Evaluation of Physico-Chemical Characteristics of Cement Superplasticizer Based on Polymelamine Sulphonate.

Cementitious materials are used to construct an engineered barrier in repositories for radioactive waste. The cement matrix may contain a variety of organic compounds, some of which are polymeric admixtures used as plasticizers. Superplasticizers (SPs) are highly effective organic cement additives for reducing water amount, increasing workability, homogeneity, plasticity and the non-segregation of mortars and grouts, improving mechanical properties and resistance to destructive environments.

Epitaxial Lateral Overgrowth of GaN on a Laser-Patterned Graphene Mask.

Epitaxial lateral overgrowth (ELO) of GaN epilayers on a sapphire substrate was studied by using a laser-patterned graphene interlayer. Monolayer graphene was transferred onto the sapphire substrate using a wet transfer technique, and its quality was confirmed by Raman spectroscopy. The graphene layer was ablated using a femtosecond laser, which produced well-defined patterns without damaging the underlying sapphire substrate.

Green Removal of DUV-Polarity-Modified PMMA for Wet Transfer of CVD Graphene.

To fabricate graphene-based high-frequency electronic and optoelectronic devices, there is a high demand for scalable low-contaminated graphene with high mobility. Graphene synthesized via chemical vapor deposition (CVD) on copper foil appears promising for this purpose, but residues from the polymethyl methacrylate (PMMA) layer, used for the wet transfer of CVD graphene, drastically affect the electrical properties of graphene. Here, we demonstrate a scalable and green PMMA removal technique that yields high-mobility graphene on the most common technologically relevant silicon (Si) substrate.

MOVPE Growth of GaN via Graphene Layers on GaN/Sapphire Templates.

The remote epitaxy of GaN epilayers on GaN/sapphire templates was studied by using different graphene interlayer types. Monolayer, bilayer, double-stack of monolayer, and triple-stack of monolayer graphenes were transferred onto GaN/sapphire templates using a wet transfer technique. The quality of the graphene interlayers was examined by Raman spectroscopy.

Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy for Probing Riboflavin on Graphene.

Graphene research and technology development requires to reveal adsorption processes and understand how the defects change the physicochemical properties of the graphene-based systems. In this study, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and graphene-enhanced Raman spectroscopy (GERS) coupled with density functional theory (DFT) modeling were applied for probing the structure of riboflavin adsorbed on single-layer graphene substrate grown on copper. Intense and detailed vibrational signatures of the adsorbed riboflavin were revealed by SHINERS method.

Gold Nanoparticles Generated Using the Nanosecond Laser Treatment of Multilayer Films and Their Use for SERS Applications.

Surface-enhanced Raman spectroscopy (SERS) substrates fabricated using a repeated laser treatment of thin gold films are demonstrated. The presented SERS substrates consist of the gold nanoparticles, whose density and size depend on the used film thickness and number of treated films. The larger number of the treated gold film layers increases the amount of larger nanoparticles (size >20 nm).

Shell-isolated nanoparticle-enhanced Raman spectroscopy for characterization of living yeast cells.

Studying the biochemistry of yeast cells has enabled scientists to understand many essential cellular processes in human cells. Further development of biotechnological and medical progress requires revealing surface chemistry in living cells by using a non-destructive and molecular structure sensitive technique. In this study shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was applied for probing the molecular structure of Metschnikowia pulcherrima yeast cells.

Crowding enhances lipase turnover rate on surface-immobilized substrates.

Utilizing surface-immobilized synthetic lipid substrates containing the redox-active ferrocene groups, the enzymatic activity of lipase from Thermomyces lanuginosus was measured by the cyclic voltammetry method. The activity was correlated with the surface density of the protein by the ATR-IR spectroscopy and the total internal reflection ellipsometry. It was found that the lipase turnover rate significantly increases with its surface density.

Effect of potential on temperature-dependent SERS spectra of neuromedin B on Cu electrode.

Adsorption of decapeptide neuromedin B (NMB) on copper electrode has been investigated by in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry in the temperature interval from 12 to 72 °C at -0.600 and -1.000 V potentials.

Potential induced changes in neuromedin B adsorption on Ag, Au, and Cu electrodes monitored by surface-enhanced Raman scattering.

Surface-enhanced Raman scattering (SERS), electrochemistry, and generalized two-dimensional correlation analysis (G2DCA) methods were used to define neuromedin B (NMB) ordered superstructures on Ag, Au, and Cu electrode surfaces at different applied electrode potentials in an aqueous solution at physiological pH. The orientation of NMB and the adsorption mechanism were determined based on the analysis of enhancement, broadness, and shift in wavenumber of particular bands, which allow drawing some conclusions about NMB geometry and changes in this geometry upon change of the electrode type and applied electrode potential. The presented data demonstrated that NMB deposited onto the Ag, Au, and Cu electrode surfaces showed bands due to vibrations of the moieties that were in contact/close proximity to the electrode surfaces and thus were located on the same side of the polypeptide backbone.

Structure of functional Staphylococcus aureus alpha-hemolysin channels in tethered bilayer lipid membranes.

We demonstrate a method for simultaneous structure and function determination of integral membrane proteins. Electrical impedance spectroscopy shows that Staphylococcus aureus alpha-hemolysin channels in membranes tethered to gold have the same properties as those formed in free-standing bilayer lipid membranes. Neutron reflectometry provides high-resolution structural information on the interaction between the channel and the disordered membrane, validating predictions based on the channel's x-ray crystal structure.

Computational Modeling of the Electrochemical System of Lipase Activity Detection.

This paper presents computational modeling of response kinetics of bioelectroanalytical system based on solid supported lipase substrate and lipase interaction. The model assumes that lipase substrate is formed by dripping and drying a small amount of the ethanol solution of 9-(5'-ferrocenylpentanoyloxy)nonyl disulfide (FPONDS) and that lipase is capable of cleaving FPONDS ester bonds via hydrolysis mechanism. Two mathematical models have been developed and evaluated trough computational simulation series by comparing them to experimental data.

Probing of lipase activity at air/water interface by sum-frequency generation spectroscopy.

The infrared-visible sum-frequency generation (SFG) vibrational spectroscopy was used to probe enzymatic activity of Thermomyces lanuginosus lipase (TLL) at air/water interface. A monolayer of amphiphilic O-palmitoyl-2,3-dicyanohydroquinone (PDCHQ), containing target ester group and two CN groups serving as vibrational markers, was utilized as an enzyme substrate. SFG data revealed the detailed molecular scale structure and properties of the PDCHQ layer at the interface.

Electrochemical method for the detection of lipase activity.

A novel electrochemical technique for the general assay of lipase activity is described. The method utilizes a solid-supported lipase substrate, which is formed by dripping and drying a small amount of an ethanol solution of 9-(5'-ferrocenylpentanoyloxy)nonyl disulfide (FPONDS) onto gold modified by a hexanethiol self-assembled monolayer. The redox ferrocene group of FPONDS generates the electrochemical signal, the intensity of which is proportional to the number of FPONDS molecules at the interface.