Search results for "surface plasmon resonance"
showing 10 items of 208 documents
Plasmonic Silver Nanorod Sensitivity: Experiment and Simple Theoretical Treatment
2013
We compare the plasmonic sensitivity of silver and gold nanorods with similar resonance wavelengths by monitoring the plasmon resonance shift of single noble metal nanorods upon changing the environment from water to sucrose solution. We find that silver nanorods have 1.2 to 2 times higher sensitivity than gold in good agreement with simulations based on the boundary-elements-method (BEM). To exclude the effect of particle volume on sensitivity, we test gold rods with increasing particle width at a given resonance wavelength. Using the Drude-model of optical properties of metal together with the quasi-static approximation (QSA) for localized surface plas-mons, we show that the dominant cont…
Whispering gallery mode resonators coated with Au nanoparticles
2019
Whispering gallery mode resonators (WGMRs) are very interesting for sensing because a resonance shift could be caused by any perturbation of the surrounding environment. Additionally such a resonator is coated with nanomaterials to tailor and enhance the sensitivity for a specific purpose. WGMR were fabricated using standard telecommunication fiber and a hydrogen flame, characterized using the scan method to obtain the quality factors and then coated with gold nanoparticles (Au NPs) using dip coating method and characterized again for comparison. Au NPs were chosen because their positive impact on microresonator sensitivity has been mentioned before and the surface can later be functionaliz…
Quantitative Optical Trapping of Single Gold Nanorods
2008
We report a quantitative analysis of the forces acting on optically trapped single gold nanorods. Individual nanorods with diameters between 8 and 44 nm and aspect ratios between 1.7 and 5.6 were stably trapped in three dimensions using a laser wavelength exceeding their plasmon resonance wavelengths. The interaction between the electromagnetic field of an optical trap and a single gold nanorod correlated with particle polarizability, which is a function of both particle volume and aspect ratio.
Plasmonic Biosensors for the Detection of Lung Cancer Biomarkers: A Review
2021
Lung cancer is the most common and deadliest cancer type globally. Its early diagnosis can guarantee a five-year survival rate. Unfortunately, application of the available diagnosis methods such as computed tomography, chest radiograph, magnetic resonance imaging (MRI), ultrasound, low-dose CT scan, bone scans, positron emission tomography (PET), and biopsy is hindered due to one or more problems, such as phenotypic properties of tumours that prevent early detection, invasiveness, expensiveness, and time consumption. Detection of lung cancer biomarkers using a biosensor is reported to solve the problems. Among biosensors, optical biosensors attract greater attention due to being ultra-sensi…
Dependence of the Optical Constant Parameters of p-Toluene Sulfonic Acid-Doped Polyaniline and Its Composites on Dispersion Solvents
2020
The optical constants of Para-Toluene sulfonic acid-doped polyaniline (PANI), PANIchitosan composites, PANI-reduced graphene-oxide composites and a ternary composite comprising of PANI, chitosan and reduced graphene-oxide dispersed in diluted p-toluene sulfonic acid (PTSA) solution and N-Methyl-2-Pyrrolidone (NMP) solvent have been evaluated and compared. The optical constant values were extracted from the absorbance spectra of thin layers of the respective samples. The potential utilization of the materials as the active sensing materials of surface plasmon resonance biosensors has also been assessed in terms of the estimated value of the penetration depth through a dielectric medium. The …
Covalently linked multimers of gold nanoclusters Au102(p-MBA)44and Au∼250(p-MBA)n
2016
We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au102(p-MBA)44 nanocluster with biphenyl-4,4′-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands. The bands were analyzed by transmission electron microscopy (TEM) revealing monomer, dimer, and trimer fractions of the nanocluster. TEM analysis of dimers in combination with molecular dynamics simulations suggest that the nanoclusters are covalently bound via a disulfide bridge between BP…
Strong coupling between surface plasmon polaritons and β-carotene in nanolayered system.
2013
In this article we experimentally demonstrate the strong coupling between surface plasmon polaritons (SPP) and the S(2) state of β-carotene. The SPPs are excited by prism coupling technique on a thin silver film with β-carotene embedded in a polymer layer on top of that. Rabi splittings with energies 80 and 130 meV are observed in the recorded dispersion relations. Both coupled oscillator model and transfer matrix method are used to fit the experimental results. The scattered radiation of the propagating strongly coupled SPP-S(2) hybrids is collected and an increase of the low energy splitting to 120 meV is observed compared to the reflectivity data. In addition, we performed molecule excit…
Direct optical measurement of light coupling into planar waveguide by plasmonic nanoparticles
2012
Coupling of light into a thin layer of high refractive index material by plasmonic nanoparticles has been widely studied for application in photovoltaic devices, such as thin-film solar cells. In numerous studies this coupling has been investigated through measurement of e.g. quantum efficiency or photocurrent enhancement. Here we present a direct optical measurement of light coupling into a waveguide by plasmonic nanoparticles. We investigate the coupling efficiency into the guided modes within the waveguide by illuminating the surface of a sample, consisting of a glass slide coated with a high refractive index planar waveguide and plasmonic nanoparticles, while directly measuring the inte…
A DNA-nanoparticle actuator enabling optical monitoring of nanoscale movements induced by an electric field.
2018
Merging biological and non-biological matter to fabricate nanoscale assemblies with controllable motion and function is of great interest due to its potential application, for example, in diagnostics and biosensing. Here, we have constructed a DNA-based bionanoactuator that interfaces with biological and non-biological matter via an electric field in a reversibly controllable fashion. The read-out of the actuator is based on motion-induced changes in the plasmon resonance of a gold nanoparticle immobilized to a gold surface by single stranded DNA. The motion of the gold nanoparticle and thus the conformational changes of the DNA under varying electric field were analyzed by dark field spect…
Template-Assembled Synthetic G-Quadruplex (TASQ): A Useful System for Investigating the Interactions of Ligands with Constrained Quadruplex Topologies
2010
A new biomolecular device for investigating the interactions of ligands with constrained DNA quadruplex topologies, using surface plasmon resonance (SPR), is reported. Biomolecular systems containing an intermolecular-like G-quadruplex motif 1 (parallel G-quadruplex conformation), an intramolecular G-quadruplex 2, and a duplex DNA 3 have been designed and developed. The method is based on the concept of template-assembled synthetic G-quadruplex (TASQ), whereby quadruplex DNA structures are assembled on a template that allows precise control of the parallel G-quadruplex conformation. Various known G-quadruplex ligands have been used to investigate the affinities of ligands for intermolecular…