Neurotransmitter Assay for In Vivo Nerve Signal Detection Using Bismuth Immobilized on a Carbon Nanotube Paste Electrode.

BACKGROUND: Voltammetric analysis of the neurotransmitter epinephrine (EP) was performed using bismuth immobilized on a carbon nanotube paste electrode (BCE), whose properties were compared with those of a carbon nanotube paste electrode (CE). BCE was found to be more efficient in detecting EP. METHODS: The analytical parameters used were 0.3 V square-wave (SW) stripping voltammetric amplitude, 400 Hz frequency, -0.8 V initial potential, and 0.015 V increment potential. The optimized conditions were applied to an assay of a carp's front fin. RESULTS: A BCE was inserted into a carp's front fin muscle, and a stimulus was given every 50 s. This circuit is easy to use and does not require much analytical preparation time. CONCLUSIONS: The working electrode is miniscule, and its detection limit is very low. The in vivo muscle's chronoamperometric nerve currents were analyzed. These results have potential for applications in medical diagnostics, pharmaceuticals, interface controllers, and other fields.

Trace assay of insulin in a pharmacy drug with a paste electrode.

This paper describes the development of a voltammetric assay of insulin using a DNA immobilized onto a carbon nanotube paste electrode (CNPE), the peak potential of which was 0.2 V, vs. Ag/AgCl on the CNPE. The cyclic voltammetry (CV) and square-wave (SW) stripping voltammetry parameters of the optimized conditions were determined. Low analytical working ranges of 10-80 ugL-1 CV and 0.01-0.1 ngL-1 SW were attained. The precision of the insulin concentration of 0.01 ugL-1 was 0.14 (n = 15) RSD using the optimum conditions, in which the detection limit was 0.004 ngL-1 (6.9 × 10-12 M) (S/N = 3) using only an accumulation time of 400 s. The developed method was applied to determine insulin in a pharmacy drug from analytical-grade chemicals (from Aldrich).

An Accessible Integrated Nanoparticle in a Metallic Hole Structure for Efficient Plasmonic Applications.

Addressing the severe deterioration of gap mode properties in spherical-shaped nanoparticles (NPs) becomes necessary due to their utilization in a wide range of multi-disciplinary applications. In this work, we report an integrated plasmonic nanostructure based on a spherical-shaped nanoparticle (NP) in a metallic hole as an alternative to a NP-only structure. With the help of three-dimensional (3D) electromagnetic simulations, we reveal that when a NP is positioned on the top of a metallic hole, it can exhibit superior gap-mode-based local-field intensity enhancement. The integrated nanostructure displayed a ~22-times increase in near-field enhancement characteristics, similar to cube- or disk-shaped nanostructure's plasmonic properties. From an experimental perspective, the NP positioning on top of the metallic hole can be realized more easily, facilitating a simple fabrication meriting our design approach. In addition to the above advantages, a good geometrical tolerance (metallic hole-gap size error of ~20 nm) supported by gap mode characteristics enhances flexibility in fabrication. These combined advantages from an integrated plasmonic nanostructure can resolve spherical-shaped NP disadvantages as an individual nanostructure and enhance its utilization in multi-disciplinary applications.

Enhancement of the response time in organic photorefractive composites using alkoxy-substituted PDCST as a nonlinear optical chromophore: publisher's note.

This publisher's note contains corrections to Opt. Lett.45, 6767 (2020)OPLEDP0146-959210.1364/OL.409743.

Enhancement of the response time in organic photorefractive composites using alkoxy-substituted PDCST as a nonlinear optical chromophore.

The ease of the molecular orientation of a chromophore has an important effect on the electro-optical (EO) properties of polymeric photorefractive (PR) composites. A derivative of 4-piperidinobenzylidene-malononitrile (PDCST) with an alkoxy group added as a side branch was synthesized to improve the molecular orientation characteristics. Electrophoresis was performed on the polymeric PR composite to which the improved PDCST had been added. The optical properties and response times were examined to evaluate the effects of the substitution of the alkoxy group. PDCST substituted with the alkoxy group showed enhanced EO properties and a PR grating formation rate.

Fast photorefractive response in polymeric composites enabled by the control of chromophore free volume.

The molecular orientation of a chromophore importantly affects the electro-optic characteristics of polymeric photorefractive composites. We designed methyl, ethyl, and isopropyl derivatives of 4-piperidinobenzylidene-malononitrile (PDCST) with the aim of enhancing molecular orientation properties, and investigated the effects of alkyl substitution on the electro-optic properties and response times of polymeric photorefractive composites. The three alkyl-substituted PDCSTs showed enhanced electro-optic responses and photorefractive grating buildup rates.

Modulatory Functionalization of Gold Nanorods Using Supramolecular Assemblies.

Supramolecular-assembly-mediated functionalization of gold nanorods (GNRs) has been developed by reversible phase transfer between water and oils, which offers a facile method for fabricating robust GNRs with surface-charge tunability. In this regard, trimethylammonium (TMA) GNRs were initially prepared from conventional cetyltrimethylammonium bromide (CTAB) GNRs by means of a ligand-exchange reaction in the presence of an excess amount of TMA ligands. To further expand their functionality and potential applications, electrostatic assemblies of positively charged TMA-GNRs with negatively charged oleate ions were prepared. These assemblies (OA-GNRs) can undergo facile phase transfer from water to hexane. Interestingly, the reversible electrostatic assembly between the TMA and OA ions fabricated onto GNRs can be easily disrupted by treatment with HCl, which removes the OA ions from the GNRs to re-form the TMA-GNRs, which can be made soluble in aqueous media again. In addition, OA-GNRs can be further used for the synthesis of negatively charged GNRs such as 11-mercaptoundecanoic acid (MUA) GNRs, which are hard to prepare directly from CTAB-GNRs. This versatile method for phase transfer and functionalization on GNRs is expected to broaden the scope of their applications in sensing, biomedical imaging, photothermal therapies, and drug delivery systems.

Lateral photovoltaic effect in flexible free-standing reduced graphene oxide film for self-powered position-sensitive detection.

Lightweight, simple and flexible self-powered photodetectors are urgently required for the development and application of advanced optical systems for the future of wearable electronic technology. Here, using a low-temperature reduction process, we report a chemical approach for producing freestanding monolithic reduced graphene oxide papers with different gradients of the carbon/oxygen concentration ratio. We also demonstrate a novel type of freestanding monolithic reduced graphene oxide self-powered photodetector based on a symmetrical metal-semiconductor-metal structure. Upon illumination by a 633-nm continuous wave laser, the lateral photovoltage is observed to vary linfearly with the laser position between two electrodes on the reduced graphene oxide surface. This result may suggest that the lateral photovoltaic effect in the reduced graphene oxide film originates from the built-in electric field by the combination of both the photothermal electric effect and the gradient of the oxygen-to-carbon composition. These results represent substantial progress toward novel, chemically synthesized graphene-based photosensors and suggest one-step integration of graphene-based optoelectronics in the future.

Enhanced photorefractive performance of polymeric composites through surface plasmon effects of gold nanoparticles.

We investigated the photorefractivity enhancement of polymeric composites by introducing gold nanoparticles (NPs). The gold NPs enhance the photocharge generation rate of sensitizers through plasmon resonance coupling achieved between NPs and sensitizers. Systematic studies show that the presence of gold NPs has increased photocharge generation efficiency, photoconductivity, diffraction efficiency, refractive index modulation, and photorefractive (PR) grating formation rate. The gold-NP-doped PR sample exhibits 2 times larger photocharge generation efficiency and photoconductivity, and 2.5 times faster PR grating formation rate compared to the control sample without the NPs.

A simple method for fabricating a Mach-Zehnder type waveguide using sol-gel derived photopatternable hybrid materials for optical biosensors.

In this work, we report on a simple method to fabricate a Mach-Zehnder type waveguide pattern using photopatternable sol-gel organic-inorganic hybrid materials. The refractive indices and propagation losses of the gel films were measured using the prism coupling method. The refractive indices of the resulting films were significantly influenced by the 3-trimethoxysilylpropylmethacrylate (TMSPM) concentration, and the average propagation loss was 0.32-0.52 dB/cm at the wavelength of 632.8 nm. The waveguides were fabricated using spin-coating and a photolithography technique. The Y-branch and straight pattern of the Mach-Zehnder waveguide were well-defined and had high transparency (> 97%) in the visible region. The average thickness of the gel films was 10 microm, and the average width of the Mach-Zehnder pattern was 10 microm. The structural and optical properties of the fabricated patterns were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), near-infrared (IR) spectroscopy, and ultraviolet (UV)-visible spectroscopy.

Influence of donor moiety in ruthenium sensitizers on the properties of dye-sensitized solar cells.

Heteroleptic ruthenium complexes cis-[Ru(H2dcbpy)(L)(NCS)2], where H2dcbpy is 4,4'-dicarboxylic acid-2,2'-bipyridine and L is 4-(4-(N,N-di-(p-hexyloxyphenyl)-amino)styryl)-4'-methyl-2,2'-bipyridine (Rut-A) or 4-(4'-(3,6-dihexyloxycarbazole-9-yl)-styryl)-4'-methyl-2,2'-bipyridine (Rut-B), have been synthesized and characterized by NMR, UV-Vis spectroscopy, and cyclic voltammogram. The effect of different electron donors on the properties of dye-sensitized solar cells has been studied. The power conversion efficiency of DSSC based on Rut-B is 6.1% while Rut-A delivered a lower efficiency of 4.52% under the same device fabrication and measuring conditions. The better photovoltaic performance of Rut-B is mainly associated with enhanced dye absorptivity and charge recombination suppression.

Tunable color filter with surface plasmon resonance using organic photorefractive composite.

We report on a tunable color filter with surface plasmon resonance (SPR), excited by a photorefractive (PR) diffraction grating. When a white light was incident at the diffraction grating formed by a PR effect, the SPR generated at a metal-dielectric material interface was absorbed, and the reflected light showed a complementary color. When the period of the PR diffraction grating was modified by alteration of the optic configuration, the wavelength at which the SPR excitation led to a reflection minimum changed and the spectrum of the reflected light also changed. A well-known equation was used to help us understand the experimental results. All experimental results are in good agreement with the calculation predictions. This result could lead to a new type of tunable color filter.