In Situ Optical Extinction Measurement for Locally Control of Surface Plasmon Resonance During Nanosecond Laser Irradiation of Silver Ion Exchanged Silicate Glass

Online UV/visible extinction measurement have been achieved during nanosecond Nd:YAG laser irradiation at 532 nm of a silver-exchanged silicate glass after each shot. We have explained the evolution of the integrated spectral evolution with the help of a few observed spots after the laser/glass interaction and completed them by optical and surface measurements. This optical method allows to in situ follow silver ions precipitation in nanoparticles (NPs) and the consequently surface plasmon resonance evolution (SPR). In this study, we focus on the interest of this method for one silver-exchanged soda-lime glass by direct observation of the sample surface. Scanning electron microscopy measurement and optical microscopy were used to identify the various ablation mechanisms. Profilometry was used to evaluate the material distribution and the surface roughness evolution (Rms parameter). Thus, we explain the silver NPs effect on glass matrix at various micrometric scales according to the deposited fluence and silver concentration.     

Luminescence Study of Silver Nanoparticles Obtained by Annealed Ionic Exchange Silicate Glasses

The photoluminescence of silver nanoparticles glasses obtained by ionic exchange and annealing is investigated for various ionic exchange times. These glasses are prepared by immersion of silicate glass samples in a molten salt bath of molar concentration 10% AgNO₃ in NaNO₃ at T = 320 °C. Scanning electron microscopy measurement in electron diffraction scattering (EDS) configuration confirms the silver presence in the various glasses, and the UV/visible absorption gives the evolution of the spectra after ionic exchange and plasmon resonance apparition after annealing. After annealing at 450 °C, both diagnostics inform us about the particles’ formation and the silver rediffusion. Silver nanoparticle growth after annealing prior leads to photoluminescence exaltation and quenching for the longest exchange samples. Subsequently, we propose potential mechanisms of the nanoparticle formation with an initial depolymerization of the silicate network during the ionic exchange and repolymerization during annealing.     

Tailored Aggregate-Free Au Nanoparticle Decorations with Sharp Plasmonic Peaks on a U-Type Optical Fiber Sensor by Nanosecond Laser Irradiation

A novel experimental methodology is presented for fabricating U-shaped optical fiber probes decorated with aggregate-free Au nanoparticles exhibiting sharp localized surface plasmon resonance (LSPR) spectra. The U-type tip is coated with gold nanoparticles (AuNPs) using a simple and time-efficient dip-coating procedure, without initially taking any care to prevent the formation of nanoparticle aggregates in the coated area. In a second step, the coating was irradiated with a few tens of laser pulses of 5-ns duration at 532 nm with intensities in the range of 2–14 MW/cm², leading to the formation of aggregate-free LSPR optical fiber probes. The process was monitored and controlled in real time through the changes induced into the fiber’s extinction spectra by the laser irradiation, and the coated fibers were characterized by electron microscopy. The proposed methodology resulted into the fabrication of U-type optical fiber probes coated with AuNPs exhibiting a sharp plasmon peak, which is a perquisite for their application as sensing devices.     

Correlated Optical Spectroscopy and Electron Microscopy Studies of the Slow Ostwald-Ripening Growth of Silver Nanoparticles under Controlled Reducing Conditions

Metallic nanoparticles display distinct localized surface plasmon resonance (LSPR) properties that depend on their size, shape, and composition and that can be monitored to characterize their growth. Utilizing LSPR properties, we report the first investigation of ambient temperature formation of trioctylamine (TOA)-stabilized spherical silver nanoparticles (AgNPs) of ～3.0-nm diameter by mild reduction of AgClO₄ with the weak reducing agent heptamethyltrisiloxane in organic solvent. The appropriate choice of experimental conditions caused slow reduction, which allowed the study of the nanoparticle growth process by time-resolved UV–visible spectroscopy and transmission electron microscopy (TEM). The linear nanoparticle growth kinetics from 50 min to end of the reaction derived from LSPR changes, the absence of a bimodal size distribution during the initial stage of the reduction process from TEM analysis, and the single crystallinity of the resulting AgNPs suggested a diffusion-controlled Ostwald-ripening growth process. It was also found that in addition to its stabilizing ability, TOA acted as a catalyst and facilitated Ag⁺ reduction. Furthermore, a modest increase in reaction temperature caused a substantial enhancement in the AgNP formation rate, and low concentration of stabilizing ligand yielded an increase in size and dispersity.     

金纳米微粒辅助细胞激光热作用疗法研究

金纳米微粒对可见光的强吸收特性使得光能可以高效地转换为热能.由于金纳米微粒的尺度在几十纳米范围,并且很容易与其他生物体结合,因此可以在局部范围进行激光选择性加热,这非常适合作为分子或细胞的靶向.采用这种金纳米微粒辅助激光热作用方法,对牛肠碱性磷酸酯酶(alkaline phosphatase aP)的选择性破坏,细胞膜的通透性提高以及对细胞的选择性灭活进行了试验并得到了很好的结果.此外,还讨论了用这种方法进行基因转染以及选择性光热治疗一些疾病的可能性.     

Nanosecond Laser-Assisted Fabrication of Colloidal Gold and Silver Nanoparticles and Their Conjugation with S-Ovalbumin

Plasmonics - In the present work, we have investigated the functionalization of protein S-ovalbumin with laser-generated gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) using...     

Morphological and Proteomic Responses of Eruca sativa Exposed to Silver Nanoparticles or Silver Nitrate

Silver nanoparticles (AgNPs) are widely used in commercial products, and there are growing concerns about their impact on the environment. Information about the molecular interaction of AgNPs with plants is lacking. To increase our understanding of the mechanisms involved in plant responses to AgNPs and to differentiate between particle specific and ionic silver effects we determined the morphological and proteomic changes induced in Eruca sativa (commonly called rocket) in response to AgNPs or AgNO₃. Seedlings were treated for 5 days with different concentrations of AgNPs or AgNO₃. A similar increase in root elongation was observed when seedlings were exposed to 10 mg Ag L¹ of either PVP-AgNPs or AgNO₃. At this concentration we performed electron microscopy investigations and 2-dimensional electrophoresis (2DE) proteomic profiling. The low level of overlap of differentially expressed proteins indicates that AgNPs and AgNO₃ cause different plant responses. Both Ag treatments cause changes in proteins involved in the redox regulation and in the sulfur metabolism. These responses could play an important role to maintain cellular homeostasis. Only the AgNP exposure cause the alteration of some proteins related to the endoplasmic reticulum and vacuole indicating these two organelles as targets of the AgNPs action. These data add further evidences that the effects of AgNPs are not simply due to the release of Ag ions.     

Influence of Femtosecond Laser Ablated Silver Nanoparticles on the Nonlinear Optical Properties of Basic Fuchsin dye

We investigate the linear and nonlinear optical properties of Basic Fuchsin influenced by femtosecond laser ablated silver nanoparticles in deionised water. Single beam z-scan technique using a Q-switched Nd:YAG laser (Spectra PhysicsLAB-1760, 532 nm, 7 ns, 10 Hz) is used for the present study. Quenching of fluorescence is observed in the presence of silver nanoparticles. Transmission electron microscopic observation reveals that the nanoparticles are spherical in shape, with an average size of 7 nm. The samples show self-defocusing nonlinearity and better nonlinear absorption behavior in the presence of silver sol. The nonlinear absorption varies with varying input fluence and concentration. The results show that the variations in the nonlinear parameters are also due to the surface plasmon resonance of silver nanoparticles. The nonlinearity of the dye is increased in the presence of silver nanoparticles, which makes the material suitable for various photonic and optoelectronic applications.     

Synthesis and Optical Properties of Highly Stabilized Peptide-Coated Silver Nanoparticles

The interaction between peptide and silver nanoparticle surfaces has been increasingly of interest for bionanotechnology applications. To fully understand how to control such interactions, we have studied the optical properties of peptide-modified silver nanoparticles. However, the impacts of peptide binding motif upon the surface characteristics and physicochemical properties of nanoparticles remain not yet fully understood. Here, we have prepared sodium citrate-stabilized silver nanoparticles and coated with peptide IVD (ID₃). These nanomaterials were characterized by UV-visible, transmission electron microscopy (TEM), and z-potential measurement. The results indicate that silver nanoparticles (AgNP)-peptide interface is generated using ID₃ peptide and suggested that the reactivity of peptide is governed by the conformation of the bound peptide on the nanoparticle surface. The peptide-nanoparticle interactions could potentially be used to make specific functionality into the peptide capped nanomaterials and antibacterial applications.     

Solvent-Induced Morphological Changes of Polyhedral Silver Nanoparticles in Epoxy Resin

The use of just one material as reducing and capping agent during the synthesis of noble metal nanoparticles is of great interest for potential applications. This paper reports a simple method to prepare polyhedral silver nanoparticles at 80 °C using an epoxy resin (Araldite 506) as both reducing and capping agent. The formation of metal nanoparticles was investigated by Fourier-transform infrared spectroscopy, atomic force microscopy, transmission electronic microscopy, high-resolution transmission electronic microscopy and UV-vis spectroscopy. The proposed mechanism for the reduction of silver ions involves radicals as precursors of ketones and other products originated by thermo-oxidation of the resin. The nucleation of small spherical and polyhedral seeds (～7 nm) of polycrystalline silver and twin planes lead to big polyhedral silver nanoparticles of average size, 68 nm. On the other hand, the polyhedral silver nanoparticles dispersed in toluene changed to prolate-like particles, and their dispersion in dimethyl-sulphoxide and formamide originated elongated polyhedrons and concave nanostructures, respectively. These structural changes lead to unusual solvent-induced optical properties. For instance, the polyhedral nanoparticles dispersed in toluene red-shifted their surface plasmon resonance from 425 to 540 nm, in dimethyl-sulphoxide the spectrum exhibited a peak at 418 nm and a shoulder at 520 nm, and for the silver nanoparticles in formamide a broad band with maximum peak at 420 nm was observed. It is showed that the solvent/resin system works itself as structure-directing agent of silver nanoparticles. These results open the doors to achieve silver nanostructures highly sensitive to the dielectric environment, an ideal condition for applications in colorimetric sensors of molecules of biological or chemical interest.     

Substrate Temperature Effect on Microstructure,Optical, and Glucose Sensing Characteristics of Pulsed Laser Deposited Silver Nanoparticles

This work reports the substrate temperature-influenced change in the structural, morphological, optical, and glucose sensing properties of silver (Ag) nanoparticles (NPs) deposited on p-type Si (100) wafers. AgNP films grown at temperatures ranging from RT to 600 °C clearly show a dependence of orientation texture and surface morphology on substrate temperature (T _s). As T _s increases from RT towards 600 °C, the preferred orientation of AgNP film changes from (111) to (200). The AgNPs size, that is T _s-dependent, reaches the maximum value at T _s = 300 °C. This result is attributed to restructuring of AgNPs texture. Moreover, the AgNP shape also changes from ellipsoid to sphere as T _s increases from RT to 600 °C. Surface plasmon enhancement in photoluminescence intensity is observed with increase in T _s. It is found also that the AgNP film deposited at 300 °C has considerable reflectance reduction relative to the silicon substrate, in wavelength range of 300–800 nm and a progressive red shift of localized surface plasmon resonances caused by the adding of increasing quantities of glucose has been observed. As a proof of concept, we also demonstrate the capability of grown AgNP substrates for glucose detection based on surface enhanced Raman spectroscopy in physiological concentration range with short integration time 10 s, varying with T _s.     

Predicting the Size of Silver Nanoparticles from Their Optical Properties

Plasmonics - In this study, localized surface plasmon resonance (LSPR) of the spherical silver nanoparticles (AgNPs) was evaluated based on experimental and theoretical viewpoints. In the...     

Controlled In Situ Seed-Mediated Growth of Gold and Silver Nanoparticles on an Optical Fiber Platform for Plasmonic Sensing Applications

Plasmonics - This study presents an in situ growth technique to develop highly sensitive plasmonic fiber optic sensors with an excellent control over the plasmonic properties of gold (AuNPs) and...     

Rapid Temperature Jump by Infrared Diode Laser Irradiation for Patch-Clamp Studies

Several thermal TRP ion channels have recently been identified. These channels are directly gated by temperature, but the mechanisms have remained elusive. Studies of their temperature gating have been impeded by lack of methods for rapid alteration of temperature in live cells. As a result, only measurements of steady-state properties have been possible. To solve the problem, we have developed an optical approach that uses recently available infrared diode lasers as heat sources. By restricting laser irradiation around a single cell, our approach can produce constant temperature jumps over 50°C in submilliseconds. Experiments with several heat-gated ion channels (TRPV1-3) show its applicability for rapid temperature perturbation in both single cells and membrane patches. Compared with other laser heating approaches such as those by Raman-shifting of the Nd:YAG fundamentals, our approach has the advantage of being cost effective and applicable to live cells while providing an adequate resolution for time-resolved detection of channel activation.     

Laser-Driven Precipitation and Modification of Silver Nanoparticles in Soda Lime Glass Matrix Monitored by On-line Extinction Measurements

In this work, we investigated the effect of nanosecond laser irradiation at 532?nm on precipitation of Ag nanoparticles (NPs) in soda lime glasses doped with silver in the Ag^?+??CNa^?+? ion-exchange process. Formation and subsequent modification of Ag NPs during laser irradiation were studied by on-line extinction measurements making use of the localized surface plasmon resonance (LSPR). These investigations were further completed using scanning and transmission electron microscopies to examine the average size and distribution of nanoparticles within the sample. It has been shown that formation of NPs, its kinetics and the particle size strongly depend on the fluence and the total number of deposited laser pulses. It has been found that Ag NPs form after some specific number of pulses and they rapidly grow in size and number until some maximal value of extinction has been reached. Further irradiation of such samples only results in destruction of precipitated NPs due to photo-breakup, laser ablation confirmed by strong plasma emission observation. Moreover, due to strong irradiation, the host matrix can also be affected by changing its refractive index which manifests as the blue shift of the LSPR.     

Development of LSPR-Based Optical Fiber Dopamine Sensor Using L-Tyrosine-Capped Silver Nanoparticles and Its Nonlinear Optical Properties

Facile synthesis of L-tyrosine-capped silver nanoparticles (Tyr-AgNPs) was carried out, and its linear and nonlinear optical properties were investigated. Further, the sensing properties of Tyr-AgNPs toward dopamine were explored. Tyr-AgNPs exhibit a decrease in fluorescence intensity while a linear increase in absorption spectrum against increase in dopamine (DA) concentration (0–50 μM) at room temperature. Tyr-AgNPs are used as the sensing material for the fabrication of fiber optic dopamine sensor. Sensitivity, selectivity, and limit of detection of the sensor are evaluated. This proposed fiber optic sensor may offer sensitive and low-cost strategy for DA detection.

     

510.6 nm铜蒸汽激光诱导兔血管平滑肌细胞凋亡的形态学观察

目的：透射电镜下观察激光诱导的血管平滑肌细胞（VSMC）凋亡的形态学改变。方法：组织贴块法培养兔主动脉平滑肌细胞,予激光照射（能量密度200J/cm^2、功率密度200mW/cm^2)后4小时、8小时、12小时、16小时、24小时取材,制作电镜标本,于透射电镜下观察,照相并记录实验结果。结果：透射电子显微镜上可观察到自照光后8小时起VSMC依次出现细胞体积缩小,胞质浓缩,细胞核染色质边集,细胞核固缩,凋亡小体形成等改变。结论：经激光照射,VSMC可呈现凋亡细胞典型形态学改变。     

Handling of Iron Oxide and Silver Nanoparticles by Astrocytes

Metal-containing nanoparticles (NPs) are currently used for various biomedical applications. Since such NPs are able to enter the brain, the cells of this organ have to deal with NPs and with NP-derived metal ions. In brain, astrocytes are considered to play a key function in regulating metal homeostasis and in protecting other brain cells against metal toxicity. Thus, among the different types of brain cells, especially astrocytes are of interest regarding the uptake and the handling of metal-containing NPs. This article summarizes the current knowledge on the consequences of an exposure of astrocytes to NPs. Special focus will be given to magnetic iron oxide nanoparticles (IONPs) and silver nanoparticles (AgNPs), since the biocompatibility of these NPs has been studied for astrocytes in detail. Cultured astrocytes efficiently accumulate IONPs and AgNPs in a time-, concentration- and temperature-dependent manner by endocytotic processes. Astrocytes are neither acutely damaged by the exposure to high concentrations of NPs nor by the prolonged intracellular presence of large amounts of accumulated NPs. Although metal ions are liberated from accumulated NPs, NP-derived iron and silver ions are not exported from astrocytes but are rather stored in proteins such as ferritin and metallothioneins which are synthesized in NP-treated astrocytes. The efficient accumulation of large amounts of metal-containing NPs and the upregulation of proteins that safely store NP-derived metal ions suggest that astrocytes protect the brain against the potential toxicity of metal-containing NPs.     

Phosphorus Availability Alters the Effects of Silver Nanoparticles on Periphyton Growth and Stoichiometry

Exposure to silver nanoparticles (AgNPs) may alter the structure and function of freshwater ecosystems. However, there remains a paucity of studies investigating the effects of AgNP exposure on freshwater communities in the natural environment where interactions with the ambient environment may modify AgNP toxicity. We used nutrient diffusing substrates to determine the interactive effects of AgNP exposure and phosphorus (P) enrichment on natural assemblages of periphyton in three Canadian Shield lakes. The lakes were all phosphorus poor and spanned a gradient of dissolved organic carbon availability. Ag slowly accumulated in the exposed periphyton, which decreased periphyton carbon and chlorophyll a content and increased periphyton C:P and N:P in the carbon rich lakes. We found significant interactions between AgNP and P treatments on periphyton carbon, autotroph standing crop and periphyton stoichiometry in the carbon poor lake such that P enhanced the negative effects of AgNPs on chlorophyll a and lessened the impact of AgNP exposure on periphyton stoichiometry. Our results contrast with those of other studies demonstrating that P addition decreases metal toxicity for phytoplankton, suggesting that benthic and pelagic primary producers may react differently to AgNP exposure and highlighting the importance of in situ assays when assessing potential effects of AgNPs in fresh waters.