Inverted organic solar cells enhanced by grating-coupled surface plasmons and waveguide modes.

In this study, we demonstrate improved photovoltaic properties in inverted organic thin-film solar cells by simultaneous excitation of grating-coupled surface plasmons and grating-coupled waveguide modes on gold grating surfaces. The cell consists of a glass-ITO substrate/titanium dioxide/poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/gold structure. The grating structures were fabricated on P3HT:PCBM layers using a nanoimprinting technique with a PDMS stamp. The grating-structured PDMS stamps were fabricated using a DVD-R grating template with a grating pitch, Λ, of 740 nm. Reflectivity measurements made using p-polarized light clearly indicate 2 types of excitation modes, i.e., surface plasmons and waveguide modes, while s-polarized light produces only waveguide modes. Incident photon-to-current efficiency measurements exhibited increased photocurrent wavelengths corresponding to the wavelengths of surface plasmon excitations and waveguide mode excitations. Through the simultaneous excitation of surface plasmons and waveguide modes, short-circuit photocurrents in the grating-structured cells exhibited an improvement of up to 11% in the solar cells, leading to an efficiency increase of 16%.

Effect of urchin-like gold nanoparticles in organic thin-film solar cells.

In this study, urchin-like gold nanoparticles (UL-AuNPs) are used in the fabrication of organic thin-film solar cells (OSCs). UL-AuNPs, which have gold nanothorns on their surface, enhance light accumulation by acting as light-trapping materials. This is due to the enhanced electric field and light scattering attributed to the nanothorns on the surface of the nanoparticles. UL-AuNPs were incorporated into a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ( PEDOT: PSS) thin-film layer of organic thin-film solar cells (OSCs). UV-vis spectra, atomic force microscopy (AFM) images, current density versus voltage properties, and the impedance spectra of the fabricated devices were recorded at various concentrations of UL-AuNPs. We found that the efficiency of the OSCs with UL-AuNPs was not only higher than that of a reference cell without nanoparticles but also higher than that of OSCs with spherical AuNPs. Finite-difference time-domain (FDTD) simulation indicated that the electric field around the UL-AuNPs increased due to the presence of nanothorns.

Investigation of localized surface plasmon/grating-coupled surface plasmon enhanced photocurrent in TiO2 thin films.

We fabricated plasmonic gold nanoparticle (AuNP)-TiO2 nanocomposite films and measured the photocurrent that originates from the water-splitting reaction catalyzed by the AuNP-TiO2 nanocomposite photoelectrocatalytic (PEC) electrode. The localized surface plasmon resonance (LSPR) of the gold nanoparticles affected the generation of photocurrent by TiO2 upon illumination with visible light. Electrochemical impedance spectroscopy (EIS) revealed that the improvement in the photocurrent generation originates from an enhancement in electron-hole pair generation induced by the SPR of the plasmonic gold nanoparticles rather than the extension of the electron lifetime. Moreover, we introduced a novel method to enhance the photocurrent of TiO2 by a multiple plasmonic effect, i.e., LSPR of plasmonic gold nanoparticles and the grating-coupled propagating SP on a gold grating. We fabricated the AuNP-TiO2 nanocomposites on a gold-coated Blu-ray disc recordable (BD-R). The enhancement of the photocurrent due to the combination of LSPR and the grating-coupled SP was investigated.

Fabrication of fluorescence tunable electrospun conjugated polycarbazole fibers containing gold nanoparticles.

In this report, we demonstrate a novel way to tune the fluorescence property of electrospun conjugated polymer fibers. The basic strategy is to use a soluble precursor polymer with gold nanoparticles for electrospinning, which is then cross-linked by applying potential cycles in an electrochemical cell. Electroactive carbazole units in electrospun precursor polymer fibers were converted to conjugated polymer fibers. Since the conjugated polymer fibers can be formed, the fluorescence from the conjugated polymer fibers can be tuned by the rate of the conversion and doping of the fibers. Furthermore, the quenching of the fluorescence, which overlaps with the plasmon band of the gold nanoparticles, was observed. The quenching of the fluorescence properties of the fibers was dependent on the amount of gold nanoparticles inside the fibers.

Detection of adrenaline on poly(3-aminobenzylamine) ultrathin film by electrochemical-surface plasmon resonance spectroscopy.

In this Article, we present a novel method to detect adrenaline on poly(3-aminobenzylamine) (PABA) ultrathin films by electrochemical-surface plasmon resonance (EC-SPR) spectroscopy. We prepared a PABA film, which specifically reacts with adrenaline, on a gold electrode by electropolymerization of 3-aminobenzylamine. The specific reaction of benzylamine within the PABA structure with adrenaline was studied by XPS, UV-vis spectroscopy, and EC-SPR techniques. Adrenaline was detected in real time by EC-SPR spectroscopy, which provides simultaneous monitoring of both optical SPR reflectivity and electrochemical current responses upon injecting adrenaline into the PABA thin film. The number of changes in both current and SPR reflectivity on the injection of adrenaline exhibited the linear relation to the concentration, and the detection limit was 100 pM. The responses were distinctive to those for uric acid and ascorbic acid, which are major interferences of adrenaline.

Transmission surface plasmon resonance techniques and their potential biosensor applications.

Transmission surface plasmon resonance (TSPR) is an unusual extraordinary optical transmission that is more transparent at certain wavelengths than expected by classical theory. The three main plasmonic structures that providing this phenomenon are nanohole arrays, diffraction gratings, and nanoslit arrays. This extraordinary optical transmission phenomenon is produced as a result of surface plasmon excitations. The shifting in TSPR responses upon changing of dielectric environment at the surface of a metallic film was observed. After TSPR was discovered from metallic nanohole arrays in 1998, the number of papers about this topic rapidly increased. In the 20 years since, TSPR has been utilized to improve the detection limits, sensitivity, selectivity, and dynamic range of biosensing devices, resulting in them having greater potential for commercialization. This review gives a broad overview of the TSPR phenomenon, the development of this technique, and the typical experimental setups used to acquire TSPR signals; it also describes how they are applied in the field of research into biosensors.

Ammonia Gas Detection under Various Humidity Conditions Using Waveguide Surface Plasmon Resonance Spectroscopy.

Analysis of NH3 gas under various humidity conditions was conducted using a waveguide surface plasmon resonance (SPR) sensor with dual sensing parts. Two pairs of Ag films/sensing polymer films were prepared separately on a waveguide core of BK-7 slide glass. Poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) were used as sensing materials. A white light was guided through the core by illuminating the substrate edge, and the SPR property was investigated by observing the output light spectrum. The thicknesses of PAA and PVA films were adjusted to induce SPR at different wavelengths. PAA exhibited remarkable response against NH3 gas, but it also exhibited a strong dependence on humidity. In contrast, PVA responded to humidity but hardly responded to NH3 gas below 20 ppm. The dual sensing would allow us to conduct precise NH3 measurements under various humidity conditions.

Grating-coupled surface plasmon resonance enhanced organic photovoltaic devices induced by Blu-ray disc recordable and Blu-ray disc grating structures.

In this work, we studied the performance enhancement of organic thin-film solar cells (OSCs) originating from the presence of diffraction gratings on the surface of the active layer. Two types of diffraction gratings, periodic gratings (Blu-ray disc recordable: BD-R) and quasi-random gratings (Blu-ray disc: BD), were employed as master templates for grating structures. The grating structures were introduced to the surfaces of poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) films, which were the active layers of the solar cells. The addition of the grating structures led to an increase of light absorption in the absorption region of P3HT:PCBM induced by light scattering. Furthermore, the grating-coupled surface plasmon resonance generated additional light absorption peaks. With illumination of non-polarized light at a normal incident angle, the short-circuit current densities of the BD-R and BD solar cells improved by 11.05% and 10.6%, respectively. Efficiency improvements of 19.28% and 3.21% were also observed for the BD-R and BD devices, respectively. Finally, the finite-difference time-domain simulation results revealed an enhanced electric field in the P3HT:PCBM layer, especially in the BD-R OSC devices.

Application of Long-Range Surface Plasmon Resonance for ABO Blood Typing.

In this study, we demonstrate a long-range surface plasmon resonance (LR-SPR) biosensor for the detection of whole cell by captured antigens A and B on the surface of red blood cells (RBCs) as a model. The LR-SPR sensor chip consists of high-refractive index glass, a Cytop film layer, and a thin gold (Au) film, which makes the evanescent field intensity and the penetration depth longer than conventional SPR. Therefore, the LR-SPR biosensor has improved capability for detecting large analytes, such as RBCs. The antibodies specific to blood group A and group B (Anti-A and Anti-B) are covalently immobilized on a grafting self-assembled monolayer (SAM)/Au surface on the biosensor. For blood typing, RBC samples can be detected by the LR-SPR biosensor through a change in the refractive index. We determined that the results of blood typing using the LR-SPR biosensor are consistent with the results obtained from the agglutination test. We obtained the lowest detection limits of 1.58 × 105 cells/ml for RBC-A and 3.83 × 105 cells/ml for RBC-B, indicating that the LR-SPR chip has a higher sensitivity than conventional SPR biosensors (3.3 × 108 cells/ml). The surface of the biosensor can be efficiently regenerated using 20 mM NaOH. In summary, as the LR-SPR technique is sensitive and has a simple experimental setup, it can easily be applied for ABO blood group typing.

In situ electrochemical-transmission surface plasmon resonance spectroscopy for poly(pyrrole-3-carboxylic acid) thin-film-based biosensor applications.

In this study, we describe the combination of transmission surface plasmon resonance (TSPR) and electrochemical techniques for the application to biosensors with conducting polymers. Electropolymerization was employed to construct poly(pyrrole-3-carboxylic acid) (PP3C) film on a gold-coated grating substrate using pyrrole-3-carboxylic acid (P3C) monomer solution in 0.5 M H(2)SO(4). In situ electrochemical-transmission surface plasmon resonance (EC-TSPR) measurements were carried out to study the kinetic and electroactivity properties of PP3C film. Immobilization of antihuman IgG on the activated surface and the binding process of human IgG and antihuman IgG in neutral solution could be detected in situ by EC-TSPR measurement. The surface modification steps on the PP3C layer led to an increase in intensity of the transmission peak. The performance, sensitivity, and utility of EC-TSPR spectroscopy showed obvious advantages for the detection of binding process with the simple experimental setup, and could be applied to the study of biomolecular interactions in various systems.

Grating-coupled surface plasmon enhanced short-circuit current in organic thin-film photovoltaic cells.

In this study, we demonstrate the fabrication of grating-coupled surface plasmon resonance (SPR) enhanced organic thin-film photovoltaic cells and their improved photocurrent properties. The cell consists of a grating substrate/silver/P3HT:PCBM/PEDOT:PSS structure. Blu-ray disk recordable substrates are used as the diffraction grating substrates on which silver films are deposited by vacuum evaporation. P3HT:PCBM films are spin-coated on silver/grating substrates. Low conductivity PEDOT:PSS/PDADMAC layer-by-layer ultrathin films deposited on P3HT:PCBM films act as the hole transport layer, whereas high conductivity PEDOT:PSS films deposited by spin-coating act as the anode. SPR excitations are observed in the fabricated cells upon irradiation with white light. Up to a 2-fold increase in the short-circuit photocurrent is observed when the surface plasmon (SP) is excited on the silver gratings as compared to that without SP excitation. The finite-difference time-domain simulation indicates that the electric field in the P3HT:PCBM layer can be increased using the grating-coupled SP technique.

Thiolene-based microfluidic flow cells for surface plasmon resonance imaging.

Thiolene-based microfluidic devices have been coupled with surface plasmon resonance imaging (SPRI) to provide an integrated platform to study interfacial interactions in both aqueous and organic solutions. In this work, we develop a photolithographic method that interfaces commercially available thiolene resin to gold and glass substrates to generate microfluidic channels with excellent adhesion that leave the underlying sensor surface free from contamination and readily available for surface modification through self-assembly. These devices can sustain high flow rates and have excellent solvent compatibility even with several organic solvents. To demonstrate the versatility of these devices, we have conducted nanomolar detection of streptavidin-biotin interactions using in situ SPRI.