Significantly Boosted Photothermoelectric Effect via Carrier Injection in Au Decorated SWCNT Films for Infrared Detection

Carbon nanotubes (CNTs) have established their promising application as infrared photodetector and the photothermoelectric (PTE) effect is demonstrated to play a critical role. While extensive studies are focused on the optoelectronic behaviors, the thermoelectric conversion involved in the PTE has been pursued to less extent probably due to the overall low thermopower under infrared (IR) illumination. Herein, to trigger a stronger PTE response, Au/CNT heterojunctions are formed by Au nanoparticles (NPs) decoration of CNT films to facilitate both light absorption and carrier transportation, so that thermoelectric property is enhanced simultaneously. Significant boost on infrared radiation energy conversion capability is therefore enabled in Au NPs decorated CNT film, delivering maximum output voltage of 26.1 mV and power of 27.3 µW, outperforming the state-of-the art photodetectors based on PTE effect. The transport mechanism is revealed via combining in situ Kelvin Probe Force Microscope mapping of the surface potential and macroscopic transport and output performances under IR illumination. Finally, the IR detection function is validated via an 8-channel IR detector prototype, presenting sensitive responsivity and long-term cyclic stability. The study thus demonstrates the PTE effect as a promising platform toward high-performance optoelectronic applications such as IR detection and solar energy harvesting.     

A plasmonically enhanced polymer solar cell with gold–silica core–shell nanorods

We report the use of chemically synthesized gold (Au)–silica core–shell nanorods with the length of 92.5 ± 8.0 nm and diameter of 34.3 ± 4.0 nm for the efficiency enhancement of bulk heterojunction (BHJ) polymer solar cells. Silica coated Au nanorods were randomly blended into the BHJ layers of these solar cells. This architecture inhibits the carrier recombination at the metal/polymer interface and effectively exploits light absorption at the surface plasmon resonance wavelengths of the Au–silica nanorods. To match the two plasmon resonant peaks of the Au–silica nanorods, we employed a low bandgap polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′] dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) to construct a solar cell. The absorption spectrum of PCPDTBT:[6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₀BM) is relatively wide and matches the two plasmon resonance peaks of Au–silica nanorods, which leads to greater plasmonic effects. We also constructed the poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PC₆₀BM) cells for comparison. The absorption spectrum of P3HT:PC₆₀BM only overlaps one of the plasmon resonance peak of Au–silica nanorods. The efficiency of the P3HT:PC₆₀BM device incorporating optimized Au–silica nanorods is enhanced by 12.9% from 3.17% to 3.58%, which is due to the enhanced light absorption. Compared with the P3HT:PC₆₀BM device with Au–silica nanorods, the PCPDTBT:PC₇₀BM device with 1 wt% Au–silica nanorods concentration has a higher efficiency of 4.4% with an increase of 26%.     

Photothermal Killing of Cancer Cells by the Controlled Plasmonic Coupling of Silica‐Coated Au/Fe2O3 Nanoaggregates

Tumor ablation by thermal energy via the irradiation of plasmonic nanoparticles is a relatively new oncology treatment. Hybrid plasmonic‐superparamagnetic nanoaggregates (50–100 nm in diameter) consisting of SiO₂‐coated Fe₂O₃ and Au (≈30 nm) nanoparticles were fabricated using scalable flame aerosol technology. By finely tuning the Au interparticle distance using the SiO₂ film thickness (or content), the plasmonic coupling of Au nanoparticles can be finely controlled bringing their optical absorption to the near‐IR that is most important for human tissue transmittance. The SiO₂ shell facilitates also dispersion and prevents the reshaping or coalescence of Au particles during laser irradiation, thereby allowing their use in multiple treatments. These nanoaggregates have magnetic resonance imaging (MRI) capability as shown by measuring their r2 relaxivity while their effectiveness as photothermal agents is demonstrated by killing human breast cancer cells with a short, four minute near‐IR laser irradiation (785 nm) at low flux (4.9 W cm^‐2).     

Chiral AuCuAu Heterogeneous Nanorods with Tailored Optical Activity

Here, a facile wet‐chemistry route for the selective growth of crystalline copper (Cu) along the sides of gold nanorods (Au NRs) in the presence of a hexadecylamine (HDA) is reported. The resulting heterostructures feature part etching of copper by galvanic replacement reaction and form crystalline AuCu alloy metal on one side of the Au NRs. By virtue of the dipeptide (cysteine‐phenylalanine, Cys‐Phe) ligand used during synthesis, the AuCuAu heteronanorods (HNRs) exhibit strong circular dichroism (CD) in the wavelength range of 400–1000 nm. The plasmonic chirality can be tailored by increasing the length of the Au NRs, the scale of Cu nanocrystals on the Au NRs, and the amount of gold chloride for postgrowth, resulting in an anisotropy factor (g factor) as high as 0.57 × 10^?2. The strong CD signals are attributed to the local electromagnetic field. Under circular polarized light (CPL) illumination, the chiral plasmonic AuCuAu nanostructure exhibits high efficiency for light polarization dependent reactive oxygen species (¹O₂) that is 22.31 times that of Au NRs. The results of this study demonstrate that the chiral enantiomer provides a chirality dependent avenue for highly efficient phototherapy.     

The Interplay between Surface Plasmon Resonance and Switching Properties in Gold@Spin Crossover Nanocomposites

Rod‐like gold nanoparticles are directly embedded in a 1D‐polymeric spin crossover (SCO) material leading to singular Au@SCO nanohybrid architectures. The resulting architectures are designed to promote a synergetic effect between ultrafast spin‐state photoswitching and photothermal properties of plasmonic nanoparticles. This synergy is evidenced by the strong modulation of the surface plasmon resonance of the gold nanorods through the spin‐state switching of the SCO component and also the strong enhancement of the photoswitching efficiency compared to pure SCO particles. This remarkable synergy results from the large modulation of the dielectric properties of the SCO polymer upon its thermal switching and the enhancement of the heating of these hybrid nanostructures upon excitation of the surface plasmon resonance of the gold nanorods.     

Bottom‐Up Tailoring of Plasmonic Nanopeapods Making Use of the Periodical Topography of Carbon Nanocoil Templates

Au nanoparticle chains embedded in helical Al₂O₃ nanotubes (“nanopeapods”) are synthesized by annealing carbon nanocoils coated with Au by sputtering and Al₂O₃ by atomic layer deposition. Regular spacing between nanoparticles with a sharp size distribution is achieved by fragmentation of the Au coating in agreement with the pitch of the nanocoils arising from three‐dimensional periodical topography of the carbon nanocoil templates. A strong plasmonic resonance behavior of the fabricated nanopeapods manifests itself in confocal laser scanning microscopy by a clear polarization contrast at red wavelengths, which is absent in the blue. Numerical simulations confirm an incisive resonance enhancement for longitudinal polarization and suggest the nanopeapods as promising candidates for highly efficient, ultrathin waveguides. The waveguiding properties of the nanopeapods are investigated by electron energy‐loss spectroscopy and energy‐filtered TEM imaging.     

Plasmonic Nanowire‐Enhanced Upconversion Luminescence for Anticounterfeit Devices

A novel, efficient, cost‐effective, and high‐level security performance anticounterfeit device achieved by plasmonic‐enhanced upconversion luminescence (UCL) is demonstrated. The plasmonic architecture consists of the randomly dispersed Ag nanowires (AgNWs) network, upconversion nanoparticles (UCNPs) monolayer, and metal film, in which the UCL is enhanced by a few tens, compared to reference sample, becuase the plasmonic modes lead to the concentration of the incident near infrared (NIR) light in the UCNPs monolayer. In the configuration, both the localized surface plasmons (LSPs) around the metallic nanostructures and gap plasmon polaritons (GPPs) confined in the UCNPs monolayer, significantly contribute to the UCL enhancement. The UCL enhancement mechanism resulting from enhanced NIR absorption, boosted internal quantum process, and formation of strong plasmonic hot spots in the plasmonic architecture is analyzed theoretically and numerically. More interestingly, a proof‐of‐concept anticounterfeit device using the plasmonic‐enhanced UCL is proposed, through which a nonreusable and high‐level cost‐effective security device protecting the genuine products is realized.     

Efficiency Enhancement of Organic Solar Cells by Using Shape‐Dependent Broadband Plasmonic Absorption in Metallic Nanoparticles

It is been widely reported that plasmonic effects in metallic nanomaterials can enhance light trapping in organix solar cells (OSCs). However, typical nanoparticles (NP) of high quality (i.e., mono‐dispersive) only possess a single resonant absorption peak, which inevitably limits the power conversion efficiency (PCE) enhancement to a narrow spectral range. Broadband plasmonic absorption is obviously highly desirable. In this paper, a combination of Ag nanomaterials of different shapes, including nanoparticles and nanoprisms, is proposed for this purpose. The nanomaterials are synthesized using a simple wet chemical method. Theoretical and experimental studies show that the origin of the observed PCE enhancement is the simultaneous excitation of many plasmonic low‐ and high‐order resonances modes, which are material‐, shape‐, size‐, and polarization‐dependent. Particularly for the Ag nanoprisms studied here, the high‐order resonances result in higher contribution than low‐order resonances to the absorption enhancement of OSCs through an improved overlap with the active material absorption spectrum. With the incorporation of the mixed nanomaterials into the active layer, a wide‐band absorption improvement is demonstrated and the short‐circuit photocurrent density (J_sc) improves by 17.91%. Finally, PCE is enhanced by 19.44% as compared to pre‐optimized control OSCs. These results suggest a new approach to achieve higher overall enhancement through improving broadband absorption.     

Enhanced Light‐Harvesting by Integrating Synergetic Microcavity and Plasmonic Effects for High‐Performance ITO‐Free Flexible Polymer Solar Cells

In this work, a high‐performance ITO‐free flexible polymer solar cell (PSC) is successfully described by integrating the plasmonic effect into the ITO‐free microcavity architecture. By carefully controlling the sizes of embedded Ag nanoprisms and their doping positons in the stratified device, a significant enhancement in power conversion efficiency (PCE) is shown from 8.5% (reference microcavity architecture) to 9.4% on flexible substrates. The well‐manipulated plasmonic resonances introduced by the embedded Ag nanoprisms with different LSPR peaks allow the complementary light‐harvesting with microcavity resonance in the regions of 400–500 nm and 600–700 nm, resulting in the substantially increased photocurrent. This result not only signifies that the spectral matching between the LSPR peaks of Ag nanoprisms and the relatively low absorption response of photoactive layer in the microcavity architecture is an effective strategy to enhance light‐harvesting across its absorption region, but also demonstrates the promise of tailoring two different resonance bands in a synergistic manner at desired wavelength region to enhance the efficiency of PSCs.     

Optimized Design of Plasmonic MSM Photodetector

We present an optimized design for a plasmonic metal-semiconductor-metal photodetector with interdigitated electrodes with subwavelength dimensions and a single GaInNAs quantum well (QW) as an absorbing layer. The excitation of surface plasmons at the metal-semiconductor interface leads to a strong field enhancement near the metallic electrodes. This results in an increased absorption in the QW, allowing both fast electrical response of the photodetector and high quantum efficiencies. With a grating periodicity of 820 nm and electrode finger width of 460 nm a 16-fold increase in the absorption of p-polarized light in the QW is achieved in comparison to the case without electrodes.     

激光选择聚焦的响应增强型光电探测器

介绍了一种利用激光选择聚焦的结构来增强光电探测器的光电响应的方法。通过采用工作在传输模式的振幅型菲涅耳波带片,获得了较高的激光收集效率,同时也较好地抑制了背景光。当激光入射时,集成了菲涅耳波带片的InGaAs/InP p-i-n 光电探测器和InGaAs/InP 雪崩光电二极管的响应分别增强了36 倍和4 倍,而当模拟自然光的卤钨灯照射时,集成了菲涅耳波带片的两类光电探测器的响应均被抑制了30%。集成了菲涅耳波带片的探测器显现出对激光信号的较强吸收,对模拟自然光的卤钨灯光源的明显抑制。     

Vertical 3D Printed Forest-Inspired Hierarchical Plasmonic Superstructure for Photocatalysis

Efficient light-harvesting is of significant importance to achieve high solar energy utilization efficiency for various solar-driven technologies. Compared with a 2D planar structure, a 3D plasmonic structure can largely increase the light adsorption/interaction areas and also utilizes the plasmonic effect to achieve much higher light utilization efficiency. However, this remains challenging in terms of structural design, reliable manufacturing, and ability to scale up. Herein, inspired by the light absorption strategy of natural forests, a hierarchical plasmonic superstructure is demonstrated composed of vertical TiO₂ pillar arrays (as tree trunks), dense nanorod arrays (as branches), and a large number of plasmonic Au nanoparticles (as leaves). Such a forest-like plasmonic superstructure can effectively absorb light from the surface plasmonic resonance effects of Au nanoparticles and the multiple scattering of light in the hierarchical branched structure. The strong light absorption and abundant photocatalytic active sites help yield a 15-fold higher nitrogen photo-fixation activity than that of the flat TiO₂ films decorated with Au nanoparticles. The study provides an effective strategy to construct 3D plasmonic superstructures with excellent light-harvesting efficiency and high stability and can be readily applied to a range of light-driven applications     

Localized Surface Plasmon Resonance Enhanced Photocatalytic Hydrogen Evolution via Pt@Au NRs/C3N4 Nanotubes under Visible‐Light Irradiation

Au nanorods (NRs) decorated carbon nitride nanotubes (Au NRs/CNNTs) photocatalysts have been designed and prepared by impregnation–annealing approach. Localized surface plasmon resonance (LSPR) peaks of Au NRs can be adjusted by changing the aspect ratios, and the light absorption range of Au NRs/CNNTs is extended to longer wavelength even near‐infrared light. Optimal composition of Pt@Au NR₇₆₉/CNNT₆₅₀ has been achieved by adjusting the LSPR peaks of Au NRs and further depositing Pt nanoparticles (NPs), and the photocatalytic H₂ evolution rate is 207.0 µmol h^?1 (20 mg catalyst). Preliminary LSPR enhancement photocatalytic mechanism is suggested. On one hand, LSPR of Au NRs is beneficial for visible‐light utilization. On the other hand, Pt NPs and Au NRs have a synergetic enhancement effect on photocatalytic H₂ evolution of CNNTs, in which the local electromagnetic field can improve the photogenerated carrier separation and direct electron transfer increases the hot electron concentration while Au NRs as the electron channel can well restrain charge recombination, finally Pt as co‐catalyst can boost H⁺ reduction rate. This work provides a new way to develop efficient photocatalysts for splitting water, which can simultaneously extend light absorption range and facilitate carrier generation, transportation and reduce carrier recombination.     

Controlled Growth of Hierarchical Bi2Se3/CdSe-Au Nanorods with Optimized Photothermal Conversion and Demonstrations in Photothermal Therapy

Integrating multiple mechanisms to maximize photothermal conversion efficiency is a significant strategy but remains challenging to construct therapeutic agents toward photothermal tumor treatment. Here, an approach to synthesize asymmetric Bi₂Se₃/CdSe-Au hierarchical nanorods with excellent photothermal conversion is reported. Ag wetting-layer is firstly grown to help overcome the interfacial lattice mismatch and promote the site-selective growth of AgCdSe onto one end or side surface of Au nanorods. Subsequently, extraction of Ag⁺ ions out of lattice is observed during cation exchange reaction and epitaxial growth of Bi₂Se₃ shell. Bi₂Se₃/CdSe heterojunction with type-II band alignment is formed and located at the plasmonic hotspots of Au nanorods, which experiences enhanced light absorption and accelerates the charge separation of photo-excited carriers. Under excitation of near-infrared 808 nm laser, the matchstick-like Bi₂Se₃/CdSe-Au nanorods show an excellent photothermal conversion, with 4.3 times temperature increment ( Δ T) than that of bare Au nanorods. Moreover, in vitro and in vivo experiments verify them as excellent photothermal therapeutic agents.     

Multifunctional Lateral Transition‐Metal Disulfides Heterojunctions

The intrinsic spin‐dependent transport properties of two types of lateral VS₂|MoS₂ heterojunctions are systematically investigated using first‐principles calculations, and their various nanodevices with novel properties are designed. The lateral VS₂|MoS₂ heterojunction diodes show a perfect rectifying effect and are promising for the applications of Schottky diodes. A large spin‐polarization ratio is observed for the A‐type device and pure spin‐mediated current is then realized. The gate voltage significantly tunes the current and rectification ratio of their field‐effect transistors. In addition, they all demonstrate a sensitive photoresponse to blue light, and could be used as photodetector and photovoltaic device. Moreover, they generate an effective thermally driven current when a temperature gratitude appears between the two terminals, suggesting them as potential thermoelectric materials. Hence, the lateral VS₂|MoS₂ heterojunctions show a multifunctional nature and have various potential applications in spintronics, optoelectronics, and spin caloritronics.     

Plasmonic Au nanoparticles for enhanced broadband light absorption in inverted organic photovoltaic devices by plasma assisted physical vapour deposition

We use a low vacuum plasma assisted physical vapour deposition (PAPVD) method to deposit a Au nanoparticles (NPs) thin film onto the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer in inverted poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methylester (P3HT:PCBM) organic photovoltaic (OPV) devices. The Au NPs that incorporated into the PEDOT:PSS layer and reached to the active P3HT:PCBM layer can provide significant plasmonic broadband light absorption enhancement to the active layer. An approximately 50–90% improvement in short-circuit current density and in power convention efficiency has been achieved compared with those OPV devices without the plasmonic light absorption enhancement. This technique can be adopted and easily fit into most OPV device fabrication processes without changing other layers’ processing methods, morphologies, and properties.     

Highly Aligned Plasmonic Gold Nanorods in a DNA Matrix

Since the Lycurgus Cup was made in the 4th century, metal nanoparticles have attracted much interest due to the characteristics of the plasmonic and metamaterials that show beautiful colors. Despite these fascinating properties, the practical use is limited because it is difficult to control the orientation of the plasmonic nanoparticles. Here, highly aligned plasmonic gold nanorods are obtained using self‐assembled DNA material. Simple mechanical shearing results in long‐range DNA–gold nanorod arrays which show parallel, perpendicular, and zigzag configurations due to the competition between the shear force and DNA elasticity. The resulting surface plasmonic resonance properties of the aligned DNA–gold nanorods film show highly polarization‐dependent behavior in a large area, which is critical for optical and photonic applications. This simple way to form anisotropic plasmonic films can be used for plasmonic nanoparticles in potential applications such as displays and sensors.     

Plasmonic Au/TiO2‐Dumbbell‐On‐Film Nanocavities for High‐Efficiency Hot‐Carrier Generation and Extraction

Plasmon‐induced hot carriers have vast potential for light‐triggered high‐efficiency carrier generation and extraction, which can overcome the optical band gap limit of conventional semiconductor‐based optoelectronic devices. Here, it is demonstrated that Au/TiO₂ dumbbell nanostructures assembled on a thin Au film serve as an efficient optical absorber and a hot‐carrier generator in the visible region. Upon excitation of localized surface plasmons in such coupled particle‐on‐film nanocavities, the energetic conduction electrons in Au can be injected over the Au/TiO₂ Schottky barrier and migrated to TiO₂, participating in the chemical reaction occurring at the TiO₂ surface. Compared with the same dumbbell nanostructures on an indium tin oxide (ITO) film, such nanocavities exhibit remarkable enhancement in both photocurrent amplitude and reaction rate that arise from increased light absorption and near‐field amplification in the presence of the Au film. The incident‐wavelength‐dependent photocurrent and reaction rate measurements jointly reveal that Au‐film‐mediated near‐field localization facilitates more efficient electron–hole separation and transport in the dumbbells and also promotes strong d‐band optical transitions in the Au film for generation of extra hot electrons. Such nanocavities provide a new plasmonic platform for effective photoexcitation and extraction of hot carriers and also better understanding of their fundamental science and technological implications in solar energy harvesting.     

金纳米粒子-黑磷异质结的光学性能研究

为了改善黑磷(BP)光探测器因BP的弱光吸收导致的光电流小和在空气中不稳定的问题,采用加热蒸发金纳米粒子(Au NP)水溶液的方法将Au NP集合到BP光探测器的表面,增强整个结构对光的吸收率和稳定性,并通过改变Au NP水溶液的加热温度控制Au NP的密度分布。结果表明,当Au NP的密度分布达到4.5×109 cm^-2时,Au NP-BP光探测器的光电流从1.02μA(BP光探测器)增加到13.36μA(电压=1 V),光响应度也相应地增加了12倍。同时,Au NP-BP光探测器的电流值在空气中保持数天无明显变化且暗电流较低。Au NP能够有效地提升光探测器的性能,有助于光探测器的实际应用。     

Synthesis of Au–CdS Core–Shell Hetero‐Nanorods with Efficient Exciton–Plasmon Interactions

The synthesis of large lattice mismatch metal‐semiconductor core–shell hetero‐nanostructures remains challenging, and thus the corresponding optical properties are seldom discussed. Here, we report the gold‐nanorod‐seeded growth of Au–CdS core–shell hetero‐nanorods by employing Ag₂S as an interim layer that favors CdS shell formation through a cation‐exchange process, and the subsequent CdS growth, which can form complete core–shell structures with controllable shell thickness. Exciton–plasmon interactions observed in the Au–CdS nanorods induce shell thickness‐tailored and red‐shifted longitudinal surface plasmon resonance and quenched CdS luminescence under ultraviolet light excitation. Furthermore, the Au–CdS nanorods demonstrate an enhanced and plasmon‐governed two‐photon luminescence under near‐infrared pulsed laser excitation. The approach has potential for the preparation of other metal‐semiconductor hetero‐nanomaterials with complete core–shell structures, and these Au–CdS nanorods may open up intriguing new possibilities at the interface of optics and electronics.