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We report the improvement in the sensing performance of electrolyte-gated graphene field-effect transistor (FET) sensors capable of detecting tau protein through a simplified, linker-free, anti-tau antibody immobilization process. For most of the graphene-based immunosensor, linkers, such as pyrenebutanoic acid, succinimidyl ester (PSE) must be used to the graphene surface, while the other side of linkers serves to capture the antibodies that can specifically interact with the target biomarker. In this study, graphene was patterned into eight different types and linker-free patterned graphene FET sensors were fabricated to verify their detection performance. The linker-free antibody immobilization to patterned graphene exhibited that the antibody was immobilized to the edge defect and had a doping-like behaviors on graphene. As the tau protein concentration in the electrolyte increased from 10 fg/ml to 1 ng/ml, the performances, charge neutral point shift and current change rate of the patterned graphene sensors without linkers were enhanced 2–3 times compared to a pristine graphene sensor with the PSE linker. Moreover, tau protein in the plasma of five Alzheimer's disease patients was measured using a linker-free patterned graphene sensor. It shows a 3–4 times higher current change rate than that of pristine graphene sensor with the PSE linker. Since the antibody is immobilized directly without a linker, a patterned graphene sensor without a linker can operate more sensitively in higher ionic concentration electrolyte.

We propose a novel wallpapering-inspired strategy to create wrinkles in a desired location and direction of single-layer graphene (Gr). The key to controlling the wrinkles is to regulate the permeation and release of solution through a regular array of holes between the substrate surface and Gr-based thin membrane (Gr/Cu in the first stage and Gr in the second stage). Microscopic analysis showed that neighboring holes were interconnected by straightened wrinkles with a width of 300–500 nm and height of 10–20 nm, while surface corrugations (e.g., ripples and wrinkles) were suppressed on the planar regions surrounded by wrinkles. Wrinkling mechanism was further verified by in-situ optical microscopy and comparative analysis of Gr/Cu ripples and Gr wrinkles. Our approach is simple yet universally applicable to diverse types of thin membranes, thereby offering a robust and versatile route to engineering properties of atomically thin materials.

Zn-polar (0001) surfaces are more chemically reactive than other surfaces of ZnO crystals and drive preferential anisotropic and asymmetric growth along the [0001] direction, which facilitates growth of c-axis oriented, one-dimensional ZnO nanostructures. Accordingly, capping the top (0001) surface of ZnO crystals can impede c-axis growth and thus serve to modulate growth habits. In this study, we generated vertically aligned ZnO hexagonal nanotube-rod (h-NTR) hybrids by modulating growth habits during a second-stage process. Electron microscopy studies revealed the formation of very thin (10–20 nm) single-crystalline nanotube walls along the edges of underlying hexagonal rod tops capped with Si. In addition, spatially resolved investigation of ZnO h-NTR indicated an abrupt increase in the measured bandgap across rod-tube junctions, which was ascribed to a quantum confinement effect and Burstein–Moss effect of carriers within the very thin nanotube walls.

Graphene has been intensively studied for applications to high-performance sensors, but the sensing characteristics of graphene devices have varied from case to case, and the sensing mechanism has not been satisfactorily determined thus far. In this review, we describe recent progress in engineering of the defects in graphene grown by a silica-assisted chemical vapor deposition technique and elucidate the effect of the defects upon the electrical response of graphene sensors. This review provides guidelines for engineering and/or passivating defects to improve sensor performance and reliability.

A microfluidization and solvent evaporation method was employed to prepare poly(methyl methacrylate) (PMMA) nanoparticles containing coenzyme Q10. Dynamic light scattering and transmission electron microscopy showed that the mean diameter of the nanoparticles was highly influenced by the kind of surfactants used and the recycling number of the microfluidization process. Particles with sizes from 40 to 260 nm and low polydispersities were produced with good reproducibility. Despite a very high target drug loading yield, 38.7% (w/w), the actual loading efficiency reached above 95%, as demonstrated by 1H NMR analysis. Coenzyme Q10 formed a crystal structure within the polymer matrix with a melting temperature of 48 °C, as demonstrated by differential scanning calorimetry. No free drug crystals were found in the aqueous suspension of nanoparticles. A comparative study on structural stability of coenzyme Q10 showed that both UV and high temperature-induced drug inactivation were effectively hindered when the drug was encapsulated within the polymer nanoparticles.

An easy method of measurement of the zeta potentials of sub-50-nm polymeric nanoparticles is suggested. Although zeta potential measurements of nanoparticles or emulsions above 50 nm have been successfully carried out, zeta potentials of emulsions or nanoparticles below 50 nm could not be precisely measured in the region of extremely low conductivity by conventional electrophoresis with a He-Ne laser. However, zeta potentials of sub-50-nm nanoparticles were measured in the region of thin electrical double layers by addition of sodium chloride and zeta potentials in the condition without sodium chloride could be predicted by extrapolation of the measured potentials. The electrophoretic mobility of 150-nm nanoparticles stabilized with sodium dodecylsulfate was the same as that calculated from extrapolation of the measured ones. The zeta potentials of sub-50-nm nanoparticles stabilized with sodium dodecylsulfate could be calculated by the same procedure.