Plasmon-enhanced Stimulated Raman Scattering Microscopy with Single-molecule Detection Sensitivity

Stimulated Raman scattering (SRS) microscopy allows for high-speed label-free chemical imaging of biomedical systems. The imaging sensitivity of SRS microscopy is limited to ~10 mM for endogenous biomolecules. Electronic pre-resonant SRS allows detection of sub-micromolar chromophores. However, label-free SRS detection of single biomolecules having extremely small Raman cross-sections (~10-30 cm2 sr-1) remains unreachable. Here, we demonstrate plasmon-enhanced stimulated Raman scattering (PESRS) microscopy with single-molecule detection sensitivity. Incorporating pico-Joule laser excitation, background subtraction, and a denoising algorithm, we obtained robust single-pixel SRS spectra exhibiting the statistics of single-molecule events. Single-molecule detection was verified by using two isotopologues of adenine. We further demonstrated the capability of applying PESRS for biological applications and utilized PESRS to map adenine released from bacteria due to starvation stress. PESRS microscopy holds the promise for ultrasensitive detection of molecular events in chemical and biomedical systems

OPTIMIZATION OF DRAINAGE NETWORK TO MINIMIZE URBAN FLOODS USING REMOTE SENSING AND GIS TECHNIQUES

The frequency of the occurrence of disasters is increasing day by day. Urban flooding has become one of severe problems faced by Sri Lanka seasonally leading to various social and environmental interruptions. With the increasing of the occurrence it has become a necessity to find a proper solution to overcome the problem. This study was mainly focused to optimize the drainage network in Panadura urban council area, Sri Lanka to minimize the urban flood hazard susceptibility.using Remote Sensing (RS) and Geographical Information System (GIS) techniques. Light Detection AndRanging (LiDAR) Digital Elevation Model (DEM) was utilized to delineate requisite drainage and mini water catchments using Environmental Systems Research Institute (ESRI) Arc Hydro Model. Prior to LiDAR DEM processing an accuracy assessment was performed with respect to the ground truth elevation measured by Total Station and GPS surveys. Current available drainage system in the area was assessed in two ways as alignment and capacity for large water volumes in heavy rainfalls with respect to the delineated natural drainage system. Highly flood vulnerable locations in the current drainage system were identified by performing the comparison of natural drainage network and existing drainage paths. Finally adjustments to the current drainage network and new drainage paths were proposed

Use of Nanoparticle Decorated Surface-Enhanced Raman Scattering Active Sol–Gel Substrates for SALDI-MS Analysis

Spectroscopy and mass spectrometry techniques are sometimes combined into the same analytical workflow to leverage each technique’s analytical benefits. This combined workflow is especially useful in forensic and medical contexts where samples are often precious in nature. Here, we adopt metal nanoparticle (NP) doped sol–gel substrates, initially developed for surface-enhanced Raman scattering (SERS) analysis, as surface-assisted laser desorption/ionization–mass spectrometry (SALDI-MS) substrates. Using dried blood and sample protocols previously developed for SERS analysis, we observe heme-related spectral features on both silver and gold NP substrates by SALDI-MS, demonstrating dual functionality for these orthogonal techniques. Modifying the dried blood extraction procedures also allows for the observation of blood triacylglycerols by SALDI-MS. This is the first demonstration of a SERS/SALDI-MS substrate based on a sol–gel scaffold and the first demonstration of a gold NP sol–gel substrate for SALDI-MS which features lower substrate-related SALDI-MS background compared to the silver substrate.This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Society for Mass Spectrometry, copyright © 2023 American Society for Mass Spectrometry. To access the final edited and published work see DOI: 10.1021/jasms.2c00285. Posted with permission