosic biochar, with the assistance of chitosan and alginate, was coated onto the Luffa aegyptiaca sponge surface to complete the structure of the proposed heavy metal adsorbent. This adsorbent is easy to apply in adsorbing heavy metals, is durable, and can be reused. The adsorbent products were characterized to observe the functional groups by Fourier Transform Infrared (FTIR) and surface morphology by Scanning Electron Microscopy (SEM). The adsorbents were also experimented with contact times of 120 and 1200 minutes in the adsorption process. The decrease in heavy metal concentration was analyzed by Atomic Absorption Spectroscopy (AAS). Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX) observed the adsorbent surface that has absorbed heavy metal ions. FTIR characterization of surface functional groups showed the presence of hydrogen, aliphatic C-H group, C=C aromatic ring, carboxyl groups, and carbonate ion, capable of binding heavy metal Cr (VI). The morphology of the adsorbent coated on luffa showed that the adsorbent was well attached. The results of the adsorption process showed a decrease in Cr (VI) concentration, with adsorption efficiency reaching 94% for 1200 min and adsorption capacity of 0.36 mg/g. SEM-EDX results validated the attachment of Cr (VI) heavy metal ions to the adsorbent surface.

Preparation and Surface Characterization of Cerium Dioxide for Separation of 68Ge/68Ga and Other Medicinal Radionuclides.

The overall need for the preparation of new medicinal radionuclides has led to the fast development of new sorption materials, extraction agents, and separation methods. Inorganic ion exchangers, mainly hydrous oxides, are the most widely used materials for the separation of medicinal radionuclides. One of the materials that has been studied for a long time is cerium dioxide, a competitive sorption material for the broadly used titanium dioxide. In this study, cerium dioxide was prepared through calcination of ceric nitrate and fully characterized using X-ray powder diffraction (XRPD), infrared spectrometry (FT-IR), scanning and transmission electron microscopy (SEM and TEM), thermogravimetric and differential thermal analysis (TG and DTA), dynamic light scattering (DLS), and analysis of surface area. In order to estimate the sorption mechanism and capacity of the prepared material, characterization of surface functional groups was carried out using acid-base titration and mathematical modeling. Subsequently, the sorption capacity of the prepared material for germanium was measured. It can be stated that the prepared material is prone to exchange anionic species in a wider range of pH than titanium dioxide. This characteristic makes the material superior as a matrix in 68Ge/68Ga radionuclide generators, and its suitability should be further studied in batch, kinetic, and column experiments.

Surface functional groups and degree of carbonization of selected chars from different processes and feedstock.

The knowledge of the structural and chemical properties of biochars is decisive for their application as technical products. For this reason, methods for the characterization of biochars that are generally applicable and allow quality control are highly desired. Several methods that have shown potential in other studies were used to investigate two activated carbons and seven biochars from different processes and feedstock. The chars were chosen to cover a wide range of chemical composition and structural properties as a hardness test for the analytical methods used in this study. Specific problems connected with the pretreatment of samples and drawbacks of some methods for some types of chars could be identified in an integrated consideration of the results from different methods. None of the spectroscopic methods was found to be suitable for the quality control of all types of chars. The most valuable results were obtained by chemical analysis that, however, required the complete determination of the main elements, including that of oxygen, and of inorganic components for adequate results. The combination of X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopy allows a rough characterization of surface functional groups, but cannot discriminate aliphatic and aromatic OH groups. FT-IR might be a suitable method for the quality control of biochars made at lower temperature. The results of Raman spectroscopy did not well correlate with the amount of sp2 hybridized carbon determined by XPS. A better correlation of XPS data was found with the electrical polarization determined by the method of spectral induced polarization that was used for the first time in conjunction with extensive analytical characterization.

Atomically Thin Bilayer Janus Membranes for Cryo-electron Microscopy.

Cryo-electron microscopy (cryo-EM) has emerged as a vital tool to reveal the native structure of beam-sensitive biomolecules and materials. Yet high-resolution cryo-EM analysis is still limited by the poorly controlled specimen preparation and urgently demands a robust supporting film material to prepare desirable samples. Here, we developed a bilayer Janus graphene membrane with the top-layer graphene being functionalized to interact with target molecules on the surface, while the bottom layer being kept intact to reinforce its mechanical steadiness. The ultraclean and atomically thin bilayer Janus membrane prepared by our protocol on one hand generates almost no extra noise and on the other hand reduces the specimen motion during cryo-EM imaging, thus allowing the atomic-resolution characterization of surface functional groups. Using such Janus membranes in cryo-EM specimen preparation, we were able to directly image the lithium dendrite and reconstruct macromolecules at near-atomic resolution. Our results demonstrate the bilayer Janus design as a promising supporting material for high-resolution cryo-EM and EM imaging.

Ammonia plasma-treated electrospun polyacrylonitryle nanofibrous membrane: the robust substrate for protein immobilization through glutaraldhyde coupling chemistry for biosensor application

The surface of polyacrylonitrile electrospun nanofibrous membrane (PAN NFM) was aminated by the ammonia plasma treatment. The content of amine groups has been estimated for different time of plasma treatment. The newly generated amine groups were successfully activated by glutaraldehyde (Ga) for the covalent attachment of the protein molecules on the NFM surface. Bio-functionalization of ammonia plasma treated PAN NFM was carried out by the primary antibodies (Ab) immobilization as a protein model through Ga coupling chemistry. For comparison, the immobilization of Ab was also performed through physical interactions. Attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR) was used for the characterization of surface functional groups of PAN NFM after different modifications. The surface morphology of the NFM after immobilization was characterized using scanning electron microscope (SEM). The efficacy of Ab immobilization was estimated by enzyme-linked immuno sorbent assay (ELISA) method. X- Ray photoelectron spectroscopy (XPS) was performed to confirm the covalent immobilization of Ab on the modified PAN NFM. Results show that ammonia plasma treatment effectively increased the amount of Ab immobilization through Ga coupling chemistry. Our findings suggest that this is a versatile model for the preparation of stable bio-functionalized NFM which is applicable in different field of biomedical science.

Novel Multiparametric Approach to Elucidate the Surface Amine-Silanization Reaction Profile on Fluorescent Silica Nanoparticles

This Article addresses the important issue of the characterization of surface functional groups for optical bioassay applications. We use a model system consisting of spherical dye-doped silica nanoparticles (NPs) that have been functionalized with amine groups whereby the encapsulated cyanine-based near-infrared dye fluorescence acts as a probe of the NP surface environment. This facilitates the identification of the optimum deposition parameters for the formation of a stable ordered amine monolayer and also elucidates the functionalization profile of the amine-silanization process. Specifically, we use a novel approach where the techniques of fluorescence correlation spectroscopy (FCS) and fluorescence lifetime measurement (FL) are used in conjunction with the more conventional analytical techniques of zeta potential measurement and Fourier transfer infrared spectroscopy (FTIR). The dynamics of the ordering of the amine layer in different stages of the reaction have been characterized by FTIR, FL, and FCS. The results indicate an optimum reaction time for the formation of a stable amine layer, which is optimized for further biomolecular conjugation, whereas extended reaction times lead to a disordered cross-linked layer. The results have been validated using an immunoglobulin (IgG) plate-based direct binding assay where the maximum number of IgG-conjugated aminated NPs were captured by immobilized anti-IgG antibodies for the NP sample corresponding to the optimized amine-silanization condition. Importantly, these results point to the potential of FCS and FL as useful analytical tools in diverse fields such as characterization of surface functionalization.

Surface Properties of Carbon

Abstract Carbon surface chemistry is relatively new as an independent subject of inquiry, and, judging by the volume of publications, is receiving increasing attention throughout the world. Our conception of carbon black and its functional behavior has changed significantly since the pioneering publication by Studebaker in 1957. Within the last few years there have been a number of excellent reviews covering various aspects of carbon chemistry by authors who are presently active in this field. Donnet, Puri, and Boehm discuss reactions of carbon and the characterization of surface functional groups while van der Plas is particularly thorough on the subject of adsorption properties and porosity. Deviney explores the relationship between surface chemistry and carbon-elastomer interactions, as does Studebaker from the point of view of the practical application of carbon black in rubber. Current monographs containing useful background information are collected in “Les Carbones” and in Walker's continuing series, “Chemistry and Physics of Carbon”. This review will describe how information from diverse sources has contributed to our understanding of the surface reactivity and fundamental adsorption behavior of carbon. It will be shown that most properties of carbon blacks are consistent with a surface structure wherein large deformed basal layers conforming to the topography of the surface are composed of several planar aromatic domains with functional groups at edge and defect sites. Examples of strong molecular interactions are given which involve specific reaction with the basal surface, individual functional groups, or a combination of both.