Colorimetric determination of copper ions based on the catalytic leaching of silver from the shell of silver-coated gold nanorods

We have developed a method for the colorimetric determination of copper ions (Cu2+) that is based on the use of silver-coated gold nanorods (Au@Ag NRs). Its outstanding selectivity and sensitivity result from the catalytic leaching process that occurs between Cu2+, thiosulfate (S2O3 (2-)), and the surface of the Au@Ag NRs. The intrinsic color of the Au@Ag NRs changes from bright red to bluish green with decreasing thickness of the silver coating. The addition of Cu2+ accelerates the leaching of silver from the shell caused in the presence of S2O3 (2-). This result in a decrease in the thickness of the silver shell which is accompanied a change in color and absorption spectra of the colloidal solution. The shifts in the absorption maxima are linearly related to the concentrations of Cu2+ over the 3-1,000 nM concentration range (R = 0.996). The method is cost effective and was applied to the determination of Cu2+ in real water samples.We have developed a method for the colorimetric determination of copper ions (Cu2+) that is based on the use of silver-coated gold nanorods (Au@Ag NRs). Its outstanding selectivity and sensitivity result from the catalytic leaching process that occurs between Cu2+, thiosulfate (S2O3 (2-)), and the surface of the Au@Ag NRs. The intrinsic color of the Au@Ag NRs changes from bright red to bluish green with decreasing thickness of the silver coating. The addition of Cu2+ accelerates the leaching of silver from the shell caused in the presence of S2O3 (2-). This result in a decrease in the thickness of the silver shell which is accompanied a change in color and absorption spectra of the colloidal solution. The shifts in the absorption maxima are linearly related to the concentrations of Cu2+ over the 3-1,000 nM concentration range (R = 0.996). The method is cost effective and was applied to the determination of Cu2+ in real water samples

SERS Tags: Novel Optical Nanoprobes for Bioanalysis

CONTENTS1. Introduction1.1. Fundamental Theory of Surface-Enhanced Raman Scattering1.2. Optical Properties of SERS Tags2. Synthesis of SERS Tags2.1. Noble Metal Nanosubstrates2.1.1. Single Particle-Based SERS Substrates2.1.2. Nanoparticle Cluster-Based Substrates2.2. Raman Reporter Molecules2.2.1. Selection Principles and Reporter Types2.2.2. Self-Assembled Monolayer Coverage Strategy2.3. Surface Coating for Protection2.3.1. Biomolecule Coating2.3.2. Polymer Coating2.3.3. Liposome Coating2.3.4. Silica Coating2.4. Attachment of Targeting Molecules3. Bioanalysis Applications3.1. Ionic and Molecular Detection3.2. Pathogen Detection3.3. Live-Cell Imaging3.3.1. Cancer Marker Detection3.3.2. Intercellular Microenvironment Sensing3.4. Tissue SERS Imaging3.5. In Vivo SERS Imaging4. Challenges and Perspectives4.1. Reproducible Signal of SERS Tags4.1.1. Precisely Controlled Hot Spots for Nanosubstrates4.1.2. Calibration of SERS Intensities and Enhancements4.2. Improving Multiplexing Capability4.3. Reduced Size for Subcellular Imaging4.4. Development of Multifunctional Nanoplatforms4.4.1. Magnetic SERS Dots4.4.2. Multimodal Imaging Dots4.4.3. SERS Tag-Based Therapeutic Systems4.5. Biocompatibility5. Conclusions and Remarks</ul

Application of the light-front holographic wavefunction for heavy-light pseudoscalar meson in Bd,s→Dd,sPB_{d,s}\to D_{d,s}P decays

In this paper we extend our analyses of the decay constant and distribution amplitude with an improved holographic wavefunction to the heavy-light pseudoscalar mesons. In the evaluations, the helicity-dependence of the holographic wavefunction is considered; and an independent mass scale parameter is employed to moderate the strong suppression induced by the heavy quark. Under the constraints from decay constants and masses of pseudoscalar mesons, the $\chi^2$-analyses for the holographic parameters exhibit a rough consistence with the results obtained by fitting the Regge trajectory. With the fitted parameters, the results for the decay constants and distribution amplitudes are presented. We then show their application in evaluating the $B_{d,s}\to D_{d,s}P$ decays, in which the power-suppressed spectator scattering and weak annihilation corrections are first estimated. Numerically, the spectator scattering and weak annihilation corrections present a negative shift of about $0.7\%$ on the branching fractions; while, the predictions are still larger than the experimental data. Such small negative shift confirms the estimation based on the power counting rules.Comment: 10 pages, 5 figure

Highly Sensitive Surface-Enhanced Raman Scattering Sensing of Heparin Based on Antiaggregation of Functionalized Silver Nanoparticles

We report a simple and sensitive surface-enhanced Raman scattering (SERS) platform for the detection of heparin, based on antiaggregation of 4-mercaptopyridine (4-MPY) functionalized silver nanoparticles (Ag NPs). Here, protamine was employed as a medium for inducing the aggregation of negatively charged 4-MPY functionalized Ag NPs through surface electrostatic interaction, which resulted in significantly enhanced Raman signal of the Raman reporter. However, in the presence of heparin, the interaction between heparin and protamine decreased the concentration of free protamine, which dissipated the aggregated 4-MPY functionalized Ag NPs and thus decreased Raman enhancement effect. The degree of aggregation and Raman enhancement effect was proportional to the concentration of added heparin. Under optimized assay conditions, good linear relationship was obtained over the range of 0.5-150 ng/mL (R-2 = 0.998) with a minimum detectable concentration of 0.5 ng/mL in standard aqueous solution. Furthermore, the developed method was also successfully applied for detecting heparin in fetal bovine serum samples with a linear range of 1-400 ng/mL.We report a simple and sensitive surface-enhanced Raman scattering (SERS) platform for the detection of heparin, based on antiaggregation of 4-mercaptopyridine (4-MPY) functionalized silver nanoparticles (Ag NPs). Here, protamine was employed as a medium for inducing the aggregation of negatively charged 4-MPY functionalized Ag NPs through surface electrostatic interaction, which resulted in significantly enhanced Raman signal of the Raman reporter. However, in the presence of heparin, the interaction between heparin and protamine decreased the concentration of free protamine, which dissipated the aggregated 4-MPY functionalized Ag NPs and thus decreased Raman enhancement effect. The degree of aggregation and Raman enhancement effect was proportional to the concentration of added heparin. Under optimized assay conditions, good linear relationship was obtained over the range of 0.5-150 ng/mL (R-2 = 0.998) with a minimum detectable concentration of 0.5 ng/mL in standard aqueous solution. Furthermore, the developed method was also successfully applied for detecting heparin in fetal bovine serum samples with a linear range of 1-400 ng/mL

Highly sensitive label-free colorimetric sensing of nitrite based on etching of gold nanorods

A simple colorimetric method with high sensitivity and selectivity was developed for sensing of nitrite as low as 4.0 mu M by naked eyes, which is based on etching of gold nanorods accompanied by shape changes in aspect ratios (length/width) and a visible color change from bluish green to red and then to colorless with the increase of nitrite

Neuroendocrine markers insulinoma-associated protein 1, chromogranin, synaptophysin, and CD56 show rare positivity in adenocarcinoma ex-goblet cell carcinoids

Background: Adenocarcinoma ex-goblet cell carcinoid (AdexGCC) was considered a neuroendocrine adenocarcinoma, despite majority of tumor cells being negative for conventional neuroendocrine markers such as chromogranin and synaptophysin. Recently, insulinoma-associated protein 1 (INSM1) has been identified as a novel neuroendocrine marker that is more sensitive than chromogranin, synaptophysin, and CD56 in pulmonary neuroendocrine tumors. Methods: We studied this marker in conjunction with chromogranin, synaptophysin, and CD56 in 36 appendiceal AdexGCCs (21 primaries, 15 metastatic). Results: Primary AdexGCCs showed staining for INSM1, chromogranin, synaptophysin, and CD56 in 13/21 (62%), 18/21 (86%), 18/21 (86%), and 9/19 (47%) cases, respectively. However, the mean proportion of tumor cells stained for INSM1, chromogranin, synaptophysin, and CD56 was only 8.0% (median 1%, range 0-70%), 15.7% (median 2%, range 0-70%), 19.9% (median 5%, range 0-90%), and 5.6% (median 0%, range 0-50%), respectively. Metastatic AdexGCCs showed staining for INSM1, chromogranin, synaptophysin, and CD56 in 8/15 (53%), 11/15 (73%), 12/15 (80%), and 3/14 (21%) cases. The mean proportion of tumor cells stained for INSM1, chromogranin, synaptophysin, and CD56 in metastatic tumors was 1% (median 1%, range 0-3%), 12% (median 1%, range 0-85%), 17% (median 5%, range 0-85%), and 2% (median 0%, range 0-20%), respectively. Conclusions: Primary and metastatic AdexGCCs showed no difference in INSM1, chromogranin, synaptophysin, or CD56 staining. INSM1 exhibits low expression in AdexGCCs and is expressed by a lower proportion of tumor cells compared to chromogranin and synaptophysin

A fast and low-cost spray method for prototyping and depositing surface-enhanced Raman scattering arrays on microfluidic paper based device

In this study, a fast, low-cost, and facile spray method was proposed. This method deposits highly sensitive surface-enhanced Raman scattering (SERS) silver nanoparticles (AgNPs) on the paper-microfluidic scheme. The procedures for substrate preparation were studied including different strategies to synthesize AgNPs and the optimization of spray cycles. In addition, the morphologies of the different kinds of paper substrates were characterized by SEM and investigated by their SERS signals. The established method was found to be favorable for obtaining good sensitivity and reproducible results. The RSDs of Raman intensity of randomly analyzing 20 spots on the same paper or different filter papers depositing AgNPs are both below 15%. The SERS enhancement factor is approximately 2 x 10(7). The whole fabrication is very rapid, robust, and does not require specific instruments. Furthermore, the total cost for 1000 pieces of chip is less than $20. These advantages demonstrated the potential for growing SERS applications in the area of environmental monitoring, food safety, and bioanalysis in the future

Colorimetric sensing of copper(II) based on catalytic etching of gold nanoparticles

Based on the catalytic etching of gold nanoparticles (AuNPs), a label-free colorimetric probe was developed for the detection of Cu2+ in aqueous solutions. AuNPs were first stabilized by hexadecyltrimethylammonium bromide in NH3-NH4Cl (0.6 M/0.1 M) solutions. Then thiosulfate (S2O32-) ions were introduced and AuNPs were gradually dissolved by dissolved oxygen. With the further addition of Cu2+, Cu(NH3)(4)(2+) oxidized AuNPs to produce Au(S2O3)(2)(3-) and Cu(S2O3)(3)(5-), while the later was oxidized to Cu(NH3)(4)(2+) again by dissolved oxygen. The dissolving rate of AuNPs was thereby remarkably promoted and Cu2+ acted as the catalyst. The process went on due to the sufficient supply of dissolved oxygen and AuNPs were rapidly etched. Meanwhile, a visible color change from red to colorless was observed. Subsequent tests confirmed such a non-aggregation-based method as a sensitive (LOD= 5.0 nM or 032 ppb) and selective (at least 100-fold over other metal ions except for Pb2+ and Mn2+) way for the detection of Cu2+ (linear range, 10-80 nM). Moreover, our results show that the color change induced by 40 nM Cu2+ can be easily observed by naked eyes, which is particularly applicable to fast on-site investigations. (C) 2013 Elsevier B.V. All rights reserved.Based on the catalytic etching of gold nanoparticles (AuNPs), a label-free colorimetric probe was developed for the detection of Cu2+ in aqueous solutions. AuNPs were first stabilized by hexadecyltrimethylammonium bromide in NH3-NH4Cl (0.6 M/0.1 M) solutions. Then thiosulfate (S2O32-) ions were introduced and AuNPs were gradually dissolved by dissolved oxygen. With the further addition of Cu2+, Cu(NH3)(4)(2+) oxidized AuNPs to produce Au(S2O3)(2)(3-) and Cu(S2O3)(3)(5-), while the later was oxidized to Cu(NH3)(4)(2+) again by dissolved oxygen. The dissolving rate of AuNPs was thereby remarkably promoted and Cu2+ acted as the catalyst. The process went on due to the sufficient supply of dissolved oxygen and AuNPs were rapidly etched. Meanwhile, a visible color change from red to colorless was observed. Subsequent tests confirmed such a non-aggregation-based method as a sensitive (LOD= 5.0 nM or 032 ppb) and selective (at least 100-fold over other metal ions except for Pb2+ and Mn2+) way for the detection of Cu2+ (linear range, 10-80 nM). Moreover, our results show that the color change induced by 40 nM Cu2+ can be easily observed by naked eyes, which is particularly applicable to fast on-site investigations. (C) 2013 Elsevier B.V. All rights reserved

Fluorescent sensing of mercury(II) based on formation of catalytic gold nanoparticles

A fluorescence assay for the highly sensitive and selective detection of Hg2+ using a gold nanoparticle (AuNP)-based probewas proposed. The assay was based on the formation of Hg-Au alloys, which accelerated the oxidization of o-phenylenediamine by dissolved oxygen to produce 2,3-diaminophenazine, a fluorescent product.;A fluorescence assay for the highly sensitive and selective detection of Hg2+ using a gold nanoparticle (AuNP)-based probewas proposed. The assay was based on the formation of Hg-Au alloys, which accelerated the oxidization of o-phenylenediamine by dissolved oxygen to produce 2,3-diaminophenazine, a fluorescent product

Label free colorimetric sensing of thiocyanate based on inducing aggregation of Tween 20-stabilized gold nanoparticles

Based on inducing the aggregation of gold nanoparticles (AuNPs), a simple colorimetric method with high sensitivity and selectivity was developed for the sensing of thiocyanate (SCN-) in aqueous solutions. Citrate-capped AuNPs were prepared following a classic method and Tween 20 was subsequently added as a stabilizer. With the addition of SCN-, citrate ions on AuNPs surfaces were replaced due to the high affinity between SCN- and Au. As a result, Tween 20 molecules adsorbed on the AuNPs surfaces were separated and the AuNPs aggregated. The process was accompanied by a visible color change from red to blue within 5 min. The sensing of SCN- can therefore be easily achieved by a UV-vis spectrophotometer or even by the naked eye. The potential effects of relevant experimental conditions, including concentration of Tween 20, pH, incubation temperature and time, were evaluated to optimize the method. Under optimized conditions, this method yields excellent sensitivity (LOD = 0.2 mu M or 11.6 ppb) and selectivity toward SCN-. Our attempt may provide a cost-effective, rapid and simple solution to the inspection of SCN- ions in saliva and environmental aqueous samples