In Situ Studies of Surface‐Plasmon‐Resonance‐Coupling Sensor Mediated by Stimuli‐Sensitive Polymer Linker

Hybrid plasmonic nanostructures comprising gold nanoparticle (AuNP) arrays separated from Au substrate through a temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) linker layer are constructed, and unique plasmonic‐coupling‐based surface plasmon resonance (SPR) sensing properties are investigated. The optical properties of the model system are investigated by in situ and scan‐mode SPR analysis. The swelling‐shrinking transitions in the polymer linker brush are studied by in situ contact‐mode atomic force microscopy at two different temperatures in water. It is revealed that the thickness of the PNIPAM layer is decreased from 30 to 14 nm by increasing the temperature from 20 to 32 °C. For the first time the dependence of the coupling behavior in AuNPs is investigated with controlled density on the temperature in a quantitative manner in terms of the change in SPR signals. The device containing AuNPs with optimized AuNP density shows 3.2‐times enhanced sensitivity compared with the control Au film‐PNIPAM sample. The refractive index sensing performance of the Au film‐PNIPAM‐AuNPs is greater than that of Au film‐PNIPAM by 19% when the PNIPAM chains have a collapsed conformation above lower critical solution temperature.     

Using a Functional Nanogold Membrane Coupled with Laser Desorption/Ionization Mass Spectrometry to Detect Lead Ions in Biofluids

In this paper, a matrix‐free strategy based on the analysis of nitrocellulose membranes (NCMs) modified with gold nanoparticles (AuNPs) is described, using pulsed‐laser desorption ionization mass spectrometry (LDI‐MS) for comprehensive quantification of lead ions (Pb) with a sub‐nanomolar sensitivity in complicated biofluids. The strong hydrophobic interactions between the NCM and bovine serum albumin (BSA) lead to trapping of BSA‐modified AuNPs (BSA‐AuNPs), resulting in the formation of a nanocomposite film of BSA‐AuNPs on the membrane (BSA‐AuNP/NCM). When the AuNPs interact with thiosulfate (S₂O₃^2?) ions in solution, Au⁺ · S₂O₃^2? complexes form on the AuNP surfaces, facilitating the deposition of Pb atoms in the form of PbAu alloys in the presence of Pb²⁺ ions. The BSA‐AuNP/NCM nanocomposite is a useful LDI‐MS matrix because it allows: i) the soft and enhanced ionization of Pb?Au alloys from the AuNP surfaces; ii) accurate mass measurements (precision: 5 ppm) of Au, Pb, and Au–Pb ions; iii) the extraction of Pb²⁺ ions from very‐dilute aqueous solutions (1.0 × 10^?9 M ); and iv) analyses to be performed directly after the introduction of the substrate into the mass‐analysis LDI spectrometer (i.e., without the need for an elution process). In contrast to the noisy spectra typically obtained when using other AuNP‐assisted LDI approaches, our homogeneous BSA‐AuNP/NCM nanocomposite provides clean mass spectra with fewer and weaker signals from AuNP‐associated interfering species. As a result, the BSA‐AuNP/NCM substrates allow sensitive LDI‐MS detection of analytes with low mass‐to‐charge ratios. Under optimal conditions, this LDI‐MS approach provides high sensitivity, a wide dynamic detection range (1.0 × 10^?9–5.0 × 10^?6 M ), and a high selectivity toward Pb²⁺ ions (with at least a 100‐fold concentration tolerance relative to other metal ions). The BSA‐AuNP/NCM nanocomposite also provides excellent shot‐to‐shot (<5%) and sample‐to‐sample (<5%) reproducibilities of ion production because of its homogeneous substrate surface, thereby enabling LDI‐based measurements to a consistent quantification of Pb²⁺ ions in real samples (e.g., urine, whole blood).     

Ultrasonication‐Induced Self‐Assembled Fixed Nanogap Arrays of Monomeric Plasmonic Nanoparticles inside Nanopores

Monomeric gold (Au) and silver (Ag) nanoparticle (NP) arrays are self‐assembled uniformly into anodized aluminium oxide (AAO) nanopores with a high homogeneity of greater than 95%, using ultrasonication. The monomeric metal NP array exhibits asymmetric plasmonic absorption due to Fano‐like resonance as interpreted by finite‐difference time‐domain (FDTD) simulation for the numbers up to 127 AuNPs. To examine gap distance‐dependent collective‐plasmonic resonance, the different dimensions of S, M, and L arrays of the AuNP diameters/the gap distances of ≈36 nm/≈66 nm, ≈45 nm/≈56 nm, and ≈77 nm/≈12 nm, respectively, are prepared. Metal NP arrays with an invariable nanogap of ≈50 nm can provide consistent surface‐enhanced Raman scattering (SERS) intensities for Rhodamine 6G (Rh6G) with a relative standard deviation (RSD) of 3.8–5.4%. Monomeric arrays can provide an effective platform for 2D hot‐electron excitation, as evidenced by the SERS peak‐changes of 4‐nitrobenzenethiol (4‐NBT) adsorbed on AgNP arrays with a power density of ≈0.25 mW µm^‐2 at 514 and 633 nm. For practical purposes, the bacteria captured by 4‐mercaptophenylboronic acid are found to be easily destroyed under visible laser excitation at 514 nm with a power density of ≈14 mW µm^‐2 for 60 min using Ag due to efficient plasmonic‐electron transfer.     

Poled Sol–Gel Materials With Heterocycle Push–Pull Chromophores that Confer Enhanced Second‐Order Optical Nonlinearity

Hybrid organic–inorganic materials doped with zwitterionic push–pull chromophores with high hyperpolarizability have been synthesized by a sol–gel procedure. A large chromophore concentration was reached by using N‐(hydroxyethyl)carbazole as a physical spacer (preventing the dye aggregation). Spin‐coated doped films were electrically poled and second harmonic generation measurements performed in situ. During the thermally assisted poling under a N₂ atmosphere, only the carbazole molecules degraded. Second‐harmonic generation measurements gave an estimation of the nonlinear coefficient, r₃₃, of 38 pm V^–1 at 1064 nm.     

Third‐Order Nonlinear Optical Response of Gold‐Island Films

Films of gold nanoscaled islands with thicknesses ranging between 0.5 and 15 nm were prepared by thermal evaporation onto untreated and aminosilane‐pretreated glass substrates. Post‐deposition annealing was found to modify the morphological characteristics of the islands (e.g., average island area and height, inter‐island distance, etc.), resulting in changes of the localized surface plasmon resonance (SPR) characteristics and, therefore, modifying the nonlinear optical (NLO) response of the films. The NLO response of both unannealed and annealed (20 h at 200 °C) films was studied by means of the optical Kerr effect (OKE), using 35 ps, 532 nm laser excitation, while measurements performed by means of the Z‐scan technique allowed for the determination of both the nonlinear refraction and absorption characteristics of the films. The results are discussed and compared with other reports.     

Gold Nanoparticle–Colloidal Carbon Nanosphere Hybrid Material: Preparation,Characterization, and Application for an Amplified Electrochemical Immunoassay

A rapid microwave‐hydrothermal method has been developed to prepare monodisperse colloidal carbon nanospheres from glucose solution, and gold nanoparticles (AuNPs) are successfully assembled on the surface of the colloidal carbon nanospheres by a self‐assembly approach. The resulting AuNP/colloidal carbon nanosphere hybrid material (AuNP/C) has been characterized and is expected to offer a promising template for biomolecule immobilization and biosensor fabrication because of its satisfactory chemical stability and the good biocompatibility of AuNPs. Herein, as an example, it is demonstrated that the as‐prepared AuNP/C hybrid material can be conjugated with horseradish peroxidase‐labeled antibody (HRP‐Ab₂) to fabricate HRP‐Ab₂‐AuNP/C bioconjugates, which can then be used as a label for the sensitive detection of protein. The amperometric immunosensor fabricated on a carbon nanotube‐modified glass carbon electrode was very effective for antibody immobilization. The approach provided a linear response range between 0.01 and 250 ng mL^?1 with a detection limit of 5.6 pg mL^?1. The developed assay method was versatile, offered enhanced performances, and could be easily extended to other protein detection as well as DNA analysis.     

Gadolinium‐Doped Iron Oxide Nanoprobe as Multifunctional Bioimaging Agent and Drug Delivery System

In this study, a high‐performance T₁–T₂ dual‐model contrast agent by gadolinium‐doped iron oxide nanoparticle (GION) is developed. Following its development, the application of this agent in vivo by combining doxorubicin (DOX) and folic acid (FA) (FA–GION–DOX) for targeted drug delivery to monitor cancer treatment is explored. GION showed transverse and longitudinal relaxivities up to 182.7 × 10^?3 and 7.87 × 10^?3m ^?1 s^?1, respectively, upon Gd/Fe ratio in GION at 1/4. DOX released from FA–GION–DOX is pH dependent and only kills cancer cell after FA receptor‐mediated internalization into the acidic environment of endosomes and lysosomes. Systemic delivery of FA–GION–DOX significantly inhibits the growth of tumors and shows good magnetic resonance enhancement in a human cervical cancer xenograft model. Thus, FA–GION–DOX has a potential application for the targeted and magnetic resonance imaging guided therapy of cervical cancer.     

Giant Nonlinear Optical Absorption of Ion-Intercalated Tin Disulfide Associated with Abundant In-Gap Defects

Herein it is reported that electrochemical ion-intercalation is a convenient and effective strategy toward materials with giant nonlinear optical (NLO) absorption. Alkali-metal ions (i.e., Li⁺, Na⁺, K⁺) are electrochemically intercalated into SnS₂ nanosheets. All ion-intercalated samples exhibit remarkably enhanced optical nonlinearity compared with an untreated sample, and Li-intercalated SnS₂ (Li_0.952Sn^II_0.398Sn^IV_0.563S₂) possesses optimized strong NLO performance. Li_0.952Sn^II_0.398Sn^IV_0.563S₂ exhibits strong saturable absorption, and the corresponding nonlinear absorption coefficient (β_eff) is -1.7 × 10⁴ cm GW^–1 for the laser excitation at 515 nm. Li_0.952Sn^II_0.398Sn^IV_0.563S₂ shows prominent reverse saturable absorption with the laser excitation at 800 nm (β_eff: 2.8 × 10⁴ cm GW^–1) and 1030 nm (β_eff: 1.4 × 10⁴ cm GW^–1). All β_eff values are larger than most of the reported inorganic NLO materials at corresponding wavelengths. The optical limiting threshold of Li_0.952Sn^II_0.398Sn^IV_0.563S₂ is 8 × 10^–4 J cm^–2, two orders of magnitude smaller (better) than the bench-mark composite (e.g., SWNT-NH-TPP). Ion intercalation introduces abundant in-gap defects. The excitation of electrons in in-gap states to conduction band intensifies the Pauli-blocking effect and therefore promotes the saturable absorption under the 515 nm laser excitation, while the in-gap defect states acting as effective excitation pathway facilitate excited-state absorption for 800 and 1030 nm laser.     

Ionic‐Liquid‐Doped Polyaniline Inverse Opals: Preparation,Characterization, and Application for the Electrochemical Impedance Immunoassay of Hepatitis B Surface Antigen

A 3D ordered macroporous (3DOM) ionic‐liquid‐doped polyaniline (IL‐PANI) inverse opaline film is fabricated with an electropolymerization method and gold nanoparticles (AuNPs) are assembled on the film by electrostatic adsorption, which offers a promising basis for biomolecular immobilization due to its satisfactory chemical stability, good electronic conductivity, and excellent biocompatibility. The AuNP/IL‐PANI inverse opaline film could be used to fabricate an electrochemical impedance spectroscopy (EIS) immunosensor for the determination of Hepatitis B surface antigen (HBsAg). The concentration of HBsAg is measured using the EIS technique by monitoring the corresponding specific binding between HBsAg and HBsAb (surface antibody). The increased electron transfer resistance (R_et) values are proportional to the logarithmic value of the concentration of HBsAg. This novel immunoassay displays a linear response range between 0.032 pg mL^?1 and 31.6 pg mL^?1 with a detection limit of 0.001 pg mL^?1. The detection of HBsAg levels in several sera showed satisfactory agreement with those using a commercial turbidimetric method.     

Induced SER‐Activity in Nanostructured Ag–Silica–Au Supports via Long‐Range Plasmon Coupling

A novel Ag–silica–Au hybrid device is developed that displays a long‐range plasmon transfer of Ag to Au leading to enhanced Raman scattering of molecules largely separated from the optically excited Ag surface. A nanoscopically rough Ag surface is coated by a silica spacer of variable thickness from ～1 to 21 nm and a thin Au film of ～25 nm thickness. The outer Au surface is further functionalized by a self‐assembled monolayer (SAM) for electrostatic binding of the heme protein cytochrome c (Cyt c) that serves as a Raman probe and model enzyme. High‐quality surface‐enhanced resonance Raman (SERR) spectra are obtained with 413 nm excitation, demonstrating that the enhancement results exclusively from excitation of Ag surface plasmons. The enhancement factor is estimated to be 2 × 10⁴–8 × 10³ for a separation of Cyt c from the Ag surface by 28–47 nm, corresponding to an attenuation of the enhancement by a factor of only 2–6 compared to Cyt c adsorbed directly on a SAM‐coated Ag electrode. Upon immobilization of Cyt c on the functionalized Ag–silica–Au device, the native structure and redox properties are preserved as demonstrated by time‐ and potential‐dependent SERR spectroscopy.     

High‐Sensitivity Floating‐Gate Phototransistors Based on WS2 and MoS2

In recent years, 2D layered materials have been considered as promising photon absorption channel media for next‐generation phototransistors due to their atomic thickness, easily tailored single‐crystal van der Waals heterostructures, ultrafast optoelectronic characteristics, and broadband photon absorption. However, the photosensitivity obtained from such devices, even under a large bias voltage, is still unsatisfactory until now. In this paper, high‐sensitivity phototransistors based on WS₂ and MoS₂ are proposed, designed, and fabricated with gold nanoparticles (AuNPs) embedded in the gate dielectric. These AuNPs, located between the tunneling and blocking dielectric, are found to enable efficient electron trapping in order to strongly suppress dark current. Ultralow dark current (10^?11 A), high photoresponsivity (1090 A W^?1), and high detectivity (3.5 × 10¹¹ Jones) are obtained for the WS₂ devices under a low source/drain and a zero gate voltage at a wavelength of 520 nm. These results demonstrate that the floating‐gate memory structure is an effective configuration to achieve high‐performance 2D electronic/optoelectronic devices.     

Optical and Electrical Enhancement of Hydrogen Evolution by MoS2@MoO3 Core–Shell Nanowires with Designed Tunable Plasmon Resonance

The design of transition‐metal chalcogenides (TMCs) photocatalysts for water splitting is highly important, in which both light absorption and interfacial engineering play vital roles in photoexcited electron generation, electron transport, and ultimately speeding up water splitting. To this end, plasmonic metal nanomaterials with surface plasmon resonances are promising candidates. However, it is very difficult to enhance the light absorption and manage the interfacial engineering simultaneously, thus, resulting in suboptimal photocatalytic performance. Here, a doped semiconductor plasmon is proposed to optically and electrically enhance TMCs hydrogen evolution. With the tunability of plasmon resonance in a doped MoO₃ semiconductor via hydrogen reduction, the broadband absorption and good interfacial engineering are simultaneously demonstrated in flexible MoS₂@MoO₃ core–shell nanowire photocatalysts. Better energy‐band alignment with MoS₂ can also be realized, thereby achieving improved photoinduced electron generation. More importantly, the defects at the interface between MoO₃ and MoS₂ are effectively reduced because of precise tunability of plasmon resonance, which enhances electron transport. As a proof of concept, this optimized hybrid nanostructure exhibits outstanding H₂ evolution characteristics (841.4 μmol h^?1 g^?1), excellent stability, and good flexibility. The value is also one of the highest hydrogen evolution activity rates to date among the two dimensional‐layered visible‐light photocatalysts.     

Selenide Glass Optical Fiber Doped with Pr3+ for U‐Band Optical Amplifier

Pr³⁺‐doped selenide glass optical fiber, which guarantees single‐mode propagation of above at least 1310 nm, has been successfully fabricated using a Ge‐Ga‐Sb‐Se glass system. Thermal properties such as glass transition temperature and viscosity of the glasses have been analyzed to find optimum conditions for fiber drawing. Attenuation loss incorporating the effects of an electronic band gap transition, Rayleigh scattering, and multiphonon absorption has also been theoretically estimated for the Ge‐Ga‐Sb‐Se fiber. A conventional double crucible technique has been applied to fabricate the selenide fiber. The background loss of the fiber was estimated to be approximately 0.64 dB/m at 1650 nm, which can be considered fairly good. When excited at approximately 1470 nm, Pr³⁺‐doped selenide fiber resulted in amplified spontaneous emission and saturation behavior with increasing pump power in a U‐band wavelength range of 1625 to 1675 nm.     

Photorefractive Performance of Hyperstructured Cyclotriphosphazene Molecular Glasses containing Carbazole Moieties

Two hyperstructured photorefractive (PR) molecular glasses ( M1 and M2 ) with a cyclotriphosphazene core are synthesized via nucleophilic substitution and an azo‐coupling reaction. These molecules exhibit excellent solubility in common organic solvents and maintain a complete amorphous state in spite of their high glass‐transition temperature. The nonlinear optical effects, two‐beam coupling and four‐wave mixing, respectively, are used to prove the PR performance in the optically transparent films of M1 and M2 doped with 30 % N‐ethyl‐carbazole. With no external electric field, a gain coefficient of 102 cm^–1 and diffraction efficiency of 24 % are obtained in the composite made from M1 , and an even higher gain coefficient of 214 cm^–1 and diffraction efficiency of 31 % are obtained in the composite made from M2 owing to its higher chromophore loading.     

Ag纳米颗粒对Er3+/Tm3+/Yb3+共掺铋锗酸盐玻璃上转换发光特性的影响

采用传统熔融淬冷法制备了系列Er³⁺/Tm 3+/Yb³⁺共掺复合Ag纳米颗粒的铋锗酸盐玻璃样品。从吸收光谱中 确定了Ag纳米颗粒表面等离子体共振(SPR)峰位于545nm附近;透射 电镜(TEM)图像中观察到均匀分布的Ag纳米颗粒,尺寸 约为6～18nm。研究了纳米Ag含量对Er3＋/Tm3＋ 共掺复合Ag纳米颗粒铋锗酸盐玻璃上转换发光特性的影响,结果表 明,Tm³⁺离子472nm处的上转换蓝光、Er³⁺离子525nm处的上转换绿光、543nm处的上转换 绿光和661nm处的上转换红光发光强度在AgCl含量的质量百分数为 1%时达到最大值,与未掺杂AgCl的基质玻璃相比,分别提高了约3.2、3.8、5.4倍。     

Plasmonic Enhancement or Energy Transfer? On the Luminescence of Gold‐, Silver‐, and Lanthanide‐Doped Silicate Glasses and Its Potential for Light‐Emitting Devices

With the technique of synchrotron X‐ray activation, molecule‐like, non‐plasmonic gold and silver particles in soda‐lime silicate glasses can be generated. The luminescence energy transfer between these species and lanthanide(III) ions is studied. As a result, a significant lanthanide luminescence enhancement by a factor of up to 250 under non‐resonant UV excitation is observed. The absence of a distinct gold and silver plasmon resonance absorption, respectively, the missing nanoparticle signals in previous SAXS and TEM experiments, the unaltered luminescence lifetime of the lanthanide ions compared to the non‐enhanced case, and an excitation maximum at 300–350 nm (equivalent to the absorption range of small noble metal particles) indicate unambiguously that the observed enhancement is due to a classical energy transfer between small noble metal particles and lanthanide ions, and not to a plasmonic field enhancement effect. It is proposed that very small, molecule‐like noble metal particles (such as dimers, trimers, and tetramers) first absorb the excitation light, undergo a singlet‐triplet intersystem crossing, and finally transfer the energy to an excited multiplet state of adjacent lanthanide(III) ions. X‐ray lithographic microstructuring and excitation with a commercial UV LED show the potential of the activated glass samples as bright light‐emitting devices with tunable emission colors.     

Zr‐Doped Indium Oxide (IZRO) Transparent Electrodes for Perovskite‐Based Tandem Solar Cells

Parasitic absorption in transparent electrodes is one of the main roadblocks to enabling power conversion efficiencies (PCEs) for perovskite‐based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device. Here, the excellent properties of Zr‐doped indium oxide (IZRO) transparent electrodes for such applications, with improved near‐infrared (NIR) response, compared to conventional tin‐doped indium oxide (ITO) electrodes, are shown. Optimized IZRO films feature a very high electron mobility (up to ≈77 cm² V^?1 s^?1), enabling highly infrared transparent films with a very low sheet resistance (≈18 Ω □^?1 for annealed 100 nm films). For devices, this translates in a parasitic absorption of only ≈5% for IZRO within the solar spectrum (250–2500 nm range), to be compared with ≈10% for commercial ITO. Fundamentally, it is found that the high conductivity of annealed IZRO films is directly linked to promoted crystallinity of the indium oxide (In₂O₃) films due to Zr‐doping. Overall, on a four‐terminal perovskite/silicon tandem device level, an absolute 3.5 mA cm^?2 short‐circuit current improvement in silicon bottom cells is obtained by replacing commercial ITO electrodes with IZRO, resulting in improving the PCE from 23.3% to 26.2%.     

Symmetric and Asymmetric Conjugated 3,3′‐Bipyridine Derivatives as a New Class of Third‐Order NLO Chromophores with an Enhanced Non‐resonant,Nonlinear Refractive Index in the Picosecond Range

We report on the synthesis and third‐order nonlinear optical (NLO) properties of new asymmetric (push–pull) and symmetric chromophores based on the 3,3′‐bipyridine core. The nonlinear refraction as well as the linear and nonlinear absorption of these compounds has been studied, in solution, by spectroscopy and picosecond single‐shot Z‐scan measurements. The results are very promising in terms of non‐resonant, nonlinear refractive index in the near infrared, particularly with enhancement of the (nonlinear efficiency/transparency) trade‐off afforded by the symmetrization of the chromophores. A new polymer with this structural design has also been investigated.     

Phonon–plasmon coupling in Si doped GaN nanowires

The vibrational properties of silicon doped GaN nanowires with diameters comprised between 40 and 100 nm are studied by Raman spectroscopy through excitation with two different wavelengths: 532 and 405 nm. Excitation at 532 nm does not allow the observation of the coupled phonon–plasmon upper mode for the intentionally doped samples. Yet, excitation at 405 nm results in the appearance of a narrow peak at frequencies close to that of the uncoupled A₁(LO) mode for all samples. This behavior points to phonon–plasmon scattering mediated by large phonon wave-vector in these thin and highly doped nanowires.     

Plasmon Mediated Near-Field Energy Transfer From Solid-State,Electrically Injected Excitons to Solution Phase Chromophores

An organic diode is demonstrated that near-field energy transfers to molecules in solution via surface plasmon polaritons, in contrast to typical far-field excitation via absorption of traveling photons. Electrically generated excitons couple to surface plasmon modes in the cathode; the plasmons subsequently excite chromophore molecules on top of the cathode. External quantum efficiency and time resolved photoluminescence measurements are used to characterize the diode and the near-field energy transfer process. In addition, it is shown that excited chromophores can charge-transfer to quencher molecules, illustrating the potential of this device to be used for photochemical applications.