Remote Biosensing with Polychromatic Optical Waveguide Using Blue Light‐Emitting Organic Nanowires Hybridized with Quantum Dots

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107498/1/adfm201304039.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/107498/2/adfm201304039-sup-0001-S1.pd

Polychromatic ZnO/CdxZn1-xO composite nanorods prepared by simple chemical methods: nanoscale optical characteristics

We report the fabrication and nanoscale optical characteristics of polychromatic ZnO/CdxZn1-xO composite nanorods prepared by simple hydrothermal and sol-gel chemical methods. Hydrothermally grown ~300 nm diameter and ~3.5 μm long ZnO nanorods were coated, using the sol-gel method, with a thin CdxZn1-xO layer having a spatially varying Cd mole fraction, where x ranged from x = 0 to 1. Full control of the emission color, including white emission, was achieved by simply varying the local Cd mole fraction along the single ZnO/CdxZn1-xO nanorod. The continuous variation of the optical band gap energy along the single nanorod was visualized using nanoscale confocal absorption spectral imaging.1111sciescopu

Optical logic operation via plasmon-exciton interconversion in 2D semiconductors

Nanophotonic devices manipulating light for high-speed computing are a counterpart of speed-limited electronic circuits. Although plasmonic circuits are a promising platform for subwavelength miniaturization, the logic-operation principle is still limited to mimicking those of photonic waveguides using phase shifts, polarization, interference, and resonance. Meanwhile, reconfigurable interconversion between exciton and plasmon engender emerging applications like exciton transistors and multiplexers, exciton amplifiers, chiral valleytronics, and nonlinear excitonics. Here, we propose optical logic principles realized by exciton-plasmon interconversion in Ag-nanowires (NW) overlapped on transition metal dichalcogenides (TMDs) monolayers. Excitons generated from TMDs couple to the Ag-NW plasmons, eventually collected as output signals at the Ag-NW end. Using two lasers, we demonstrate AND gate by modulating single excitons in Ag-NW on MoS2 and a half-adder by modulating dual excitons in lateral WSe2 and WS2. Moreover, a 4-to-2 binary encoder is realized in partially overlapped MoSe2 and MoS2 using four-terminal laser inputs. Our results represent great advances in communication processing for optical photonics integrable with subwavelength architectures. © The Author(s) 201

Spectroscopic Evidence of Energy Transfer in BODIPY-Incorporated Nano-Porphyrinic Metal-Organic Frameworks

Metal–organic frameworks (MOFs) represent a class of solid-state hybrid compounds consisting of multitopic organic struts and metal-based nodes that are interconnected by coordination bonds, and they are ideal for light harvesting due to their highly ordered structure. These structures can be constructed with chromophore organic ligands structures for the purpose of efficient light harvesting. Here, we prepared porphyrin-based nano-scaled MOFs (nPCN-222) with BODIPY and I2BODIPY photosensitizers by incorporating BODIPY/I2BODIPY into nPCN-222 (nPCN-BDP/nPCN-I2BDP) and demonstrated resonance energy transfer from the donor (BODIPY/I2BODIPY) to the acceptor (nPCN-222) resulting in greatly enhanced fluorescence of nPCN-222, as visually manifested by time-resolved and space-resolved fluorescence imaging of the nano-scaled MOFs

Enhancement of light-matter interaction and photocatalytic efficiency of Au/TiO2 hybrid nanowires

Metal/TiO2 hybrid nanostructures offer more efficient charge separation and a broader range of working wavelengths for photocatalytic reactions. The sizes and shapes of such hybrid nanostructures can affect the charge separation performance when the structures interact with light, but assessments of the interaction of light with these metal-TiO2 nanostructures have only been carried out on ensemble averages, hindering both systematic descriptions of such hybrid structures and the design of new ones. Here, we fabricated TiO2 nanotubes (NTs) with and without core Au nanowires (NWs), and used spectroscopy and calculations to assess their scattering and absorption of light at the single NW level. According to the results of spectral imaging and numerical calculations, the Au/TiO2 NWs scattered and absorbed light substantially more strongly than did the plain TiO2 NTs. Measurements of the degradation of the AO7 dye to assess the photocatalytic performance of the Au/TiO2 NWs were consistent with optical measurements demonstrating a two-fold improvement over plain TiO2 NTs under 360-nm-wavelength UV illumination. Our results suggests that nanoscale optical imaging can be used to visualize the performance of the photocatalytic reaction at the single nano-object level. © 2016 Optical Society of America1541sciescopu

Gold nanoparticle hybridized rubrene nanofibers made by electrospinning: enhancement of optical and structural properties

We prepared gold nanoparticle (Au NP) hybridized organic rubrene nanofibers (NFs) using a convenient electrospinning method. Au NPs of size 2–3 nm were incorporated throughout the light emitting rubrene NFs, which was confirmed by high resolution transmission electron microscopy. Au NP hybridized rubrene NFs showed a distinct nanoporous surface, compared to the smooth surface of rubrene NFs. Nanoscale confocal spectroscopy was performed on a single NF level and the results showed that the photoluminescence (PL) of the hybrid NFs made with 15 wt% Au NP mixture solution was 2.5 times higher than the PL of the rubrene NFs. And the optical extinction (scattering and absorption) of hybrid NFs increased monotonically with increasing Au NP concentrations. These enhanced optical properties of hybrid NFs were attributed to localized surface plasmon resonance of the embedded Au NPs. Structural modification from the monoclinic phase to the orthorhombic phase of the rubrene structure was obtained by XRD analysis indicating a better ordering along the rubrene ab plane of the hybrid NFs.1441sciescopu

Energy transfer effect of hybrid organic rubrene nanorod with CdSe/ZnS quantum dots: Application to optical waveguiding modulators

Organic rubrene (5,6,11,12-tetraphenyltetracene) nanorods (NRs) were fabricated through the physical vapor transport method for the study of active fluorescence optical waveguiding and its modulation. The functionalized CdSe/ZnS quantum dots (QDs) with blue and green emissions were partially attached to the surface of the rubrene NR. Using a high resolution laser confocal microscope (LCM), the nanoscale photoluminescence (PL) intensity of the pristine rubrene portion of the hybrid NR/QDs was observed to be considerably enhanced after it was attached with blue (or green) QDs. The nanoscale optical waveguiding characteristics of the hybrid NR/QDs were investigated in terms of the output LCM PL spectra as a function of propagation distance. We observed more efficient optical waveguiding characteristics from the hybrid rubrene NR/blue-QDs than from the pristine NR and the hybrid rubrene NR/green-QDs. These results can be analyzed in terms of the higher Förster resonance energy transfer efficiency for hybrid rubrene NR/blue-QDs system. The results and analysis were supported by a drastic decrease of exciton lifetime of QDs in the hybrid region as measured by time-resolved PL decay curves.101sciescopu

Dielectric Nanowire Hybrids for Plasmon-Enhanced LightMatter Interaction in 2D Semiconductors

Monolayer transition metal dichalcogenides (TMDs) with a direct band gap are suitable for various optoelectronic applications such as ultrathin light emitters and absorbers. However, their weak light absorption caused by the atomically thin layer hinders more versatile applications for high optical gains. Although plasmonic hybridization with metal nanostructures significantly enhances light-matter interactions, the corrosion, instability of the metal nanostructures, and the undesired effects of direct metal-semiconductor contact act as obstacles to its practical application. Herein, we propose a dielectric nanostructure for plasmon-enhanced light-matter interaction of TMDs. TiO2 nanowires (NWs), as an example, are hybridized with a MoS2 monolayer on various substrates. The structure is implemented by placing a monolayer MoS2 between a TiO2 NW for a photonic scattering effect and metallic substrates with a spacer for the plasmonic Purcell effect. Here, the thin dielectric spacer is aimed at minimizing emission quenching from direct metal contact, while maximizing optical field localization in ultrathin MoS2 near the TiO2 NW. An effective emission enhancement factor of similar to 22 is attained for MoS2 near the NW of the hybrid structure compared to the one without NWs. Our work is expected to facilitate a hybridized platform based on 2D semiconductors for high-performance and robust optoelectronics via engineering dielectric nanostructures with plasmonic materials.11Nsciescopu

Dielectric Nanowire Hybrids for Plasmon-Enhanced Light-Matter Interaction in 2D Semiconductors

Monolayer transition metal dichalcogenides (TMDs) with a direct band gap are suitable for various optoelectronic applications such as ultrathin light emitters and absorbers. However, their weak light absorption caused by the atomically thin layer hinders more versatile applications for high optical gains. Although plasmonic hybridization with metal nanostructures significantly enhances light-matter interactions, the corrosion, instability of the metal nanostructures, and the undesired effects of direct metal-semiconductor contact act as obstacles to its practical application. Herein, we propose a dielectric nanostructure for plasmon-enhanced light-matter interaction of TMDs. TiO2 nanowires (NWs), as an example, are hybridized with a MoS2 monolayer on various substrates. The structure is implemented by placing a monolayer MoS2 between a TiO2 NW for a photonic scattering effect and metallic substrates with a spacer for the plasmonic Purcell effect. Here, the thin dielectric spacer is aimed at minimizing emission quenching from direct metal contact, while maximizing optical field localization in ultrathin MoS2 near the TiO2 NW. An effective emission enhancement factor of similar to 22 is attained for MoS2 near the NW of the hybrid structure compared to the one without NWs. Our work is expected to facilitate a hybridized platform based on 2D semiconductors for high-performance and robust optoelectronics via engineering dielectric nanostructures with plasmonic materials.11Nsciescopu

Electrical modulation of excitonic transition in monolayer tungsten disulfide on periodically poled ferroelectric substrates

© 2022 Korean Physical Society. Although the spectral investigation of monolayer two-dimensional transition metal dichalcogenide (1L-TMD) has been extensively performed for identifying modulation of excitonic transition, study of excitonic transition in ferroelectric/TMD hybrid structure is essential to understand and design high speed and low loss devices based on in-plane junctions. Here, we demonstrate electrical modulation of excitonic transition by transferring 1L-tungsten disulfide (WS2) onto a ferroelectric domain surface, a periodically poled lithium niobate (PPLN). We observe that exciton (A0) and trion (A−) emissions of 1L-WS2 are spatially modulated depending on the sign of the phase domain, such that A0 and A− emission is stronger at the positive (D+) and negative (D−) domain, respectively. In addition, different trends of excitonic transition of 1L-WS2 between D+ and D− domain are demonstrated by applying a back-gate bias voltage. The spatial modulation of electrical and optical characteristics of 1L-TMDs will help to design the homo- or hetero p-n junctions based on TMDs.11Nsciescopuskc