Seed-mediated Synthesis Method Research Articles

Au@Ag nanostructures for the sensitive detection of hydrogen peroxide

Hydrogen peroxide (H2O2) is an important molecule in biological and environmental systems. In living systems, H2O2 plays essential functions in physical signaling pathways, cell growth, differentiation, and proliferation. Plasmonic nanostructures have attracted significant research attention in the fields of catalysis, imaging, and sensing applications because of their unique properties. Owing to the difference in the reduction potential, silver nanostructures have been proposed for the detection of H2O2. In this work, we demonstrate the Au@Ag nanocubes for the label- and enzyme-free detection of H2O2. Seed-mediated synthesis method was employed to realize the Au@Ag nanocubes with high uniformity. The Au@Ag nanocubes were demonstrated to exhibit the ability to monitor the H2O2 at concentration levels lower than 200 µM with r2 = 0.904 of the calibration curve and the limit of detection (LOD) of 1.11 µM. In the relatively narrow range of the H2O2 at concentration levels lower than 40 µM, the LOD was calculated to be 0.60 µM with r2 = 0.941 of the calibration curve of the H2O2 sensor. This facile fabrication strategy of the Au@Ag nanocubes would provide inspiring insights for the label- and enzyme-free detection of H2O2.

Refractive index sensitivity of Au nanostructures in solution and on the substrate

In this work, we present the synthesis and surface immobilization of Au nanostars, Au nanocubes and Au nanorods for localized surface plasmon resonance (LSPR)-based refractometric sensing applications. Au nanostructures exhibiting LSPR peak positions in 500–900 nm spectral range were prepared by seed-mediated synthesis method. The refractive index (RI) sensitivity of all these nanostructures in the colloidal solution were measured and the sample exhibiting highest sensitivity in each category were immobilized on the glass substrate. The surface immobilized nanostructures were investigated for RI sensing. Au nanostars having LSPR peak position at 767 nm exhibited highest RI sensitivity of 484 nm/RIU in solution and 318 nm/RIU on the substrate. This study gives an outline for selecting the Au nanostructures for developing plasmonic sensing platforms.

Gold nanoparticles enhanced fluorescence for highly sensitive biosensors based on localized surface plasmon resonance applied in determination C-reactive protein

Introduction: C-reactive protein (CPR) is known as an inflammation marker related to numerous pathology. Optical biosensor based on the fluorescence dyed is widely used in diagnosis. There are still limitations on the fluorescence signal detection due to the photobleaching effect. The localized surface plasmon resonance (LSPR) performed by gold nanoparticles (Au NPs) is testified for the enhancement of photo-signal gathered from the dye molecules.
 Methods: In this study, Au NPs were used for their significant optical properties and biocompatibility additionally. The seed-mediated synthesis method provided stable NPs with all the essential qualities. A series of modification steps were done on a glass substrate before the bio-bonding for fluorescence-based sensing by a transmission mode (T-mode) detection system which is introduced for the first time in Viet Nam.
 Results: The synthetic Au NPs in nanosphere structure evinced the absorbance at a maximum wavelength is 521 nm. All the followed alterations showed the accomplishment in forming the in need linking proved through the basic analysis methods. Finally, CRP with the Alexa 488 dye was observed for average at 4.8 folds of enhancement factor compared between the Au NPs coating and non-coating substrate detected by the T-mode system. The low coefficient of variation at under 0.7% appeared for the repeatability and stability of this sensor.
 Conclusion: The completely modern approach of the T-mode system combined with the LSPR applied in fluorescence sensors enhanced is developed successfully. Also, the future prospect of this designed sensing method is promising by changing the materials' structures and ingredients.
 Keywords: LSPR, gold nanoparticles, fluorescence enhancement, C-reaction protein, optical biosensors