Ex vivo performance evaluation of a transdermal gold injectable microneedle for tyrosinase sensing

Here, the semi-invasive direct electrochemical detection of melanoma biomarkers in non-treated skin has been envisaged. The enzyme tyrosinase (TYR) was to be addressed with a microneedle electrochemical sensor. The microneedles were fabricated by polydimethylsiloxane (PDMS) casting with stable polymers. The as-prepared microneedles (MNs) were then coated by gold sputtering. The gold MNs were finally covered by alginate/catechol to provide a liquid electrolyte layer that contained electroactive species, such as catechol, whose redox state can be linked to the concentration of TYR in the skin. The sensor showed high sensitivity of 7.52 µA·mg–1·mL TYR in dummy skin. A relative standard deviation (RSD) of 8.54 % (n=5) demonstrated that the Catechol@alginate: gold MN electrode had excellent reproducibility for continuous glucose detection. Also, five parallel Catechol@alginate: gold MN electrodes were fabricated using the same experimental setup and showed an RSD of 3.95 % (n=5). These results suggest that the electrode fabrication process was reproducible, and Catechol@alginate: gold MN biosensors demonstrated high stability for the repetitive detection of TYR. Furthermore, the sensor has high selectivity in the presence of interfering components towards TYR screening.

False Morphology of Aerogels Caused by Gold Coating for SEM Imaging

The imaging of non-conducting materials by scanning electron microscopy (SEM) is most often performed after depositing few nanometers thick conductive layers on the samples. It is shown in this work, that even a 5 nm thick sputtered gold layer can dramatically alter the morphology and the surface structure of many different types of aerogels. Silica, polyimide, polyamide, calcium-alginate and cellulose aerogels were imaged in their pristine forms and after gold sputtering utilizing low voltage scanning electron microscopy (LVSEM) in order to reduce charging effects. The morphological features seen in the SEM images of the pristine samples are in excellent agreement with the structural parameters of the aerogels measured by nitrogen adsorption-desorption porosimetry. In contrast, the morphologies of the sputter coated samples are significantly distorted and feature nanostructured gold. These findings point out that extra care should be taken in order to ensure that gold sputtering does not cause morphological artifacts. Otherwise, the application of low voltage scanning electron microscopy even yields high resolution images of pristine non-conducting aerogels.

Optimization of a Hydrothermal Growth Process for Low Resistance 1D Fluorine-Doped Zinc Oxide Nanostructures

Design of Experiment (DOE) has been used for the optimization of a hydrothermal growth process of one-dimensional fluorine-doped zinc oxide (1D-FZO). Box-Behnken design was used in the DOE which includes three design points on each of the synthesis condition parameters. The condition parameters were the gold sputtering time (10 s, 15 s, and 20 s), hydrothermal reaction time (3 hours, 6.5 hours, and 10 hours), and hydrothermal temperature (50°C, 75°C, and 100°C). This statistical method of DOE was used to study the effects of these hydrothermal conditions on the quality of 1D-FZO produced. Au nanoparticles were used as the catalyst to enable the growth of the 1D-FZO. The XRD and EDX analysis confirmed the formation of polycrystalline FZO with the presence of fluorine, zinc, and oxygen elements. SEM observations indicated that the sputtering time of the Au nanoparticles has significant effect on the morphology and growth process of 1D-FZO. The lowest resistance value of 22.57 Ω was achieved for 1D-FZO grown with the longest Au sputtering time at growth temperature below 100°C.

Nanotransfer printing of plasmonic nano-pleat arrays with ultra-reduced nanocavity width using perfluoropolyether molds

Ultra-reduced nanocavities in plasmonic nano-pleat arrays achieved by gold sputtering on perfluoropolyether molds and one-step nanotransfer printing.

Templating growth of gold nanostructures with a CdSe quantum dot array

The controlled gold sputtering on quantum dot arrays forms gold nanostructures exclusively on top of quantum dots by self-assembly. A real time observation of the gold nanostructure growth is enabled with grazing incidence small-angle X-ray scattering (GISAXS).

Growth mechanisms of self-assembled gold nanoparticles in Deep Eutectic Solvent

Self-assembled metallic nanoparticles are attractive candidates for plasmonic heating, non-linear optical switching [1], bio-analytical, chemical [2], catalytic , and surface enhanced RAMAN scattering (SERS) [3]. These applications are strongly dependent on the shape, size, composition, size distribution and volume fraction of nanoparticles. Here, self-assembly of gold nanoparticles (AuNPs) was obtained by low energy sputter deposition on Deep Eutectic Solvent (DES ; choline chloride and urea) surfaces and elucidated by Small Angle X-ray Scattering (SAXS), Cryogenic Transmission Electron Microscopy (Cryo-TEM) and UV-Vis. Data analysis shows the formation of spherically shaped AuNPs of 5 nm in diameter with narrow size distributions. Moreover, analysis reveals that prolongation of gold-sputtering time has no effect on the size of the particles and only the concentration of AuNPs increases linearly. The growth of the maxima in evaluated structure factor S(q) and the distance distribution function G(r) at higher concentrations of AuNPs is caused by the interference effects. Moreover, it indicates that the particles are not arranged in random but have a self-assembly in short-range order. Prolonged gold-sputtering time leads to increase in the ordering of the AuNPs with strong interactions. It is proposed that the self-assembly of AuNPs is due to the ionic liquid template effects of DES and the balancing physical forces. Moreover, a disulfide based stabilizer bis ((2-Mercaptoethyl) trimethylammonium) disulfide dichloride was applied to supress the self-assembly. The stabilizer even reverses the self-assembled or agglomerated AuNPs back to stable 5 nm individual particles. The templating effect of DES is compared with the non-templating solvent Castor oil. Our results will also pave a way to understand and control self-assembly of metallic and bimetallic nanoparticles.