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- 2018
- imgae sensor
- internet of things
- drone
- visible light ID
- Signal-to-Noise Ratio (SNR)
- Infinite Gain Multiple Feedback (IGMF)
- Visible Light Communications (VLC)
- LED
- Trans-Impedance Amplifier (TIA)
- Optoelectronic Information Science and Engineering
- Tohoku University
- University of Northumbria
- University of Huddersfield
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[IEEE 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Nantes (2018.9.24-2018.9.27)] 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Indoor Positioning Using OFDM-Based Visible Light Communication System
摘要： Precise indoor positioning is essential to support emerging applications of location aware mobile computing. Current positioning techniques that use signals transmitted in the Gigahertz region of radio-frequency spectrum do not provide highly accurate position estimates due to multipath propagation of signals. This paper proposes a novel positioning system which uses the entities of visible light communication (VLC) system as anchors and tags. Our technique scales with the number of tags and the VLC network provides both positioning and communication capabilities. The anchor points transmit the OFDM-based VLC signals synchronously, and we estimate the time differences of arrival between anchor points and tags using positioning reference signals embedded into the air-interface of the VLC system. Simulation results show that positioning accuracy of 10 cm or better is possible for over 95% of users if the sampling clock offset is better that 10 ppm, clock jitter is below 1 ps, and a bit resolution of at least 16 bits is available.
关键词： multipath propagation,OFDM,TDOA,visible light communication,indoor positioning
更新于2025-09-04 15:30:14
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Semiconductor Heterojunctions for Enhanced Visible Light Photocatalytic H2 Production
摘要： Semiconductor-based heterojunctions have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from a high rate of electron?hole recombination and narrow photo-response range. In this paper, we report on the study of heterojunctions made from visible light active, graphitic carbon nitride, g-C3N4), and UV light active, strontium pyroniobate, Sr2Nb2O7. Heterojunctions made from a combination of g-C3N4 and nitrogen-doped Sr2Nb2O7 obtained at different temperatures were also studied to determine the effect of N doping. The photocatalytic performance was evaluated by using photocatalytic hydrogen evolution reaction (HER)from water g under visible light irradiation. It was found that the photocatalytic activities of as prepared heterojunctions are significantly higher than that of individual components under similar conditions. Heterojunction formed from g-C3N4 and N-doped Sr2Nb2O7 at 700oC (CN/SNON-700) showed better performance than heterojunction made from g-C3N4 and Sr2Nb2O7 (CN/SNO). A plausible mechanism for the heterojunction enhanced photocatalytic activity is proposed based on, relative band positions, and photoluminescence data.
关键词： graphitic carbon nitride,visible light photocatalysis,strontium pyroniobate,Semiconductor heterojunctions,hydrogen production
更新于2025-09-04 15:30:14
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Molecular motors with high quantum efficiency and visible-light responsiveness: Meeting two challenges in one design
摘要： The development of light-driven rotary molecular motors is guided by a number of key goals regarding performance and applicability. While a variety of approaches to achieve high quantum yields for small UV-driven motors have been discovered, such as incorporating a protonated or alkylated nitrogen Schiff base, less progress has been made toward the goal to power molecular motors with nondestructive visible light, which will facilitate their future usage in radiation-sensitive environments. Here, we present non-adiabatic molecular dynamics simulations based on multiconfigurational quantum chemistry to demonstrate that Schiff-base motors can maintain high quantum yields also when their conjugated systems are sufficiently large for them to rather be driven by visible light. In particular, we show that a visible-light responsive Schiff-base motor featuring dihydropyridinium and cyclopentenylidene motifs achieves quantum yields of almost 70% for each of the two photoisomerizations that underlie its rotary motion.
关键词： Molecular devices,Quantum yield,Rotary motion,Molecular dynamics,Visible light
更新于2025-09-04 15:30:14
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Novel microreactors of polyacrylamide (PAM) CdS microgels for admirable photocatalytic H2 production under visible light
摘要： Cadmium sul?de, with its narrow band gap, can be used as a photocatalyst in the visible light region for the splitting of water, but its limited number of active sites and tendency to agglomerate are problematic for producing high yields of hydrogen. Therefore, an inverse emulsion polymerization method was used to fabricate polyacrylamide (PAM) microgels as a substrate to immobilize CdS nanoparticles (PAM-CdS). The PAM microgels not only immobilized the CdS nanoparticles, but also prevented aggregation. NeCd bonds in the PAM-CdS microgels facilitated electron transfer from the PAM to the CdS resulting in more electrons participating in the H2 production process. The electrostatic interactions between the PAM and CdS also hindered the recombination of electron-hole pairs. These PAM-CdS microgels exhibit admirable photocatalytic H2 production performance with a H2 production rate of up to 5.21 mmol h?1 g?1.
关键词： Visible-light water splitting,PAM microgels,CdS,Photocatalytic H2 production
更新于2025-09-04 15:30:14
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A photoresponsive molecularly imprinted polymer with rapid visible-light-induced photoswitching for 4-ethylphenol in red wine
摘要： The trans to cis isomerization of the azobenzene chromophore in most azobenzene-based photoresponsive molecularly imprinted polymers (MIPs) is initiated by UV irradiation. This limits the application of these materials in cases where UV light toxicity is an issue, such as in biological systems, food monitoring, and drug delivery. Herein we report a tetra-ortho-methyl substituted azobenzene, (4-[(4-methacryloyloxy)-2,6-dimethyl phenylazo]-3,5-dimethyl benzenesulfonic acid (MADPADSA). The photoswitching of MADPADSA could be induced by visible-light in 4-hydroxyethylpiperazineethanesulfonic acid (HEPES) buffer-ethanol (4:1, v/v) at pH 7.0, however, the photo-isomerization was slow. With the use of MADPADSA as a functional monomer, NaYF4:Yb3+,Er3+ as a substrate, 4-ethylphenol (4-EP) as a template, a novel photoresponsive surface molecularly imprinted polymer NaYF4:Yb3+,Er3+@MIP was obtained. The NaYF4:Yb3+,Er3+@MIP displayed rapid visible-light-induced photoswitching. The NaYF4:Yb3+,Er3+ substrate could efficiently increase the trans to cis isomerization rate of the photoresponsive MIP on its surface, which was faster than that of the corresponding azobenzene monomer MADPADSA. Possible reasons for this effect were investigated by fluorescence spectroscopy. NaYF4:Yb3+,Er3+@MIP displayed good specificity toward 4-EP with a specific binding constant (Kd) of 3.67 × 10?6 mol L?1 and an apparent maximum adsorption capacity (Qmax) of 10.73 μmol g?1, respectively. NaYF4:Yb3+,Er3+@MIP was applied to determine the concentration of 4-EP in red wine with good efficiency and a limit of detection lower than the value that could cause an unpleasant off-flavor.
关键词： Molecularly imprinted polymer,Visible-light-induced photoswitching,4-Ethylphenol,Red wine,Azobenzene
更新于2025-09-04 15:30:14
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Enhanced Visible Light Sensitization of N-doped TiO2 Nanotubes Containing Ti-Oxynitride Species Fabricated via Electrochemical Anodization of Titanium Nitride
摘要： The concentration and chemical state of nitrogen represent critical factors to control the band-gap narrowing and the enhancement of visible light harvesting in nitrogen-doped titanium dioxide. In this study, photocatalytic TiO2-N nanoporous structures were fabricated by the electrochemical anodization of titanium nitride sputtered films. Doping was straightforwardly obtained by oxidizing as-sputtered titanium nitride films containing N-metal bonds varying from 7.3 to 18.5 % in the Ti matrix. Severe morphological variations into the as-anodized substrates were registered at different nitrogen concentration and studied by Small-Angle X-ray Scattering. Titanium nitride films with minimum N content of 6.2 at% N led to a quasi-nanotubular geometry, whilst an increase in N concentration up to 23.8 at% determined an inhomogeneous, polydispersed distribution of nanotube apertures. The chemical state of nitrogen in the TiO2 matrix was investigated by X-ray Photoelectron Spectroscopy depth profile analysis and correlated to the photocatalytic performance. The presence of Ti-N and β-Ti substitutional bonds, as well as Ti-oxynitride species was revealed by the analysis of N 1s X-ray Photoelectron Spectroscopy High Resolution spectra. The minimum N content of 4.1 at% in the TiO2-N corresponded to the lowest Ti-oxynitride ratio of 13.5 %. The relative variation of N-metal bonds was correlated to the visible light sensitization and the highest Ti-N/Ti oxynitride ratio of 3.3 was attributed to the lowest band-gap of 2.7 eV and associated to a threefold increase in the degradation of organic dye. Further increase of N doping led to a dramatic drop of Ti-N/Ti oxynitride ratio, from 3.3 to 0.4, which resulted in a loss photocatalytic activity. The impact of the chemical state of nitrogen towards efficient doping of TiO2 nanotubes is demonstrated with a direct correlation to the N loading and a strategy to optimise these factors based on a simple, rapid synthesis from titanium nitride.
关键词： visible light sensitization,photocatalytic performance,titanium nitride,nitrogen-doped titanium dioxide,electrochemical anodization
更新于2025-09-04 15:30:14
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Ultrasonic Studies of Solid Azobenzene-Decorated Polymer Thin Films
摘要： This work investigates the effect of ultrasound on switching of cis azobenzene isomers to their trans counterparts in solid films of methyl methacrylate and methacryloyloxyazobenzene copolymers [P(MMA/MOAB)]. Ultraviolet?visible and 1H nuclear magnetic resonance spectroscopies demonstrate that 46% of the cis isomer converts to the trans form purely by ultrasonic agitation and 46% converts to the trans isomer by localized ultrasound-induced heating effects. Comparative studies of isomerization by ultrasound wave, heat, and visible irradiation show that ultrasound exposure requires a longer time to switch the cis-to-trans conformation. The estimated activation energy for the cis-to-trans conversion in solid polymer films is shown to be comparable to previous values of azobenzene isomerization, indicating that incorporation of the chromophore in a polymeric system affects the kinetics of transition but not the barriers to conformational change.
关键词： azobenzene,nuclear magnetic resonance spectroscopy,polymer thin films,ultrasound,isomerization,ultraviolet?visible spectroscopy
更新于2025-09-04 15:30:14
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Plasmon Tunability of Gold Nanostars at the Tip Apexes
摘要： Herein, we present an optimized bottom-up approach to fabricate homogeneous Au nanostars with plasmon resonances fully tunable between the red and the infrared. The synthetic method relies on the kinetic control of the reaction upon optimization of the reactant concentrations (i.e., gold seeds, reducing agent, and gold salt). Optical enhancing properties of the obtained materials are demonstrated by using SERS with visible and infrared lasers.
关键词： SERS,plasmon tunability,gold nanostars,visible and infrared lasers
更新于2025-09-04 15:30:14
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Manganese phosphinocarbodithioate for RAFT polymerisation with sunlight-induced chain end post-treatment
摘要： A new manganese RAFT agent of the formula Cp(CO)2MnP(Ph)2C(vS)SCH(CH3)Ph was synthesized in a good overall yield by a three-step reaction from cymantrene and diphenylphosphine as the main starting materials. This complex proved to be e?cient for the control of RAFT polymerisation of St, n-BA and DMAAm. The reaction course could be conveniently monitored by 31P NMR spectroscopy. The controlled character of these polymerisations and the integrity of the polymer chain ends were demonstrated by the synthesis of diblock copolymers of St and n-BA. In the case of long polymerisation times (i.e. for PSt), photo-induced polymer chain coupling reactions were detected. Importantly, removal of the Mn-RAFT-ω-chain end by visible light irradiation led to the formation of a monomodal SH-terminated PSt. These phenomena were evidenced by IR spectroscopy, SEC with RI and UV detection modes and by ESI mass spectrometry.
关键词： sunlight-induced chain end post-treatment,visible light irradiation,manganese phosphinocarbodithioate,RAFT polymerisation,diblock copolymers
更新于2025-09-04 15:30:14
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Efficient Indoor Data Transmission with Full Dimming Control in Hybrid Visible Light / Infrared Communication Systems
摘要： We design a hybrid visible light (VL) and infrared (IR) data transmission scheme for indoor visible light communication (VLC) systems with multi-pulse position modulation (MPPM) dimming control. A low-power IR light-emitting diode (LED) is adopted to assist the VL downlink especially when the dimming level of VL is low. Both VL and IR orthogonal frequency division multiplexing (OFDM) signals are transmitted alternately during the “on” and “off” periods of MPPM dimming controlled pulses. In this way, MPPM “off” periods can be efficiently utilized to convey data information without affecting illumination level. This arrangement ensures reliable data transmission under all illumination conditions including dark scenario. Numerical results show that the additional IR link can always facilitate the use of low M-ary quadrature amplitude modulation (M-QAM) levels. The fluctuation of required M-QAM symbol rates caused by dimming control can also be mitigated. At low dimming levels, both the receiver sensitivity requirement for the VL link and the total required transmit power can be significantly alleviated while maintaining a constant data rate at BER < 10-3. Even with limited launching power, the proposed scheme can still extend dimming control range while achieving stable and reliable transmission quality effectively.
关键词： multi-pulse position modulation (MPPM),Visible light communication (VLC),infrared (IR) communication,dimming control,orthogonal frequency division multiplexing (OFDM),hybrid transmission
更新于2025-09-04 15:30:14