Stable,Cost-Effective TiN-Based Plasmonic Nanocomposites with over 99% Solar Steam Generation Efficiency

Plasmonic nanoparticles (NPs), such as Au, Ag, and Cu, are considered as promising photothermal materials and attract extensive attention for freshwater production by solar steam generation. However, high cost, narrow absorption range and/or poor stability greatly limit their practical applications. Herein, a high-efficiency solar energy conversion material consisting of low-cost non-metal, extremely thermally-stable plasmonic TiN NPs and hydrophilic semi-reduced graphene oxide (semi-rGO), with broadband solar absorption capability, by a fast in situ microwave reduction method is prepared. The 2D semi-rGO serves as a support for the loading of plasmonic NPs, and meanwhile accelerates the transport and evaporation of water due to its hydrophilicity. Then, decoration of plasmonic TiN NPs further enhances the solar photon absorption and hydrophilicity while suppressing the heat loss, thanks to the layered structure of TiN/semi-rGO, improving overall solar energy utilization. Owing to the enhanced absorption and unique layered nanostructure with strong interfacial interaction, the optimal sample of TiN/semi-rGO-25% absorber achieves a high and stable water evaporation rate of ≈1.76 kg m⁻² h⁻¹ with an energy efficiency as high as 99.1% under 1 sun illumination. Furthermore, this plasmonic TiN/semi-rGO absorber is capable of producing high-quality freshwater from sustainable seawater desalination and wastewater purification processes.     

Broad-band plasmonic Cu-Au bimetallic nanoparticles for organic bulk heterojunction solar cells

In this work, a facile preparation of Cu-Au bimetallic nanoparticles (NPs) with core-shell nanostructures is reported. Importantly, as-prepared Cu-Au NPs are highly stable, solution-processable and exhibit a broad localized surface plasmon resonance (LSPR) band at long wavelengths of 550–850 nm. Highly efficient plasmonic organic solar cells (OSCs) were fabricated by embedding Cu-Au NPs in an anodic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer. The average power conversion efficiency (PCE) was enhanced from 3.21% to 3.63% for poly(3-hexylthiophene) (P3HT):phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) based devices, from 6.51% to 7.13% for poly[(ethylhexyl-thiophenyl)-benzodithiophene -(ethylhexyl)-thienothiophene](PTB7-th):PC₆₁BM based devices and from 7.53% to 8.48% for PTB7-th:PC₇₁BM based devices, corresponding to 9.5–13.4% PCE improvement. Such an improvement is very comparable to that (12.5%) obtained in those with plasmonic Au NPs but achieved at lower cost. This study thus demonstrates a novel and cost-effective approach to enhance the photovoltaic performance of OSCs, in combination with the broad-band plasmonic Cu-Au bimetallic nanostructures.     

Au/TiO2复合纳米结构增强热电子光电探测器宽谱响应性能

宽谱响应光电探测器在图像传感和光通信等领域应用前景广阔。金属微纳结构通过激发表面等离激元共振效应可高效产生热载流子,将它们与宽带隙半导体构成异质结构,便可利用热载流子开发出低成本宽谱响应光电探测器。研究设计了一种基于Au/TiO₂复合纳米结构的热电子光电探测器。其中TiO₂层经退火后形成尺度约为百纳米的凹凸结构,Au纳米颗粒层与用作电极的保形Au膜共同组成了激发表面等离激元共振的纳米结构。由于Au/TiO₂复合纳米结构的协同作用,该器件在400～900 nm范围内具有宽谱光吸收性能,器件的平均光吸收效率为33.84%。在此基础上,该器件能够探测TiO₂本征吸收波段以外的入射光子。例如,在600 nm波长处,器件的响应率为9.67μA/W,线性动态范围为60 dB,器件的上升/下降响应速度分别为1.6 ms和1.5 ms。此外,利用有限元法进行了仿真计算,通过电场分布图验证了Au/TiO₂复合纳米结构中所激发的丰富表面等离激元共振效应是其实现宽谱高效探测的原因所在。     

Detection of Glioma‐Derived Exosomes with the Biotinylated Antibody‐Functionalized Titanium Nitride Plasmonic Biosensor

Titanium nitride (TiN), as an excellent alternative plasmonic supporting material compared to gold and silver, exhibits tunable plasmonic properties in the visible and near‐infrared spectra. However, label‐free surface plasmon resonance biosensing with TiN is seldom reported due to lack of proper surface functionalization protocols. Herein, this study reports biotinylated antibody‐functionalized TiN (BAF‐TiN) for high‐performance label‐free biosensing applications. The BAF‐TiN biosensor can quantitatively detect exosomes of 30–200 nm extracellular vesicles, isolated from a human glioma cell line. The limit of detection for an exosomal membrane protein with the BAF‐TiN biosensor is found to be 4.29 × 10^?3µg mL^?1 for CD63, an exosome marker, and 2.75 × 10^?3µg mL^?1 for epidermal growth factor receptor variant‐III, a glioma specific mutant protein, respectively. In conclusion, combining the biocompatibility, high stability, and excellent label‐free sensing performance of TiN, the BAF‐TiN biosensor could have great potential for the detection of cancer biomarkers, including exosomal surface proteins.     

Titanium Nitride Modified Photoluminescence from Single Semiconductor Nanoplatelets

Titanium nitride (TiN) is an alternative plasmonic material that has the potential for visible and near‐infrared optical applications due to its distinct properties. Here, coupling effects between TiN nanohole array films and nearby excitonic emitters, semiconductor nanoplatelets (NPLs), are investigated using single particle spectroscopy. At the emission wavelength of the NPLs, the local field enhancement close to the surface of the TiN nanohole array films induces an increase in the radiative decay rates of the emitters by a factor of up to 2. This effect diminishes quickly as the distance between the TiN nanohole array films and emitters increases. At short wavelengths where the NPLs are excited, the TiN nanohole array films exhibit lossy dielectric characteristics. Local field modification at these wavelengths leads to a reduced local density of electromagnetic states, and hence the photoluminescence intensity of the emitters. This study shows the potential of TiN as an alternative plasmonic material for optoelectronic and photonic applications, especially in the long wavelength ranges.     

Recent advancements in surface plasmon polaritons-plasmonics in subwavelength structures in microwave and terahertz regimes

This paper presents a review of recent investigational studies on exciting Surface Plasmon Polaritons (SPPs) in MicroWave (MW) and TeraHertZ (THz) regimes by using subwavelength corrugated patterns on conductive or metal surfaces. This article also describes SPP Microstrip (MS) structures at microwave and terahertz frequencies, and compares their significance with that of conventional MS Transmission Lines (TL), in order to tackle the key challenges of high gain, bandwidth size, compactness, TL losses, and signal integrity in high-end electronic devices. Because they have subwavelength properties, surface plasmon polaritons are gaining attention for their improved performance and ability for miniaturization in high-speed dense circuits. They possess comparably minuscule wavelength compared to incident light (photons). Consequently, they can demonstrate stronger spatial confinement and higher local field intensity at optical frequencies. In addition to engineering spoof SPP waveguides, which are created by engraving grooves and slits on metal surfaces to allow operation on at low frequencies (microwave and terahertz), semiconductors with smaller permittivity values and thus lower free charge carrier concentration have been demonstrated as a potential candidate in plasmonic devices. If necessary, further tuning of semiconductor-based SPP structures is aided by controlling the charge carrier concentration through doping, or by external stimuli such as optical illumination or thermal excitation of charge carriers from valence to conduction bands. This article conclusively covers previously elucidated perspectives on manipulating SSPPs in the MW and THz ranges, and emphasizes how these could steer next-generation plasmonic devices.     

Impact of the Metal Adhesion Layer on the Radiation Power of Plasmonic Photoconductive Terahertz Sources

The use of plasmonic contact electrodes in a photoconductive terahertz source offers high optical-to-terahertz conversion efficiencies. The high efficiency is because plasmonic contact electrodes concentrate a large portion of the incident optical pump beam in close proximity to the contact electrodes. By reducing the average transport path length of the photo-generated carriers from the contact electrodes, a larger number of the photocarriers drift to the terahertz radiating elements of the photoconductive source within a sub-picosecond time scale. Therefore, higher terahertz radiation power levels are achieved compared to a similar photoconductive source without plasmonic contact electrodes. Au is a preferred metal for plasmonic contact electrodes because of the strong plasmonic enhancement factors it offers at near-infrared optical wavelengths. However, it requires an adhesion layer to stick well to most III–V semiconductor substrates used in photoconductive terahertz sources. In this paper, we analyze the impact of the Au adhesion layer on the performance of plasmonic photoconductive sources fabricated on a GaAs substrate. Our analysis suggests that Cr is the most promising adhesion layer for plasmonic contact electrodes. We show that the use of a Cr adhesion layer instead of Ti, which is used in previously demonstrated plasmonic photoconductive sources, offers up to an 80% enhancement in the generated terahertz powers. We report record-high terahertz power emissions of up to 6.7 mW from plasmonic photoconductive sources with Cr/Au contacts.     

Plasmonic Nanoparticles with Supramolecular Recognition

Even after more than two decades of intense studies, the research on self‐assembly processes involving supramolecular interactions between nanoparticles (NPs) is continuously expanding. Plasmonic NPs have attracted particular attention due to strong optical, electrical, biological, and catalytic effects they are accompanied with. Surface plasmon resonance characteristics of plasmonic NPs and their assemblies enable fine‐tuning of these effects with unprecedented dynamic range. In turn, the uniquely high polarizability of plasmonic nanostructures and related optical effects exemplified by surface‐enhanced Raman scattering and red–blue color changes give rise to their application to biosensing. Since supramolecular interactions are ubiquitous in nature, scientists have found a spectrum of biomimetic properties of individual and assembled NPs that can be regulated by the layer of surface ligands coating all NPs. This paradigm has given rise to multiple studies from the design of molecular containers and enzyme‐like catalysts to chiroplasmonic assemblies. Computational and theoretical advances in plasmonic effects for geometrically complex structures have made possible the nanoscale engineering of NPs, assemblies, and supramolecular complexes with biomolecules. It is anticipated that further studies in this area will be expanded toward chiral catalysis, environmental monitoring, disease diagnosis, and therapy.     

Efficient Terahertz Plasmonic Absorbers with V-Grooves Using Highly Doped Silicon Substrate and Simple Wet-Etching Techniques

We experimentally demonstrate that at terahertz frequencies perfect plasmonic absorbers made from a 3D V-groove array in a highly doped silicon wafer can be easily realized using simple wet-etching process. The surface plasmon modes can be excited by the V-groove array and get decayed when they propagate along the silicon surface and enter the grooves, inducing a broadband near-zero dip in the reflection spectra. The reflection spectrum of the fabricated absorber is characterized using a terahertz time-domain spectroscopy system, and the experimental results are in good agreement with numerical simulations. The high performance including high absorptivity and large bandwidth together with the easy fabrication processes presented in this paper make this plasmonic absorber promising for a wide range of practical applications in terahertz regime.     

Plasmonic Electrically Functionalized TiO2 for High‐Performance Organic Solar Cells

Optical effects of the plasmonic structures and the materials effects of the metal nanomaterials have recently been individually studied for enhancing performance of organic solar cells (OSCs). Here, the effects of plasmonically induced carrier generation and enhanced carrier extraction of the carrier transport layer (i.e., plasmonic‐electrical effects) in OSCs are investigated. Enhanced charge extraction in TiO₂ as a highly efficient electron transport layer by the incorporation of metal nanoparticles (NPs) is proposed and demonstrated. Efficient device performance is demonstrated by using Au NPs incorporated TiO₂ at a plasmonic wavelength (560–600 nm), which is far longer than the originally necessary UV light. By optimizing the concentration ratio of the Au NPs in the NP‐TiO₂ composite, the performances of OSCs with various polymer active layers are enhanced and efficiency of 8.74% is reached. An integrated optical and electrical model, which takes into account plasmonic‐induced hot carrier tunneling probability and extraction barrier between TiO₂ and the active layer, is introduced. The enhanced charge extraction under plasmonic illumination is attributed to the strong charge injection of plasmonically excited electrons from NPs into TiO₂. The mechanism favors trap filling in TiO₂, which can lower the effective energy barrier and facilitate carrier transport in OSCs.     

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.     

Self‐Assembly of Mechanoplasmonic Bacterial Cellulose–Metal Nanoparticle Composites

Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC–NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self‐assembly strategy is described for fabrication of complex and well‐defined BC–NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self‐assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near‐field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.     

Surface‐Activated Nanoparticles for Controlled Light‐Responsiveness

Most of the optical properties of nanoparticles (NPs) depend on a nonadditive effect, where there is a maximum (or optimum) value at a specific distance from the NP surface (proximity length). However, knowledge on the relation between the specific surface layer and light responsiveness of NPs is limited. In this study, surface properties of NPs are modulated by electron beam (e‐beam) treatment together with ionic control of the NP surface and dispersing media. The surface modification in terms of the proximity length is found to be critical to the selective enhancement of light absorbance in the ultraviolet‐visible (UV‐vis) and terahertz (THz) regions. In particular, the non‐temporarily electron‐activated NPs absorb short wavelength UV‐vis light, rendering them particulary advantageous for solar energy use. The control over the physical properties of general light‐responsive NPs is a new approach to designing solar‐energy‐based technologies.     

Enhancement of the power conversion efficiency due to the plasmonic resonant effect of Au nanoparticles in ZnO nanoripples

Au-ZnO nanoripples (NRs) were synthesized by using a sol-gel method for utilization as an electron transport layer (ETL) in inverted organic photovoltaic (OPV) cells. Absorption spectra showed that the plasmonic broadband light absorption of the ZnO NRs was increased due to the embedded Au nanoparticles (NPs). In particular, as compared to regular inverted OPV cells with a ZnO NR ETL, the incident photon-to-current efficiency of the inverted OPV cells with a Au-ZnO NR ETL was significantly enhanced due to the localized surface plasmon resonance (LSPR) effect of the Au NRs. The enhancement of the short-circuit current density (10.05 mA/cm²) of the inverted OPV cells with a Au-ZnO NR ETL was achieved by the insertion of the Au NPs into the ZnO NRs. The power conversion efficiency (PCE) of the OPV cells with Au-ZnO NRs was 3.25%. The PCE of the inverted OPV cells fabricated with a Au-ZnO NR ETL was significantly improved by 20.37% in comparison with that of inverted OPV cells fabricated with a ZnO NR ETL. This improvement can mainly be attributed to an increase in light absorption in the active layer due to the generation of the LSPR effect resulting from the existence of the Au NPs embedded in the ZnO NRs.     

太赫兹表面等离激元及其应用

金属或半导体与介质分界面上的电子与光子互作用形成的光学表面等离激元(SPP)以及人工超构材料或二维原子晶体材料表面上的电子与太赫兹波或微波互作用形成的人工表面等离激元(SSP)是小型化与集成化太赫兹有源/无源器件和太赫兹超分辨率成像的重要物理基础。随着太赫兹科学技术的发展,太赫兹表面等离激元研究在国际上受到很大关注。本文介绍了传统的光学表面等离激元及其发展,详细阐述了太赫兹波段的人工表面等离激元(SSP)和石墨烯表面等离激元(GSP)的基本原理和发展历程,对表面等离激元在太赫兹波段的新型辐射源、无源器件、超分辨率成像及其他领域的应用进行了较为全面的总结和评述,并对该领域未来进一步发展的方向进行了展望。     

Near‐Field Enhanced Plasmonic‐Magnetic Bifunctional Nanotubes for Single Cell Bioanalysis

Near‐field enhanced bifunctional plasmonic‐magnetic (PM) nanostructures consisting of silica nanotubes with embedded solid nanomagnets and uniformly dual‐surface‐coated plasmonic Ag nanoparticles (NPs) are rationally synthesized. The solid embedded sections of nanotubes provide single‐molecule sensitivity with an enhancement factor up to 7.2 × 10⁹ for surface‐enhanced Raman scattering (SERS). More than 2× SERS enhancement is observed from the hollow section compared to the solid section of the same nanotube. The substantial SERS enhancement on the hollow section is attributed to the dual‐sided coating of Ag NPs as well as the near‐field optical coupling of Ag NPs across the nanotube walls. Experimentation and modeling are carried out to understand the dependence of SERS enhancement on the NP sizes, junctions, and the near field effects. By tuning the aspect ratio of the embedded nanomagnets, the magnetic anisotropy of nanotubes can be readily controlled to be parallel or vertical to the long directions for nano‐manipulation. Leveraging the bifunctionality, a nanotube is magnetically maneuvered to a single living mammalian cell amidst many and its membrane composition is analyzed via SERS spectroscopy.     

Plasmonics: Applications to nanoscale terahertz and optical devices

This paper reviews the main physical aspects involved in plasmonic devices, which are considered as a route to subwavelength devices and represents one of the most studied areas of nanophotonics. The paper presents a comprehensive introduction into the various physical mechanisms that generate the surface plasmon polariton—an electromagnetic surface wave confined to the interface between a metal and a dielectric. In this context, basic applications, such as sensors or waveguides, are briefly mentioned. Then, after presenting the main mechanisms for surface plasmon generation and detection, the most important devices based on plasmons are described in detail.     

Maskless Preparation of Spatially-Resolved Plasmonic Nanoparticles on Polydimethylsiloxane via In Situ Fluoride-Assisted Synthesis

Here, a fluoride-assisted route for the controlled in-situ synthesis of metal nanoparticles (NPs) (i.e., AgNPs, AuNPs) on polydimethylsiloxane (PDMS) is reported. The size and coverage of the NPs on the PDMS surface are modulated with time and over space during the synthetic process, leveraging the improved yield (10×) and faster kinetics (100×) of NP formation in the presence of F⁻ ions, compared to fluoride-free approaches. This enables the maskless preparation of both linear and step gradients and patterns of NPs in 1D and 2D on the PDMS surface. As an application in flexible plasmonics/photonics, continuous and step-wise spatial modulations of the plasmonic features of PDMS slabs with 1D and 2D AgNP gradients on the surface are demonstrated. An excellent spatially resolved tuning of key optical parameters, namely, optical density from zero to 5 and extinction ratio up to 100 dB, is achieved with AgNP gradients prepared in AgF solution for 12 minutes; the performance are comparable to those of commercial dielectric/interference filters. When used as a rejection filter in optical fluorescence microscopy, the AgNP-PDMS slabs are able to reject the excitation laser at 405 nm and retain the green fluorescence of microbeads (100 µm) used as test cases.     

Plasma wave electronics: novel terahertz devices using twodimensional electron fluid

We discuss how the propagation of plasma waves in a High Electron Mobility Transistor (HEMT) can be used to implement a new generation of terahertz devices, including sources, resonant detectors, broad band detectors, and frequency multipliers. Our estimates show that these devices should outperform conventional terahertz devices, which use deep submicron Schottky diodes     

太赫兹射频器件与集成技术研究

无线通信、探测感知、安全检测、人工智能等民用和国防电子信息技术的不断快速发展与演进,对太赫兹(0.1～1 THz)技术提出了越来越迫切的应用需求。太赫兹波段具有丰富的频谱带宽资源,其宽带特性可以支撑未来6G高速率通信、新一代高分辨雷达系统性能的实现。同时,太赫兹通信和探测必须克服高频率、短波长所带来的高传播路径衰减、激增的无源器件与互连损耗以及有源器件功率生成和效率难题。本文将回顾太赫兹射频器件与集成技术的发展现状,阐述上海交通大学团队通过新型无源、有源器件与天线及其先进封装等技术方法,整体提升太赫兹前端系统性能的相关研究进展。