Microchimica Acta - A new method is presented for the visual detection of dicyandiamide (DCD). Gold nanoparticles (AuNPs) capped with gallic acid (GA) were synthesized in a single step at room... 相似文献
This study describes the use of 11-mercaptoundecanoic acid-capped gold nanoparticles (MUA-AuNPs) for selective extraction of melamine prior to analysis by capillary electrophoresis with UV detection. The highest degree of melamine-induced aggregation of MUA-AuNPs was found to occur at pH 5.0, indicating that the NP aggregation is mainly because of hydrogen bonding between the carboxylate groups of MUA and the amine groups of melamine. Moreover, the degree of melamine-induced NP aggregation gradually increased when the chain length of the mercaptoalkanoic acid was increased from two to 12 carbon atoms. At pH 5.0, the extraction efficiency of melamine was highly dependent on the concentration of MUA-AuNPs, the concentration of dithiothreitol (DTT), the extraction time between MUA-AuNPs and melamine, and the incubation time between melamine-adsorbed AuNPs and DTT. The separation of the extracted melamine and DTT (releasing agent) was accomplished using a solution of 10 mM phosphate (pH 6.0) containing 1.6% (v/v) poly(diallyldimethylammonium chloride). Under the optimum extraction and separation conditions, the limit of detection at a signal-to-noise ratio of 3 was estimated to be 77 pM for melamine, with linear range of 1-1000 nM. The proposed method was successfully applied to the determination of melamine in tap water and in milk. 相似文献
This paper presents an efficient strategy for the specific immobilization of fully functional proteins onto the surface of nanoparticles. Thioctic acid-derivatized gold clusters are used as a scaffold for further stepwise modification, leading to a cobalt(II)-terminated ligand shell. A histidine tag introduced by genetic engineering into a protein is coordinated to this transition metal ion. The specific immobilization has been demonstrated for the cases of a genetically engineered horseradish peroxidase and ferredoxin-NADP(+) reductase, confirming the attachment of the fully functional proteins to the Co(II)-terminated nanointerface. The absence of nonspecific protein adsorption and the specificity of the binding site have been verified using several analogues of the enzymes without the histidine tag. 相似文献
This paper reports findings of an investigation of the unusual colorimetric change of gold nanoparticles in the presence of thiol-containing amino acids such as homocysteine, cysteine and glutathione. The colorimetric change for homocysteine exhibits a rate that is about two orders of magnitude higher than that for cysteine, and at least five orders of magnitude higher than that for glutathione. The reactivity is effectively reduced or suppressed by the coexistence of either cysteine or glutathione. It is believed that the reactivity involves encapsulation of the particles by the thiol-containing amino acids which is followed by crosslinking at the encapsulating shells. In comparison with cysteine and glutathione, homocysteine has a slower encapsulating rate but a faster crosslinking rate. Implications of the findings of the interfacial encapsulation and crosslinking reactivities of gold nanoparticles to potential nanoparticle-enhanced analytical detection of thiol-containing amino acids are also briefly discussed. 相似文献
The solubility of charged nanoparticles is critically dependent on pH. However, the concentration range available with bases such as NaOH is quite narrow, since the particles precipitate due to compression of the electric double layer when the ionic strength is increased. The stability of mercaptoundecanoic acid-capped Au nanoparticles is studied at a set pH using the hydroxide as base and different cations of various sizes. The counterions used are sodium (Na(+)), tetramethylammonium (TMA(+)), tetraethylammonium (TEA(+)), and tetrabutylammonium (TBA(+)). The particles precipitate in the 70-90 mM range with Na(+) as the counterion, but with quaternary ammonium hydroxides the particles are stable even in concentrations exceeding 1 M. The change in solubility is linked to a strongly adsorbed layer on the surface of the ligand shell of the nanoparticles. The increased concentration range obtained with TEAOH is further used to facilitate thiol exchange which occurs at a greater extent than would be achieved in NaOH solution. 相似文献
We have developed a new internal standard method for the determination of the concentration of captopril (CAP) through surface-assisted
laser desorption/ionization mass spectrometry (SALDI-MS) using gold nanoparticles (Au NPs). This approach provided linearity
for CAP over the concentration range 2. 5–25 μM (R2 = 0. 987), with a limit of detection (signal-to-noise ratio = 3) of 1. 0 μM. The spot-to-spot variations in the concentration of CAP through SALDI-MS analyses performed in the absence and presence
of the internal standard were 26% and 9%, respectively (15 measurements). This approach provides simplicity, accuracy, precision,
and great reproducibility to the determination of the levels of CAP in human urine samples. 相似文献
A novel DNA scaffold, called a DNA slit, was designed for the programmed positioning of Au nanoparticles (AuNPs), and various patterns of thiolated DNA slits were constructed. AuNPs were correctly placed at the predesigned positions in the thiolated DNA slits, indicating that the thiolated staples and the slit cavities guide the correct assembly of AuNPs. 相似文献
We have demonstrated that carboxylic acid-capped gold nanoparticles were self-assembled to form two-dimensional (2D) and/or three-dimensional (3D) superlattices at an air/water interface in the presence of a bifunctional hydrogen-bonding mediator such as 4-pyridinecarboxylic acid (PyC) or trans-3-(3-pyridyl)acrylic acid (PyA). Transmission electron microscopy revealed a hexagonal close-packed arrangement of nanoparticles in the superlattice with an extension of interparticle spacing. In the 2D superlattices, larger particles produced a higher-quality assembly having long-range translational ordering. Attenuated total reflectance IR (ATR-IR) spectroscopy revealed the presence of hydrogen bonds between the mediator used and the capping agents of carboxylic acid on nanoparticle surfaces. Since the experimentally obtained interparticle separation distance agreed approximately with that obtained by the geometrical model calculations, we conclude that the hydrogen-bonding mediation controlled the interparticle spacing or structure by monomolecular incorporation between adjacent nanoparticles in the superlattices. 相似文献
This study aims at developing a new eco-friendly process for the synthesis of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using purified URAK. URAK is a fibrinolytic enzyme produced by Bacillus cereus NK1. The enzyme was purified and used for the synthesis of AuNPs and AgNPs. The enzyme produced AgNPs when incubated with 1 mM AgNO3 for 24 h and AuNPs when incubated with 1 mM HAuCl4 for 60 h. But when NaOH was added, the synthesis was rapid and occurred within 5 min for AgNPs and 12 h for AuNPs. The synthesized nanoparticles were characterized by a peak at 440 nm and 550 nm in the UV-visible spectrum. TEM analysis showed that AgNPs of the size 60 nm and AuNPs of size 20 nm were synthesized. XRD confirmed the crystalline nature of the nanoparticles and AFM showed the morphology of the nanoparticle to be spherical. FT-IR showed that protein was responsible for the synthesis of the nanoparticles. This process is highly simple, versatile and produces AgNPs and AuNPs in environmental friendly manner. Moreover, the synthesized nanoparticles were found to contain immobilized enzyme. Also, URAK was tested on RAW 264.7 macrophage cell line and was found to be non-cytotoxic until 100 μg/ml. 相似文献
The authors describe a sensitive and rapid upconversion fluorescence based immunoassay for the neonicotinoid insecticide imidaclothiz (IMI). Upconversion nanoparticles (UCNPs) consisting of hexagonal phase NaYF4:Yb,Er were functionalized with amino groups and coupled to antibody against IMI. Gold nanoparticles (AuNPs) were used to label the antigen (analyte). Competitive binding of IMI and AuNPs-labeled IMI to the UCNPs-labeled antibody results in a change in the fluorescence of the UCNPs at excitation/emission wavelengths of 980/544 nm. Under optimal conditions, the concentration of IMI producing a 50% saturation of the signal (SC50) is 18.9 ng mL?1, and the limit of detection is 2.1 ng mL?1. The method was applied to the determination of IMI in (spiked) paddy water, soil, pear, rice, apple, tomato, pakchoi and cabbage. Average recoveries range from 67.4% to 104.6%, and relative standard deviations from 1.9% to 10.3%. The results correlate well with those obtained by HPLC, the relative correlation coefficient (R2) being 0.9811.
Graphical abstract Based on inner filter effect (IFE), a novel immunoassay for imidaclothiz (IMI) was developed by using upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs) as labels. Competitive binding of IMI and AuNPs-labeled IMI to the UCNPs-labeled antibody results in a change in the fluorescence of the UCNPs at excitation/emission wavelengths of 980/544 nm.
To achieve label-free detection of amino acids in capillary-based electrokinetic chromatography-thermal lens microscopy (EKC-TLM), gold nanoparticles (GNPs), which possess the absorption around 500nm attributed to surface plasmon resonance (SPR), were added to the background solution (BGS). Since the SPR absorption of the GNPs exhibits a sensitive response toward environmental changes and the degree of aggregation, the sensitive detection of non-absorbing species is expected by using the GNPs in EKC-TLM (GNP-EKC-TLM). In the GNP-EKC-TLM analysis of glutamic acid (Glu), a sharp peak was observed when the GNPs were added to the BGS. The plot of the peak area of Glu against its concentration gave a good linear relationship and the limit of detection was estimated to be 25mug/mL. Furthermore, a baseline separation of lysine and Glu was successfully achieved. Thus, the EKC separation and label-free TLM detection of the amino acids can be realized only by adding the GNPs into the BGSs. 相似文献
A chemiluminescent (CL) detection method has been developed for DNA hybridization. The assay relies on a sandwich-type DNA
hybridization in which gold nanoparticles modified with alkylthiol-capped oligonucleotide strands are used as probes to monitor
the presence of the specific target DNA. The , which is the dissolving product of the gold nanoparticles anchored on the DNA hybrids, serves as an analyte in the H2O2–luminol– CL reaction for the indirect measurement of the target DNA. The combination of the remarkable sensitivity of the CL analysis
with the large number of released from each DNA hybrid allows a detection limit at levels as low as 0.1 pM of the target DNA. Moreover, with a further
silver amplification step, the detection limit will be pushed down to the femtomolar domain.
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Gold nanoparticles were prepared via a simple photoreduction technique in the presence of transition metal monosubstituted
Keggin heteropolyanions (PW11M, M= Cu2+, Ni2+, Zn2+, Fe3+), in which PW11M acted as reducing agent, photocatalyst and stabilizer. The results indicated that the formation rate and
morphology of the nanoparticles strongly depended on the kind of transition metal substituted in heteropolyacid and the preparation
conditions, such as irradiation time and propan-2-ol amount. The photoreduction rates of PW11Zn and PW11Fe were faster than
those of PW11Ni and PW11Cu. The shapes of the nanoparticles synthesized in the presence of PW11Fe and PW11Zn were nearly uniform
spheres, whereas the morphologies of the nanoparticles synthesized in the presence of PW11Ni and PW11Cu were found to contain
a mixture of flat triangular/hexagonal structures as well as spheres. Increases in the irradiation time and the propan-2-ol
amount could make the morphology of nanoparticles uniform and shorten the formation time of the nanoparticles.
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Translated from Chinese Journal of Applied Chemistry, 2007, 24(7) (in Chinese) 相似文献
We report a new methodology for the size-controlled aqueous synthesis of gold nanoparticles using geminis with different spacers as ligands. Geminis possess a unique structure in which two hydrophobic chains and two polar headgroups are combined via a spacer. We herein demonstrate that the spacer can be used as a tool to control particle size when geminis are used as ligands for gold nanoparticles. Varying the spacer length of geminis yields facile control over the size and size distribution of nanoparticles. For the 18-s-18-capped gold nanoparticles, FTIR and TGA experiments indicate that the geminis form bilayers on the surface of gold nanoparticles, which serve as templates that control the formation of nanoparticles. The smallest particles are obtained with a moderate spacer length (s = 8) because in that case the gemini bilayers interdigitate to the fullest degree to reach the maximum chain-chain interaction, thus yielding the most compact coating on the surface of gold nanoparticles. This work provides a new approach to the size control of nanoparticles. 相似文献
Gold nanoparticles were self-assembled onto the surface of solubilized carbon nanotubes through an interlinker of bi-functionalized molecule (PHT) terminated with pyrenyl unit at one end and thiol group at the other end. While the fluorescence of PHT is quenched moderately by the carbon nanotubes, the fluorescence is almost totally quenched by the further binding of gold nanoparticles. The enhancement of the Raman responses of nanotubes by the gold nanoparticles is also observed. These results imply there are charge transfer interactions between nanotubes and gold nanoparticles. 相似文献
We report the synthesis of nitric oxide-releasing gold nanoparticles formed by place-exchange reaction of hexanethiol monolayer-protected clusters with diamine nitric oxide donor precursor molecules, which are subsequently converted to N-diazeniumdiolate NO donors. The nitric oxide release from the N-diazeniumdiolate-modified gold nanoparticles is tunable by varying the number and/or the chemical structure of the exchanged amine ligands. The size and stability of NO-releasing nanoparticles may prove useful for a range of biomedical and pharmaceutical applications. 相似文献
Gold nanoparticles with diameters of ca. 13 nm were synthesised by UV irradiation of a supramolecular organogel into which HAuCl4 and tetraoctylammonium bromide had been diffused-the gel network plays an essential role in nanoparticle stabilisation. 相似文献
The utilization of metal nanoparticles (NPs) to fabricate metal electrodes under mild conditions is one of the most studied topic in recent years. In this work, colloidal Au NPs were deposited on two isostructural molecular crystals, namely 1,2,3,4-tetrafluoro-7-thiomethyl-acridine (MeSAcr) and 1,2,3,4-tetrafluoro-7-methoxy-acridine (MeOAcr), exposing S atoms and O atoms, respectively, at their largest crystal faces. The depositions were carried out mainly by drop casting under ambient conditions, increasing the contact time from 1 to 120 min, and the samples were then analyzed by atomic force microscopy (AFM) to evaluate the coverage. Thanks to the affinity between S and Au atoms, Au NPs are observed to adhere on the MeSAcr surface within 1-min contact time, whereas at least 1h is required to find NPs on the MeOAcr surface. NP adsorption is also affected by the substrate surface morphology; indeed, step edges represent preferential adsorption sites even in the absence of Au-S interaction. Experiments under different conditions were performed to maximize the coverage on MeSAcr, reaching values up to 13%. AFM equipped with fluid cell was also employed to simultaneously depositing and imaging NPs, achieving a better understanding of the adsorption mechanism. 相似文献