Here, carbon nanodots synthesized from β-alanine (Ala-CDs) and detonation nanodiamonds (NDs) were assessed using (1) radiolabeled excitatory neurotransmitters L-[14C]glutamate, D-[2,33H]aspartate, and inhibitory ones [3H]GABA, [3H]glycine for registration of their extracellular concentrations in rat cortex nerve terminals; (2) the fluorescent ratiometric probe NR12S and pH-sensitive probe acridine orange for registration of the membrane lipid order and synaptic vesicle acidification, respectively; (3) suspended bilayer lipid membrane (BLM) to monitor changes in transmembrane current. In nerve terminals, Ala-CDs and NDs increased the extracellular concentrations of neurotransmitters and decreased acidification of synaptic vesicles, whereas have not changed sufficiently the lipid order of membrane. Both nanoparticles, Ala-CDs and NDs, were capable of increasing the conductance of the BLM by inducing stable potential-dependent cation-selective pores. Introduction of divalent cations, Zn2+ or Cd2+ on the particles` application side (cis-side) increased the rate of Ala-CDs pore-formation in the BLM. The application of positive potential (+100 mV) to the cis-chamber with Ala-CDs or NDs also activated the insertion as compared with the negative potential (?100 mV). The Ala-CD pores exhibited a wide-range distribution of conductances between 10 and 60 pS and consecutive increase in conductance of each major peak by ~10 pS, which suggest the clustering of the same basic ion-conductive structure. NDs also formed ion-conductive pores ranging from 6 pS to 60 pS with the major peak of conductance at ~12 pS in cholesterol-containing membrane. Observed Ala-CDs and NDs-induced increase in transmembrane current coincides with disturbance of excitatory and inhibitory neurotransmitter transport in nerve terminals. 相似文献
A new optical sensor based on the localized surface plasmon resonance (LSPR) in 2D arrays of silver nanoparticles (AgNPs) combined with a differential optical measurement method is developed. LSPR substrates comprised of self-assembled, 2D arrays of AgNPs exhibit coherent plasmon coupling manifested as a sharp peak in the blue spectral region. A bottom-up approach was used to fabricate reproducible and cost-effective substrates with a figure of merit (FOM) of ~24. The LSPR shift was determined by measuring the difference between light extinction at two wavelengths selected on each side of the sharp peak. The sharpness of the coherent plasmon resonance together with the differential measurement method enabled a record sensing resolution in bulk for a LSPR sensor of ~4.8E-6 RIU. 相似文献
An immunoassay method based on the peak shift of the localized surface plasmon resonance (LSPR) absorption maxima has been developed for the determination of the thyroid stimulating hormone (TSH) in human blood serum. The anti-TSH antibody was adsorbed on the synthesized gold nanoparticles by electrostatic forces. The efficiency of the nanobiosensor was improved by optimizing the factors affecting the probe construction such as the pH and the antibody to gold nanoparticles ratio. Dynamic light scattering was applied for the characterization of the constructed probe. The amount of peak shift of the LSPR absorption maxima was selected as the basis for determination of TSH antigen. The linear dynamic range of 0.4–12.5 mIU L−1 and the calibration sensitivity of 1.71 L mIU−1 were obtained. The human control serum sample was analyzed for TSH by constructed nanobiosensor and the acceptable results were obtained. 相似文献
Four intense and separate localized surface plasmon resonance (LSPR) absorption peaks have been obtained in the gold-dielectric–gold–silver multilayer nanoshells. The silver coating on the gold shell results in a new LSPR peak at about 400 nm corresponding to the $ {{\left| {\omega_{+}^{-}} \right\rangle}_{Ag }} $ mode. The intense local electric field concentrated in the silver shell at the wavelength of 400 nm indicates that this new plasmonic band is coming from the symmetric coupling between the antibonding silver shell plasmon mode and the inner sphere plasmon. Increasing the silver shell thickness also leads to the intensity increasing of the $ {{\left| {\omega_{+}^{-}} \right\rangle}_{Au }} $ mode and blue shift of $ \left| {\omega_{-}^{+}} \right\rangle $ and $ \left| {\omega_{-}^{-}} \right\rangle $ modes. Therefore, quadruple intense plasmonic resonances in the visible region could be achieved in gold-dielectric–gold–silver multilayer nanoshells by tuning the geometrical parameters. And the quadruple intense plasmonic resonances in the visible region provide well potential for multiplex biosensing based on LSPR. 相似文献
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. 相似文献
In this paper, we investigate the ability of the gold nanorods (GNRs) to detect some proteins and demonstrate their potential to be used as plasmonic nanobiosensors. The GNRs were synthesized by a two-step seed-mediated growth procedure at room temperature. Firstly, a seed solution of gold nanoparticles was synthesized in the presence of cetyltrimethylammonium bromide surfactant and, subsequently, incorporated with appropriate amount of silver nitrate and tetrachloroauric acid solutions to grow GNRs with average length of 50 nm and diameter of 14 nm. We study the interaction of GNRs with proteins whose molecular weight varies from 6.5 up to 75 kDa. We investigate the resulting solutions by means of UV–vis absorption spectroscopy to determine the effect of the proteins characteristics on the shift of the localized surface plasmon resonance (LSPR). We show that for the case when proteins are in large excess compared to the GNRs concentration, whatever the protein is, the LSPR shift is constant and does not depend on the protein molecular weight. Moreover, we have been able to demonstrate that the sensitivity of such LSPR sensor is around 10–9 M/nm on a concentration range from 10–10 to 10–8 M. Some comparison with finite-difference time-domain simulations have also shown that the number of proteins adsorbed at the GNRs surface is around 40. 相似文献
Nanodiscs (NDs) are an excellent alternative to small unilamellar vesicles (SUVs) for studies of membrane protein structure, but it has not yet been shown that membrane proteins are able to spontaneously fold and insert into a solution of freely diffusing NDs. In this article, we present SDS-PAGE differential mobility studies combined with fluorescence, circular dichroism, and ultraviolet resonance Raman spectroscopy to confirm the spontaneous folding of outer membrane protein A (OmpA) into preformed NDs. Folded OmpA in NDs was incubated with Arg-C protease, resulting in the digestion of OmpA to membrane-protected fragments with an apparent molecular mass of ∼26 kDa (major component) and ∼24 kDa (minor component). The OmpA folding yields were greater than 88% in both NDs and SUVs. An OmpA adsorbed intermediate on NDs could be isolated at low temperature and induced to fold via an increase in temperature, analogous to the temperature-jump experiments on SUVs. The circular dichroism spectra of OmpA in NDs and SUVs were similar and indicated β-barrel secondary structure. Further evidence of OmpA folding into NDs was provided by ultraviolet resonance Raman spectroscopy, which revealed the intense 785 cm−1 structural marker for folded OmpA in NDs. The primary difference between folding in NDs and SUVs was the kinetics; the rate of folding was two- to threefold slower in NDs compared to in SUVs, and this decreased rate can tentatively be attributed to the properties of NDs. These data indicate that NDs may be an excellent alternative to SUVs for folding experiments and offer benefits of optical clarity, sample homogeneity, control of ND:protein ratios, and greater stability. 相似文献
Gold nanoring array surfaces that exhibit strong localized surface plasmon resonances (LSPR) at near infrared (NIR) wavelengths from 1.1 to 1.6 μm were used as highly sensitive real-time refractive index biosensors. Arrays of gold nanorings with tunable diameter, width, and spacing were created by the nanoscale electrodeposition of gold nanorings onto lithographically patterned nanohole array conductive surfaces over large areas (square centimeters). The bulk refractive index sensitivity of the gold nanoring arrays was determined to be up to 3,780 cm−1/refractive index unit by monitoring shifts in the LSPR peak by FT-NIR transmittance spectroscopy measurements. As a first application, the surface polymerization reaction of dopamine to form polydopamine thin films on the nanoring sensor surface from aqueous solution was monitored with the real-time LSPR peak shift measurements. To demonstrate the utility of the gold nanoring arrays for LSPR biosensing, the hybridization adsorption of DNA-functionalized gold nanoparticles onto complementary DNA-functionalized gold nanoring arrays was monitored. The adsorption of DNA-modified gold nanoparticles onto nanoring arrays modified with mixed DNA monolayers that contained only 0.5 % complementary DNA was also detected; this relative surface coverage corresponds to the detection of DNA by hybridization adsorption from a 50 pM solution.
Essential oil of Carum copticum seeds, obtained from a local shop, was extracted and content of thymol was analyzed using square-wave voltammetry at boron-doped diamond electrode. The effect of various parameters, such as pH of supporting electrolyte and square-wave voltammetric parameters (modulation amplitude and frequency), was examined. In Britton–Robinson buffer solution (pH 4), thymol provided a single and oval-shaped irreversible oxidation peak at +1.13 V versus silver/silver chloride potassium electrode (3 M). Under optimal experimental conditions, a plot of peak height against concentration of thymol was found to be linear over the range of 4 to 100 μM consisting of two linear ranges: from 4 to 20 μM (R2 = 0.9964) and from 20 to 100 μM (R2 = 0.9993). The effect of potential interferences such as p-cymene and γ-terpinene (major components in essential oil of C. copticum seeds) was evaluated. Thus, the proposed method displays a sufficient selectivity toward thymol with a detection limit of 3.9 μM, and it was successfully applied for the determination of thymol in essential oil of C. copticum seeds. The Prussian blue method was used for validation of the proposed electroanalytical method. 相似文献
Background and Aims Conservation of the genetic diversity afforded by recalcitrant seeds is achieved by cryopreservation, in which excised embryonic axes (or, where possible, embryos) are treated and stored at temperatures lower than −180 °C using liquid nitrogen. It has previously been shown that intracellular ice forms in rapidly cooled embryonic axes of Acer saccharinum (silver maple) but this is not necessarily lethal when ice crystals are small. This study seeks to understand the nature and extent of damage from intracellular ice, and the course of recovery and regrowth in surviving tissues.Methods Embryonic axes of A. saccharinum, not subjected to dehydration or cryoprotection treatments (water content was 1·9 g H2O g−1 dry mass), were cooled to liquid nitrogen temperatures using two methods: plunging into nitrogen slush to achieve a cooling rate of 97 °C s−1 or programmed cooling at 3·3 °C s−1. Samples were thawed rapidly (177 °C s−1) and cell structure was examined microscopically immediately, and at intervals up to 72 h in vitro. Survival was assessed after 4 weeks in vitro. Axes were processed conventionally for optical microscopy and ultrastructural examination.Key Results Immediately following thaw after cryogenic exposure, cells from axes did not show signs of damage at an ultrastructural level. Signs that cells had been damaged were apparent after several hours of in vitro culture and appeared as autophagic decomposition. In surviving tissues, dead cells were sloughed off and pockets of living cells were the origin of regrowth. In roots, regrowth occurred from the ground meristem and procambium, not the distal meristem, which became lethally damaged. Regrowth of shoots occurred from isolated pockets of surviving cells of peripheral and pith meristems. The size of these pockets may determine the possibility for, the extent of and the vigour of regrowth.Conclusions Autophagic degradation and ultimately autolysis of cells following cryo-exposure and formation of small (0·2–0·4 µm) intracellular ice crystals challenges current ideas that ice causes immediate physical damage to cells. Instead, freezing stress may induce a signal for programmed cell death (PCD). Cells that form more ice crystals during cooling have faster PCD responses. 相似文献
Gold–silver core–shell triangular nanoprisms (Au/AgTNPs) were grown onto transparent indium tin oxide (ITO) thin film-coated glass substrate through a seed-mediated growth method without using peculiar binder molecules. The resulting Au/AgTNPs were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, UV–vis spectroscopy, and cyclic voltammograms. The peak of dipolar plasmonic resonance was located at near infrared region of ~700 nm, which showed the refractive index (RI) sensitivity of 248 nm/RIU. Moreover, thin gold shells were electrodeposited onto the surface of Au/AgTNPs in order to stabilize nanoparticles. Compared with the Au/AgTNPs, this peak of localized surface plasmon resonance (LSPR) was a little red-shift and decreased slightly in intensity. The refractive index sensitivity was estimated to be 287 nm/RIU, which showed high sensitivity as a LSPR sensing platform. Those triangular nanoprisms deposited on the ITO substrate could be further functionalized to fabricate LSPR biosensors. Results of this research show a possibility of improving LSPR sensor by using core–shell nanostructures. 相似文献
The objective of this study was to evaluate the effect of the light emitting diode (LED) spectra on the antioxidant properties
of sprouted wheat (Triticum aestivum L.), radish (Raphanus sativus L.), and lentil (Lens esculenta Moenh.) seeds. Lighting experiments were performed under controlled conditions (PPFD - 100 μmol m−2 s−1; 12 h photoperiod; 27°C). The LED conditions used were: L1 - 638 nm; L2 - 455 nm, 638 nm, 669 nm, 731 nm (basal components);
L3 - basal + 385 nm; L4 - basal + 510 nm and L5 - basal + 595 nm. Wheat and lentil sprouts were shown to accumulate less phenolic
compounds and were more sensitive to light spectral differences when compared to radish sprouts. The antioxidant properties
and contents of antioxidant compounds in seeds germinated in the dark were significantly lower than LED treated seeds. The
higher content of total phenols and significant increase in alpha-tocopherol and vitamin C concentration resulted in altered
DPPH free-radical scavenging capacity. Therefore we conclude that the LED spectra, based on basal components supplemented
with green (510 nm) light can improve the antioxidant properties of sprouted seeds of lentil and wheat. The highest antioxidant
properties of radish seeds were caused by radiation with supplemental amber (595 nm) light. 相似文献
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. 相似文献
Label-free detection of biomarkers has been recently noticed and optical biosensors showed great potential to be the method of choice in such situation. Here, we used glancing angle deposition (GLAD) method in which silver nano-columns stabilized by a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (MUA) and 6-mercaptohexanol to investigate the capability of localized surface plasmon resonance (LSPR)–based silver nanochips to detect prostate-specific antigen (PSA). Using different standard solutions of PSA, limit of detection (LOD) of the nano-sensors has been calculated to be 850 pg/ml. The selectivity of the nano-sensors has also been evaluated. We showed that these nano-sensors could detect PSA in clinically acceptable sensitivity and specificity without any complicated laboratory equipment.
Neurological disorders (NDs) are one of the leading causes of death especially in the developed countries. Among those NDs, Alzheimer’s disease (AD) and Parkinson disease (PD) are heading the table. There have been several reports in the scientific literatures which suggest the linkage between cardiovascular disorders (CVDs) and NDs. In the present communication, we have tried to compile NDs (AD and PD) association with CVDs reported in the literature. Based on the available scientific literature, we believe that further comprehensive study needs to be done to elucidate the molecular linking points associated with the above mentioned disorders.Abbreviations: AD, Alzheimer’s disease, Aβ, β amyloid, PD, Parkinson disease, l-DOPA, l-dihydroxyphenylalanine, LBs, Lewy bodies, DA, dopamine, APP, amyloid precursor protein, CVD, cardiovascular disease相似文献
We report a simple route to design highly sensitive triangular silver nanoplates (TSNPs)-based SERS substrate for the trace-level detection of explosive molecules. The size-dependent localized surface plasmon resonance (LSPR) tunability for the synthesis of TSNPs is achieved by controlling reaction kinetics and seed volume in a modified seed-mediated approach. The computed extinction spectra of TSNP, using the finite-difference time-domain (FDTD) method, are in excellent agreement with the experimental results, therefore assisting further in the investigation of the plasmonic properties of TSNP. The higher electric field enhancement offered by TSNP is systematically investigated by performing the FDTD simulations for various sizes and corner rounding of TSNP. The FDTD results show that the dipolar plasmon resonance wavelength, size, and corner rounding of TSNP are the principal contributing factors for designing the high-performance SERS substrate. Herein, we have used a portable Raman system for the SERS-based detection of three important explosive molecules: picric acid (PA), ammonium nitrate (AN), and 2, 4-dinitrotoluene (DNT). The TSNP-based SERS substrates display excellent intensity enhancement factors of?~?107 for rhodamine 6G (R6G) and PA and?~?105 for AN. The high sensitivity of SERS substrate with limit-of-detection (LOD) of value 2.3?×?10?11 M for PA and 3.1?×?10?8 M for AN and effective batch-to-batch reproducibility for DNT, thus offering its potentials for field detection of explosive molecules at trace-level.
Localized surface plasmon resonance (LSPR) properties of Au-Ag-Au three-layered nanoshell are investigated theoretically using the quasi-static electricity. Triple-bands LSPRs have been observed in the absorption spectrum. Both the peak wavelength and intensity could be fine tuned by altering the thickness and radius of the separate Ag layer. The properties and physical origin of the LSPR in the Au-Ag-Au three-layered nanoshell is much different from that of Au-dielectric-Au three-layered nanoshell. The corresponding physical mechanism has been illustrated by plotting the local electric field patterns and analyzing the interaction of the surface charges from different metal interfaces. Although the LSPR of Au-Ag-Au three-layered nanoshell is affected by the plasmon hybridization from all metal surfaces, it has been found that the plasmon coupling in different metallic layer takes main effect on the LSPR properties of different absorption peaks. These results indicate that the different type of metallic layers appearing alternately in the multilayered nanoshells could create abundant tunable LSPR modes, which provides potential for multiplex biosensing based on LSPR. 相似文献
Plasmonic nanoparticles are of great importance owing to their highly responsive ‘localized surface plasmon resonance’ (LSPR) behaviour to self-agglomeration/aggregation leading to the development of various nanosensors. Herein, we demonstrated the definite self-assembly of citrate functionalized silver nanoparticles (AgNPs) into a one-dimensional linear chain in presence of charged lead ions (Pb2+), one of the most toxic heavy metal pollutants. We have explored detail mechanism using a variety of spectroscopic tools and electron microscopy. The self-aggregation of AgNPs leads to the generation of new LSPR modes due to coupling of nearby existing modes. The conclusion of our experimental findings is duly supported by our developed numerical modelling based on the quasi-static approximation that the generated new LSPR modes are solely due to formation of chain-like aggregation of AgNPs. We have also monitored the LSPR spectra in the presence of other metal ions; however, only Pb2+ found to give such unique self-assembled geometry may due to its high interaction affinity with citrate. These findings play a key role for citrate functionalised AgNPs to be used as a low cost highly selective and sensitive lead ion sensor for potential application in industrial lead pollution monitoring. We have further varied several sensor parameters such as AgNPs size, concentration, and the allowed reaction time for it to be practically implemented as an efficient lead sensor meeting the Environmental Protection Agency recommendations.
Graphical abstract
The possible sensing mechanism of citrate-functionalized silver nanoparticles towards Pb2?+?followed by unique chain-like aggregation for potential atmospheric and industrial lead pollution monitoring.
The novel cellular-like gold nanofeet (CGNF) with movable gold core, which are derived from gold/silver core shell nanorods, have been generated by galvanic reaction protocol at room temperature. The optical property based on localized surface plasmon resonance (LSPR) has been evaluated in comparison with solid gold nanofeet, suggesting that obviously high LSPR sensitivity of CGNF contributes to enhancing optical effect for detection of analytes. In contrast with superquenching properties of nanogold for fluorescence detection of pollutants, highly sensitive detection of heavy metal contaminations, e.g., mercury ions, have been implemented via DNA functionalized silica-coated CGNF on the basis of surface enhanced fluorescence (SEF) approach. 相似文献
The synthesis of metal nano materials with controllable geometry has received extensive attention of researchers from the past decade. In this study, we report an unexplored new route for rapid and facile biogenic synthesis of silver nanocubes (AgNCs) by systematic reduction of silver ions with crude clove (Syzygium aromaticum) extract at room temperature. The formation and plasmonic properties of AgNCs were observed and the UV–vis spectra show characteristic absorption peak of AgNCs with broaden region at 430 nm along with the intense (124), (686), (454) and (235) peak in X-ray diffraction pattern confirmed the formation and crystallinity of AgNCs. The average size of AgNC cubes were found to be in the range of ~80 to 150 nm and it was confirmed by particles size distribution, scanning and transmission electron microscopy with elemental detection by EDAX. Further FTIR spectra provide the various functional groups present in the S. aromaticum extract which are supposed to be responsible and participating in the reaction for the synthesis of AgNCs. The AgNCs casted over glass substrate show an electrical conductivity of ~0.55 × 106 S/m demonstrating AgNCs to be a potential next generation conducting material due to its high conductivity. This work provides a novel and effective approach to control the shape of silver nanomaterial for impending applications. The current synthesis mode is eco-friendly, low cost and promises different potential applications such as biosensing, nanoelectronics, etc. 相似文献