A prism-based imaging system for simultaneously detecting four species of single-molecule (SM) fluorophores was developed. As for the detection method, four spectrally distinct species of BigDye fluorophores were bound to 50-nm-diameter gold nanoparticles (AuNPs) to form AuNP/BigDye complexes. Four species of complexes were randomly immobilized on different fused-silica slides. BigDyes were excited by an argon-ion-laser (excitation wavelengths: 488 and 514.5 nm) beam through total internal reflection on the slide surface. SM fluorescence emitted from a complex was spectrally dispersed through a prism to form an SM spot elongated in the spectral direction on a charge-coupled device. A scattered light spot generated by the AuNP of the same complex under 594-nm laser illumination was used as a wavelength reference, and the SM fluorescence spectrum was obtained from the pixel-intensity pattern of the elongated SM spot. Peak locations of fluorescence spectra of all the observed SM spots were obtained, and their histograms were distinctly separated according to species. SM spots can thus be classified as one of four species according to their peak locations. By statistically analyzing the histograms, the classification accuracy was estimated to be above 93.8 %. The number of pixels in the spectral direction required for classifying four species of SM fluorophores was estimated to be 10. As for the conventional system (which uses two excitation lasers), 15 pixels are required. Using BigDyes as the four fluorophores (which consist of donors linked to acceptors and can be excited by just an argon-ion laser) is the reason that such a small number of pixels was achieved. The developed system can thus detect 1.5 times more SM fluorophores per field of view; that is, its throughput is 1.5 times higher. The approach taken in this study, namely, using BigDye with a prism-type system, is effective for increasing the throughput of DNA microarray-chip analysis and SM real-time DNA sequencing. 相似文献
The ferrihydrite mineral core of ferritin is a semi-conductor capable of catalyzing oxidation/reduction reactions. This report
shows that ferritin can photoreduce AuCl4− to form gold nanoparticles (AuNPs). An important goal was to identify innocent reaction conditions that prevented formation
of AuNPs unless the sample was illuminated in the presence of ferritin. TRIS buffer satisfied this requirement and produced
AuNPs with spherical morphology with diameters of 5.7 ± 1.6 nm and a surface plasmon resonance (SPR) peak at 530 nm. Size-exclusion
chromatography of the AuNP–ferritin reaction mixture produced two fractions containing both ferritin and AuNPs. TEM analysis
of the fraction close to where native ferritin normally elutes showed that AuNPs form inside ferritin. The other peak eluted
at a volume indicating a particle size much larger than ferritin. TEM analysis revealed AuNPs adjacent to ferritin molecules
suggesting that a dimeric ferritin–AuNP species forms. We propose that the ferritin protein shell acts as a nucleation site
for AuNP formation leading to the AuNP-ferritin dimeric species. Ferrihydrite nanoparticles (~10 nm diameter) were unable
to produce soluble AuNPs under identical conditions unless apo ferritin was present indicating that the ferritin protein shell
was essential for stabilizing AuNPs in aqueous solution. 相似文献
We report on the use of poly(allylamine) hydrochloride (PAH) as a reducing agent for the controlled formation of gold nanoparticles
(AuNPs) in the size range of 5–50 nm. The formation of AuNPs using this polymer matrix allows for the AuNPs to be imbedded
in the polymer matrix, once formed. The kinetics of AuNP formation are shown to be pseudo first-order in [HAuCl4] at room temperature. The kinetics of AuNP formation are controlled by the ratio of reducing agent to HAuCl4 as well as the overall concentration of the PAH and HAuCl4. Additionally, at low PAH:HAuCl4 mole ratios, the plasmon resonance wavelength can be controlled through the ratio of the reactants. This plamson resonance
shift is shown to be related to AuNP size by means of TEM imaging data on the AuNPs. 相似文献
A direct and simple inductively coupled plasma mass spectroscopy (ICP-MS) method for the determination of gold nanoparticles
(AuNP) with different particle sizes ranging from 5 to 20 nm and suspended in aqueous solutions is described. The results
show no significant difference compared to the determination of the same AuNPs after digestion, as claimed by the literature.
The obtained limit of quantification of the method is 0.15 μg/L Au(III) that corresponds to 4.40 × 109 AuNP/L, considering spherical AuNPs 15 nm sized. Spike recovery experiments have shown that the sample matrix is a significant
factor influencing the accuracy of the measurement. Spike recoveries from 93% to 95% are found for AuNP samples prepared in
trisodium citrate, while for deionized H2O a spike recovery of around 80% was obtained. The sample preparation mode along with the ICP-MS parameters have been optimized
and found to be crucial so as to achieve the required accuracy for the direct quantification of AuNP suspensions. The effect
of the nanoparticle size upon the ICP-MS signal also was studied, and only significant differences due to the chemical environment
and not to the AuNPs size were found. 相似文献
The emission spectra of the lanthanide chelates enable them to act as a donor for several acceptors emitting at different
wavelengths. Fluorescence resonance energy transfer between terbium(III) chelate labeled antibody Fab fragment (donor) and
a 17β-estradiol conjugated to Alexa Fluor 488, 555, 594 or 680 (acceptor) was employed to study the functionality of the terbium(III)
chelate as an efficient donor for several acceptors emitting from green to far-red. During measurement, the sensitized emission
of the acceptor was measured at acceptor specific wavelength. All the tested dyes proved to be efficient acceptors, and they
were successfully used in the competitive homogeneous E2 assay. The highest signal to background ratio and the best assay
performance was obtained with Alexa Fluor 680, due to the very low donor emission background at the far-red area. In addition,
the sensitized emission of both Alexa Fluor 488 and 680 could be measured simultaneously without significant cross talk. 相似文献
Cyanazine residue poses a great threat to human health and its derivatives would remain in soils, natural waters, and other environmental domains for a long time. Herein, a simple, rapid, and ultra-sensitive analytical method for the determination of cyanazine (CZ) based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs) is first described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of GSH-capped CdTe QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNP–CdTe QD system was recovered upon addition of CZ. CZ can adsorb on to the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on CdTe QDs was weakened, and the fluorescence intensity of CdTe QDs was recovered accordingly. A good linear correlation for detection of CZ was exhibited from 0.05 to 9 μM, and the detection limit reached 0.1568 μM, which was much lower than the safety limit required by the USA, the UK, and China. In order to probe into the selectivity of AuNPs towards CZ over other pesticides, various frequently used pesticides were mixed with AuNPs. AuNP composite solution shows good selectivity towards CZ among other pesticides. This method was successfully carried out for the assessment of CZ in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost, and non-time-consuming compared with traditional methods. 相似文献
Highly orientated polycrystalline ZnO films were deposited on sapphire, silicon and quartz substrates at room temperature by r.f. magnetron sputtering. Different photoluminescence (PL) spectra were observed when excited with different wavelength light. A UV emission peak (356 nm) and a blue peak (446 nm) were generated for the films on sapphire, silicon and quartz substrates, and only the 446 nm blue emission appeared for the films on glass substrates when the wavelength of the excitation light was 270 nm. With increasing the wavelength of the excitation light up to 300 and 320 nm, the UV emission disappeared for films on various substrates and the wavelength of the PL peaks increased up to 488 and 516 nm, respectively. When the wavelength of the excitation light increased to 398 nm, the PL spectrum becomes a wide band that is consistent with three emission peaks. 相似文献
We report on the production and fluorescence of active channel waveguides in Cr:LiSrAlF6. We have produced ∼10 μm wide and 5 μm high channel waveguides by He+ ion implantation, lithographic patterning and subsequent Ar+ ion sputtering. Diode-pumped waveguides emitted 13 μW of fluorescence light with a spectrum ranging from 760 nm to 900 nm
at a pump power of 165 mW and a pump wavelength of 660 nm. The compact and cheap optical pump source is a main advantage of
this fluorescence material. This makes Cr:LiSrAlF6 channel waveguides a suitable candidate for a broadband fluorescence source in low-coherence interferometry and other applications
in the near-infrared wavelength range.
PACS 42.70.Hj; 42.79.Gn; 42.30.Wb 相似文献
Photoluminescence spectra of organic semiconductors based on mono-, bis-, and triphthalocyanine containing erbium as a complexing
agent have been obtained in the range of 1–1.8 μm. Comparison of the spectral characteristics has shown that erbium triphthalocyanine
has the highest photoluminescence quantum yield at a wavelength of 1.5 μm. To enhance this effect, composite materials based
on erbium triphthalocyanine and a silicon slot structure have been synthesized, in which an additional increase in the photoluminescence
signal near 1.14 μm has been observed. At the same time, no photoluminescence signal has been observed near the wavelength
of 1.5 μm. This can be explained by taking into account the interaction of the erbium triphthalocyanine molecules with the
adsorption centers of the silicon matrix. 相似文献
The photoluminescence (PL) characteristics of co-sputtered Ge–Si duplex nanocrystal films were examined under excitation by a 325-nm HeCd laser, combined with Raman and Fourier-transform infrared reflection spectra analysis. A broad visible PL spectrum from the as-deposited Ge–Si nanocrystal films was observed in the wavelength range 350–700 nm. Basically, the PL spectrum can be considered to consist of two distinct parts originating from different emission mechanisms: (i) the spectrum in the range 350–520 nm, consisting of characteristic double peaks at 410 and 440 nm with PL intensities decreasing after vacuum annealing, probably due to vacancy defects in Si nanocrystals; and (ii) the spectrum in the range 520–700 nm, consisting of a characteristic peak at 550 nm with a PL intensity not affected by vacuum annealing, probably due to Ge-related interfacial defects. No size dependence of PL peak energy expected from quantum confinement effects was observed in the wavelength range investigated. However, with an increase of crystal size, the PL peak intensity in the blue zone decreased. The PL intensity is found to be strongly affected by silicon concentration. A film heated in air has a different PL mechanism from the as-deposited and vacuum-annealed films. PACS 78.67.Bf; 81.05.Cy; 81.15.Cd 相似文献
The current investigation deciphers aggregation pattern of gold nanoparticles (AuNPs) and lipid-treated AuNPs when subjected to aqueous sodium chloride solution with increasing ionic strengths (100–400 nM). AuNPs were synthesized using 0.29 mM chloroauric acid and by varying the concentrations of trisodium citrate (AuNP1 1.55 mM, AuNP2 3.1 mM) and silver nitrate (AuNP3 5.3 μM, AuNP4 10.6 μM) with characteristic LSPR peaks in the range of 525–533 nm. TEM analysis revealed AuNPs to be predominantly faceted nanocrystals with the average size of AuNP1 to be 35?±?5 nm, AuNP2 15?±?5 nm, AuNP3 30?±?5 nm, and AuNP4 30?±?5 nm and the zeta-average for AuNPs were calculated to be 31.23, 63.80, 26.08, and 28 nm respectively. Induced aggregation was observed within 10 s in all synthesized AuNPs while lipid-treated AuNP2 (AuNP2-L) was found to withstand ionic interferences at all concentration levels. However, lipid-treated AuNPs synthesized using silver nitrate and 1.55 mM trisodium citrate (AuNP3, AuNP4) showed much lower stability. The zeta potential values of lipid-treated AuNPs (AuNP1-L-1x/200, ??17.93?±?1.02 mV; AuNP2-L-1x/200, ??21.63?±?0.70; AuNP3-L-1x/200, ??14.54?±?0.90; AuNP3-L-1x/200 ??13.77?±?0.83) justified these observations. To summarize, AuNP1 and AuNP2 treated with lipid mixture 1 equals or above 1x/200 or 1x/1000 respectively showed strong resistance against ionic interferences (up to 400 mM NaCl). Use of lipid mixture 1 for obtaining highly stable AuNPs also provided functional arms of various lengths which can be used for covalent coupling.
Au nanoparticle (AuNP) core particles coated with a poly(N‐isopropylacrylamide) (pNIPAm) shell (Au@pNIPAm) are synthesized by seed mediated free radical polymerization. Subsequently, a temperature–light‐responsive photonic device is fabricated by sandwiching the Au@pNIPAm particles between two thin layers of Au. The optical device exhibits visual color and characteristic multipeak reflectance spectra, where peak position is primarily determined by the distance between two Au layers. Dual responsivities of the photonic device are achieved by combining the photothermal effect of AuNPs core (localized surface plasmon resonance (LSPR) effect) and the temperature responsivity of the pNIPAm shell. That is, the pNIPAm shell collapses as the temperature is increased above pNIPAm's lower critical solution temperature, either by direct heat input or heat generated by AuNPs' LSPR effect. To investigate the effect of AuNPs distribution in the microgels on the devices' photothermal responsivity, the Au@pNIPAm microgel‐based etalon devices are compared with that fabricated by AuNP‐doped pNIPAm‐based microgels; in terms of response kinetics and optical spectrum homogeneity. The uniform Au@pNIPAm microgel‐based devices show a fast response and exhibit a comparatively homogeneous spectrum over the whole slide. These materials can potentially find use in drug delivery systems, active optics, and soft robotics. 相似文献
ZnO nanorods with 30 nm-diameter ultra-thin pinheads and ultra-thin nanobelts were successfully synthesized using a thiourea
solution to etch nanorods and nancombs, which were obtained by a conventional thermal evaporation method. The materials obtained
were investigated by field emission scanning electron microscopy and energy-dispersive X-ray fluorescence. The data shows
that hydrogen ions play an important role in synthesizing ZnO nanorods with ultra-thin pinheads and ultra-thin nanobelts.
Field emission plots indicated that the turn-on field was reduced from 2.10 V/μm to 1.55 V/μm after thiourea solution treatment
at a current density of 0.1 μA/cm2. Room-temperature photoluminescence spectra from ZnO nanostructures showed the PL spectrum peaks shifted towards short wavelengths
with a large enhancement of UV bands compared with those of ZnO nanorods and nanocombs.
PACS 75.55.Gs; 61.46.-w; 81.40.Wx; 78.55.-m; 78.60.Fi 相似文献
We studied the steady-state fluorescence spectra of solutions of FET (4′-(diethylamino)-3-hydroxyflavone) in acetonitrile
that were excited at different temperatures by quanta with different energies located in the range of the main absorption
band and in its long-wavelength wing. We found that, at room temperature, the emission intensity ratio of the bands of the
normal and tautomeric forms, which are located at 505 and 570 nm, respectively, depends on the excitation wavelength. In the
range of the main absorption band 300–360 nm, this ratio remains nearly the same, i.e., 1.45, while, upon excitation in the
range of the long-wavelength wing 360–380 nm of the main band, it decreases to 1.33 at a wavelength of 460 nm. In this same
range, a long-wavelength excitation effect that is unusual for liquid inviscid solvents at room temperature, i.e., a bathochromic
shift of the entire short-wavelength emission band by 11 nm, manifests itself. We propose to explain these dependences using
energy diagrams, which take into account the dependence of free energy on the orientational polarization of the polar solvent.
The observed effect of the long-wavelength shift of the fluorescence spectrum with increasing excitation wavelength is explained
in terms of the inhomogeneous broadening of electronic spectra of polar solutions, and it should be described using the scheme
of energy states that takes into account sublevels of orientational broadening due to orientational dipole-dipole interactions
of the fluorophore with nearest molecules of the polar solvent, as well as the relation between the fluorophore lifetime in
the excited state and the dielectric relaxation time of solvent molecules in the field of the fluorophore dipole. 相似文献
We report on the role of dye–nucleobase interactions on the photophysical properties of the indocarbocyanine Cy3. The fluorescence
efficiency and lifetime of Cy3 increase in the presence of all four nucleoside monophosphates. This behavior correlates with
an increase in the activation energy for photoisomerization and a ∼4 nm red shift in the fluorescence spectrum. Changes are
more dramatic for the purines (dAMP, dGMP) than the pyrimidines (dCMP, dTMP), and for the nonsulfonated cyanine (DiIC2(3)) than the sulfonated dye (Cy3–SE). These results are consistent with a model in which Cy3–nucleoside π–π interactions
decrease the efficiency of photoisomerization, increasing the efficiency of fluorescence.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献