Equilibrium Morphology of Plasmonic Au/Polystyrene Dimeric Nanoparticle

Growth of a metal on nanoparticles has been considered to be a useful synthetic tool in a wide variety of applications ranging from catalysis to nanomedicine. This technique can combine more than two functionalities into a single nanoparticle. Most of the methods for such growth rely on a trial-and-error approach to produce grown nanoparticles with the desired sizes and shapes, which is rather time consuming and difficult to reproduce. Here we systematically studied the equilibrium morphology of metal/dielectric dimeric nanoparticle. A computational model was developed by considering the diffusion and surface energy of a metal and the interface energy between the metal and a dielectric. As a proof-of-concept, the growth of Au on a dimeric nanoparticle consisting of Au and polystyrene (PS) was considered. The effects of the surface and interface energy, the concentration of Au ion over the course of the growth, and the size of PS on the shape (i.e., morphology) of the grown nanoparticle were examined. Interestingly, the effects of the surface and interface energy of Au on its coverage of PS are found to be relatively negligible compared to the other two factors. A diagram for the equilibrium morphology with respect to the concentration of Au ion and the size of PS is proposed, which is qualitatively consistent with the experiment

Self-Assembled Three-Dimensional Nanocrown Array

Although an ordered nanoplasmonic probe array will have a huge impact on light harvesting, selective frequency response (<i>i.e.</i>, nanoantenna), and quantitative molecular/cellular imaging, the realization of such an array is still limited by conventional techniques due to the serial processing or resolution limit by light diffraction. Here, we demonstrate a thermodynamically driven, self-assembled three-dimensional nanocrown array that consists of a core and six satellite gold nanoparticles (GNPs). Our ordered nanoprobe array is fabricated over a large area by thermal dewetting of thin gold film on hexagonally ordered porous anodic alumina (PAA). During thermal dewetting, the structural order of the PAA template dictates the periodic arrangement of gold nanoparticles, rendering the array of gold nanocrown. Because of its tunable size (<i>i.e.</i>, 50 nm core and 20 nm satellite GNPs), arrangement, and periodicity, the nanocrown array shows multiple optical resonance frequencies at visible wavelengths as well as angle-dependent optical properties

Interfacial Synthesis of Two-Dimensional Dendritic Platinum Nanoparticles Using Oleic Acid-in-Water Emulsion

Here we propose facile and scalable synthesis of two-dimensional (2D) dendritic platinum nanoparticle at room temperature by exploiting an oil-in-water emulsion. The interfacial synthesis selectively provides platinum nanoparticle with 2D structure in high yield by controlling key reactants such as the amount of oleic acid and the concentration of block copolymer. Electrocatalytic activity of 2D dendritic platinum nanoparticle for oxygen reduction and methanol oxidation reaction is also examined

Immiscible Oil–Water Interface: Dual Function of Electrokinetic Concentration of Charged Molecules and Optical Detection with Interfacially Trapped Gold Nanorods

In this paper, we report that an immiscible oil–water interface can achieve the dual function of electrokinetic molecular concentration without external electric fields and sensitive optical detection without a microscope. As a proof-of-concept, we have shown that the concentration of positively charged molecules at the oleic acid–water interface can be increased significantly simply by controlling the pH. Three-dimensional phase field simulation suggests that the concentration of positively charged rhodamine 6G can be increased by about 10-fold at the interface. Surface-enhanced Raman spectroscopy (SERS) is utilized for label-free detection by taking advantage of this molecular accumulation occurring at the interface, since gold nanorods can be spontaneously trapped at the interface via electrostatic interaction. SERS measurements suggest that the immiscible oleic acid–water interface allows the limit of detection to be improved by 1–3 orders of magnitude

Dynamic Changes in the Protein Localization in the Nuclear Environment in Pancreatic β‑Cell after Brief Glucose Stimulation

Characterization of molecular mechanisms underlying pancreatic β-cell function in relation to glucose-stimulated insulin secretion is incomplete, especially with respect to global response in the nuclear environment. We focus on the characterization of proteins in the nuclear environment of β-cells after brief, high glucose stimulation. We compared purified nuclei derived from β-cells stimulated with 17 mM glucose for 0, 2, and 5 min using quantitative proteomics, a time frame that most likely does not result in translation of new protein in the cell. Among the differentially regulated proteins, we identified 20 components of the nuclear organization processes, including nuclear pore organization, ribonucleoprotein complex, and pre-mRNA transcription. We found alteration of the nuclear pore complex, together with calcium/calmodulin-binding chaperones that facilitate protein and RNA import or export to/from the nucleus to the cytoplasm. Putative insulin mRNA transcription-associated factors were identified among the regulated proteins, and they were cross-validated by Western blotting and confocal immunofluorescence imaging. Collectively, our data suggest that protein translocation between the nucleus and the cytoplasm is an important process, highly involved in the initial molecular mechanism underlying glucose-stimulated insulin secretion in pancreatic β-cells

Dynamic Changes in the Protein Localization in the Nuclear Environment in Pancreatic β‑Cell after Brief Glucose Stimulation

Characterization of molecular mechanisms underlying pancreatic β-cell function in relation to glucose-stimulated insulin secretion is incomplete, especially with respect to global response in the nuclear environment. We focus on the characterization of proteins in the nuclear environment of β-cells after brief, high glucose stimulation. We compared purified nuclei derived from β-cells stimulated with 17 mM glucose for 0, 2, and 5 min using quantitative proteomics, a time frame that most likely does not result in translation of new protein in the cell. Among the differentially regulated proteins, we identified 20 components of the nuclear organization processes, including nuclear pore organization, ribonucleoprotein complex, and pre-mRNA transcription. We found alteration of the nuclear pore complex, together with calcium/calmodulin-binding chaperones that facilitate protein and RNA import or export to/from the nucleus to the cytoplasm. Putative insulin mRNA transcription-associated factors were identified among the regulated proteins, and they were cross-validated by Western blotting and confocal immunofluorescence imaging. Collectively, our data suggest that protein translocation between the nucleus and the cytoplasm is an important process, highly involved in the initial molecular mechanism underlying glucose-stimulated insulin secretion in pancreatic β-cells

Dynamic Changes in the Protein Localization in the Nuclear Environment in Pancreatic β‑Cell after Brief Glucose Stimulation

Characterization of molecular mechanisms underlying pancreatic β-cell function in relation to glucose-stimulated insulin secretion is incomplete, especially with respect to global response in the nuclear environment. We focus on the characterization of proteins in the nuclear environment of β-cells after brief, high glucose stimulation. We compared purified nuclei derived from β-cells stimulated with 17 mM glucose for 0, 2, and 5 min using quantitative proteomics, a time frame that most likely does not result in translation of new protein in the cell. Among the differentially regulated proteins, we identified 20 components of the nuclear organization processes, including nuclear pore organization, ribonucleoprotein complex, and pre-mRNA transcription. We found alteration of the nuclear pore complex, together with calcium/calmodulin-binding chaperones that facilitate protein and RNA import or export to/from the nucleus to the cytoplasm. Putative insulin mRNA transcription-associated factors were identified among the regulated proteins, and they were cross-validated by Western blotting and confocal immunofluorescence imaging. Collectively, our data suggest that protein translocation between the nucleus and the cytoplasm is an important process, highly involved in the initial molecular mechanism underlying glucose-stimulated insulin secretion in pancreatic β-cells

Standoff Mechanical Resonance Spectroscopy Based on Infrared-Sensitive Hydrogel Microcantilevers

This paper reports a highly sensitive and selective remote chemical sensing platform for surface-adsorbed trace chemicals by using infrared (IR)-sensitive hydrogel microcantilevers. Poly­(ethylene glycol) diacrylate (PEG-DA) hydrogel microcantilevers are fabricated by ultraviolet (UV) curing of PEG-DA prepolymer introduced into a poly­(dimethylsiloxane) mold. The resonance frequency of a PEG-DA microcantilever exhibits high thermal sensitivity due to IR irradiation/absorption. When a tunable IR laser beam is reflected off a surface coated with target chemical onto a PEG-DA microcantilever, the resonance frequency of the cantilever shifts in proportion to the chemical nature of the target molecules. Dynamic responses of the PEG-DA microcantilever can be obtained in a range of IR wavelengths using a tunable quantum cascade laser that can form the basis for the standoff mechanical resonance spectroscopy (SMRS). Using this SMRS technique, we have selectively detected three compounds, dimethyl methyl phosphonate (DMMP), cyclotrimethylene trinitramine (RDX), and pentaerythritol tetranitrate (PETN), located 4 m away from the PEG-DA microcantilever detector. The experimentally measured limit of detection for PETN trace using the PEG-DA microcantilever was 40 ng/cm². Overall, the PEG-DA microcantilever is a promising candidate for further exploration and optimization of standoff detection methods

On-Chip Colorimetric Detection of Cu²⁺ Ions via Density-Controlled Plasmonic Core–Satellites Nanoassembly

We report on an on-chip colorimetric method for the detection and analysis of Cu²⁺ ions via the targeted assembly of plasmonic silver nanoparticles (2.6 nm satellites) on density-controlled plasmonic gold nanoparticles (50 nm cores) on a glass substrate. Without any ligand modification of the nanoparticles, by directly using an intrinsic moiety (carboxylate ion, COO^–) surrounded with nanoparticles, the method showed a high selectivity for Cu²⁺, resulting in a nearly 2 times greater optical response compared to those of other metal ions via the targeted core–satellites assembly. By modulating the surface chemistry, it was possible to control the density of core gold nanoparticles on the surface, thus permitting easy tuning of the optical responses induced by plasmon coupling generated between each core–satellites nanostructure. Using chips with a controlled optimal core density, we observed the remarkable scattering color changes of the chips from green to yellow and finally to orange with the increase of Cu²⁺ concentration. The detection limits of the fabricated chips with controlled core densities (ca. 1821 and 3636 particles/100 μm²) are 10 nM and 10 pM, respectively, which are quite tunable and below the level of 20 μM (or 1.3 ppm) defined by the United States Environmental Protection Agency. The findings suggest that the method is a potentially promising protocol for detecting small molecules with target selectivity and the tunability of the detection limits by replacing with ligands and adjusting core densities

Core–Satellites Assembly of Silver Nanoparticles on a Single Gold Nanoparticle via Metal Ion-Mediated Complex

We report core–satellites (Au–Ag) coupled plasmonic nanoassemblies based on bottom-up, high-density assembly of molecular-scale silver nanoparticles on a single gold nanoparticle surface, and demonstrate direct observation and quantification of enhanced plasmon coupling (i.e., intensity amplification and apparent spectra shift) in a single particle level. We also explore metal ion sensing capability based on our coupled plasmonic core–satellites, which enabled at least 1000 times better detection limit as compared to that of a single plasmonic nanoparticle. Our results demonstrate and suggest substantial promise for the development of coupled plasmonic nanostructures for ultrasensitive detection of various biological and chemical analytes