Nanoplasmonic Sensing using Metal Nanoparticles

Abstract

In our modern society, we are surrounded by numerous sensors, constantly feeding us information about our physical environment. From small, wearable sensors that monitor our physiological status to large satellites orbiting around the earth, detecting global changes. Although, the performance of these sensors have been significantly improved during the last decades there is still a demand for faster and more reliable sensing systems with improved sensitivity and selectivity. The rapid progress in nanofabrication techniques has made a profound impact for the development of small, novel sensors that enables miniaturization and integration. A specific area where nanostructures are especially attractive is biochemical sensing, where the exceptional properties of nanomaterials can be utilized in order to detect and analyze biomolecular interactions.The focus of this thesis is to investigate plasmonic nanoparticles composed of gold or silver and optimize their performance as signal transducers in optical biosensors. Metal nanoparticles exhibit unique optical properties due to excitation of localized surface plasmons, which makes them highly sensitive probes for detecting small, local changes in their surrounding environment, for instance the binding of a biomolecule to the nanoparticle surface. This is the basic principle behind nanoplasmonic sensing based on refractometric detection, a sensing scheme that offers real-time and label-free detection of molecular interactions.This thesis shows that the sensitivity for detecting local refractive index changes is highly dependent on the geometry of the metal nanoparticles, their interaction with neighboring particles and their chemical composition and functionalization. An increased knowledge about how these parameters affects the sensitivity is essential when developing nanoplasmonic sensing devices with high performance based on metal nanoparticles. VI VII Populärvetenskaplig sammanfattningI dagens samhälle finns en påtaglig vilja och strävan efter att kunna mäta, övervaka, analysera och reglera vardagliga funktioner och beteenden. Detta har lett till en explosionsartad utveckling av nya, funktionella sensorer som numera finns överallt i våra liv -i hemmet, på arbetsplatsen, i våra fickor och till och med inuti våra kroppar. En biosensor är en särskild typ av sensor som används för att detektera specifika kemiska eller biologiska ämnen genom att omvandla förekomsten av dessa ämnen till en mätbar signal. Biosensorer kan användas inom flera olika områden som livsmedelindustri, processövervakning, kriminalteknologi samt inom medicinsk diagnostik. Ofta är dock koncentrationen av de eftersökta ämnena mycket låg vilket ställer stora krav på sensorernas känslighet och precision.I denna avhandling beskrivs hur nanopartiklar av guld och silver kan användas som signalomvandlare i optiska biosensorer. Metalliska nanopartiklar har unika optiska egenskaper vilket gör dem väldigt känsliga mot små förändringar i dess absoluta närhet. Sådana förändringar ger upphov till en färgf...

Effect of Ar Gas Pressure on LSPR Property of Au Nanoparticles: Comparison of Experimental and Theoretical Studies

“…However, as the size of nanoparticle increases, the distance between the charges (poles) increases [45] and the interaction between two poles decreases by the phase retardation [16]. Because of this retardation, the restoring force is reduced and the resonance energy decreases and thus, LSPR peak shifts to longer wavelengths (smaller resonant frequency) [4,46]. Also, because of the higher charge densities on the larger nanoparticle, the intensity of LSPR increases.…”

“…Also, because of the higher charge densities on the larger nanoparticle, the intensity of LSPR increases. When two nanoparticles are placed next to each other closer than a distance equal or smaller than 2.5 times of the particle diameter, interparticle near field coupling occurs [4,17,47]. Oppositely, the particle behaves as a single-particle dipole mode.…”

“…When a metal nanoparticle is exposed to electromagnetic radiation, its conduction electrons oscillate collectively through resonant interaction with an incident electromagnetic field. This phenomenon is called as localized surface plasmon resonance (LSPR) effect [ 2 , 3 , 4 , 5 ]. Nanostructured materials show interesting optical, electronic, magnetic, and catalytic properties [ 6 ], especially.…”

Hybrid Plasmonics for Energy Harvesting and Sensing of Radiation and Heat

“…[19,20,[22][23][24][25] Both SPPs and LSPRs in metallic structures are sensitive to small changes of the refractive index of the surroundings, which makes them a powerful tool for nanosensing. [6,24,26] The LSPR in subwavelength metallic nanostructures is the reason for their unique absorption and scattering optical properties. [28] One of the first attempts to utilize metallic nanoparticles dates back to several hundred years ago when the manufactures used them as means of coloration and decoration of glass objects.…”

Nano-copper enhanced flexible device for simultaneous measurement of human respiratory and electro-cardiac activities

“…In this study, we proposed a flexible device that can simultaneously measure ECG and respiration (including parameters of electro-cardio frequency, electro-cardio rhythm, and electro-cardio amplitude; respiratory frequency, respiratory stress, and respiratory rhythm). Nanoparticle modification and finite element analysis (FEA) were used to improve the performance of sensing elements and optimize the structure of devices [41][42][43][44][45]. The key improvement of the device is that the carbon fiber was modified with nano-copper.…”