Dataset for SERS plasmonic array: Width, spacing, and thin film oxide thickness optimization

Surface-enhanced Raman spectroscopy (SERS) improves the scope and power of Raman spectroscopy by taking advantage of plasmonic nanostructures, which have the potential to enhance Raman signal strength by several orders of magnitude, which can allow for the detection of analyte molecules. The dataset presented provides results of a computational study that used a finite element method (FEM) to model gold nanowires on a silicon dioxide substrate. The survey calculated the surface average of optical surface enhancement due to plasmonic effects across the entire model and studied various geometric parameters regarding the width of the nanowires, spacing between the nanowires, and thickness of the silicon dioxide substrate. From this data, enhancement values were found to have a periodicity due to the thickness of the silicon dioxide. Additionally, strong plasmonic enhancement for smaller distances between nanowires were found, as expected; however, additional surface enhancement at greater gap distances were observed, which were not anticipated, possibly due to resonance with periodic dimensions and the frequency of the light. This data presentation will benefit future SERS studies by probing further into the computational and mathematical material presented previously

The Role of Rayleigh-Wood Anomalies and Surface Plasmons in Optical Enhancement for Nano-Gratings

We propose and report on the design of a 1-D metallo-dielectric nano-grating on a GaAs substrate. We numerically study the impact of grating period, slit and wire widths, and irradiating angle of incidence on the optical response. The optimal wire width, w = 160 nm, was chosen based on previous results from investigations into the influence of wire width and nano-slit dimensions on optical and electrical enhancements in metal-semiconductor-metal photodetectors. In this present project, resonant absorption and reflection modes were observed while varying the wire and nano-slit widths to study the unique optical modes generated by Rayleigh-Wood anomalies and surface plasmon polaritons. We observed sharp and diffuse changes in optical response to these anomalies, which may potentially be useful in applications such as photo-sensing and photodetectors. Additionally, we found that varying the slit width produced sharper, more intense anomalies in the optical spectrum than varying the wire width

Colonic mucosal changes in Egyptian patients with liver cirrhosis and portal hypertension

Background and aims In patients with liver cirrhosis and portal hypertension (PHT), portal hypertensive colopathy (PHC) is thought to be an important cause of lower gastrointestinal bleeding. This study aimed at evaluating the prevalence and clinical significance of colonic mucosal changes in Egyptian patients with liver cirrhosis and PHT. Patients and methods A prospective study was conducted on 35 patients with liver cirrhosis and PHT (proved by upper endoscopy and/or abdominal ultrasonography). They were evaluated using full colonoscopy to detect changes in colonic mucosa and using gastroscopy to detect the presence of both gastroesophageal varices and portal hypertensive gastropathy. Results Colonic lesions were found in 27 patients (77.1%), including haemorrhoids in 20 patients (57.1%), diffuse hyperaemic mucosa in 16 patients (45.7%), angiodysplastic lesions in 12 patients (34.3%) and rectal varices in five patients (14.3%). Bleeding per rectum was detected in seven patients (20%), and it significantly correlated with the presence of haemorrhoids (P = 0.02). The prevalence of PHC and the presence of haemorrhoids increased with the worsening Child-Pugh class (P = 0.01 and 0.02, respectively). Conclusion The prevalence of PHC and haemorrhoids increases with the progression of liver disease and worsening of the Child-Pugh grading in cirrhotic patients. However, haemorrhoids, rectal varices, hyperaemia and colonic angiodysplasia are not affected by the presence of portal hypertensive gastropathy

Study IR- Raman Spectra properties of Aluminium Phosphide Diamondoids Nanostructures via DFT

Density Functional Theory has been utilized to investigate the electronic and structural characteristics of Aluminium phosphide (AlP). The exchange-correlation potential was calculated using the Generalized Gradient Approximation. The structural, electronic and vibrational features of AlP diamondoids and nanocrystals were investigated using Density Functional Theory at the PBE/6-31(d) level, which included polarization functions. Vibrational modes have been optimized concerning IR intensity, force constants, and lowered masses. In this study there are two components to the vibrational force constant for AlP diamondoids. The first one is distinguished by a reduced mass that is greater than 1 amu and consists primarily of Al-P vibrations that are positioned roughly between 0 and 231 cm-1. The second component has a decreased mass very near to 1 amu and is in the 1228–2400 cm–1 range. It is entirely made up of hydrogen vibrational modes. AlP diamondoids were evaluated with the results of experimental bulk in terms of molecular size-related changes in allocated vibrational frequencies

The Role of Rayleigh-Wood Anomalies and Surface Plasmons in Optical Enhancement for Nano-Gratings

We propose and report on the design of a 1-D metallo-dielectric nano-grating on a GaAs substrate. We numerically study the impact of grating period, slit and wire widths, and irradiating angle of incidence on the optical response. The optimal wire width, w = 160 nm, was chosen based on previous results from investigations into the influence of wire width and nano-slit dimensions on optical and electrical enhancements in metal-semiconductor-metal photodetectors. In this present project, resonant absorption and reflection modes were observed while varying the wire and nano-slit widths to study the unique optical modes generated by Rayleigh-Wood anomalies and surface plasmon polaritons. We observed sharp and diffuse changes in optical response to these anomalies, which may potentially be useful in applications such as photo-sensing and photodetectors. Additionally, we found that varying the slit width produced sharper, more intense anomalies in the optical spectrum than varying the wire width

Visualization 1: Improved optical enhancement using double-width plasmonic gratings with nanogaps

Visualization 1 Originally published in Photonics Research on 01 October 2016 (prj-4-5-173

Plasmonic Au Array SERS Substrate with Optimized Thin Film Oxide Substrate Layer

This work studies the effect of a plasmonic array structure coupled with thin film oxide substrate layers on optical surface enhancement using a finite element method. Previous results have shown that as the nanowire spacing increases in the sub-100 nm range, enhancement decreases; however, this work improves upon previous results by extending the range above 100 nm. It also averages optical enhancement across the entire device surface rather than localized regions, which gives a more practical estimate of the sensor response. A significant finding is that in higher ranges, optical enhancement does not always decrease but instead has additional plasmonic modes at greater nanowire and spacing dimensions resonant with the period of the structure and the incident light wavelength, making it possible to optimize enhancement in more accessibly fabricated nanowire array structures. This work also studies surface enhancement to optimize the geometries of plasmonic wires and oxide substrate thickness. Periodic oscillations of surface enhancement are observed at specific oxide thicknesses. These results will help improve future research by providing optimized geometries for SERS molecular sensors

Dataset for SERS Plasmonic Array: Width, Spacing, and Thin Film Oxide Thickness Optimization

Surface-enhanced Raman spectroscopy (SERS) improves the scope and power of Raman spectroscopy by taking advantage of plasmonic nanostructures, which have the potential to enhance Raman signal strength by several orders of magnitude, which can allow for the detection of analyte molecules. The dataset presented provides results of a computational study that used a finite element method (FEM) to model gold nanowires on a silicon dioxide substrate. The survey calculated the surface average of optical surface enhancement due to plasmonic effects across the entire model and studied various geometric parameters regarding the width of the nanowires, spacing between the nanowires, and thickness of the silicon dioxide substrate. From this data, enhancement values were found to have a periodicity due to the thickness of the silicon dioxide. Additionally, strong plasmonic enhancement for smaller distances between nanowires were found, as expected; however, additional surface enhancement at greater gap distances were observed, which were not anticipated, possibly due to resonance with periodic dimensions and the frequency of the light. This data presentation will benefit future SERS studies by probing further into the computational and mathematical material presented previously