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United States Department of Agriculture

Agricultural Research Service

Research Project: Optical Detection of Food Safety and Food Defense Hazards

Location: Quality and Safety Assessment Research Unit

Title: Preparation and characterization of silver particle encapsulated biopolymer nano-colloid substrate for surface enhanced raman scattering (SERS) for biological applications

Authors
item Sundaram, Jaya
item Park, Bosoon
item Lawrence, Kurt
item Yongkuk, Kwon -

Submitted to: American Chemical Society
Publication Type: Abstract Only
Publication Acceptance Date: December 17, 2011
Publication Date: March 27, 2012
Citation: Sundaram, J., Park, B., Lawrence, K.C., Yongkuk, K. 2012. Preparation and Characterization of silver particle encapsulated biopolymer nano-colloid substrate for surface enhanced raman scattering (SERS) for biological applications [abstract]. American Chemical Society. ACS meeting, March 25-29, Santiago, USA.

Interpretive Summary: Raman spectroscopy gives light scattering to detect and characterize various properties of biological and non-biological materials. In practice Raman scattering is very weak and it needs to be enhanced to detect and characterize biological materials. To get enhanced Raman scattering (SERS) creation of patterned roughened surface substrates are needed. Several methods have been developed to make SERS substrates for biological sample detection. Most of the substrate preparation methods however, need extensive procedures and expensive equipments, also the substrate are sometimes unstable. Therefore preparation of more stable substrate using simple procedure for biological sample detection is the current priority in SERS research. To achieve stable SERS substrate for biological sample detection, a silver nano particle encapsulated biopolymer colloid was prepared in this work. Silver colloid encapsulated biopolymer was coated on the food grade stainless steel plates. This was used as biopolymer metal substrate for SERS. Substrate was measured for its optical properties using hyperspectral microscopic imaging system and UV-Visible spectrometer. Also their detection limits were checked using standard chemicals such as BPE and Rhodamine G.

Technical Abstract: To detect biological samples such as foodborne pathogens, Surface Enhanced Raman Scattering (SERS) substrate was prepared and its characteristics were analyzed in this work. Silver biopolymer nano colloidal substrate was prepared by adding silver nitrate to 2% polyvinyl alcohol (PVA) solution and reduced the silver nitrate into silver ion using 1 % trisodium citrate by following the Lee-Meisel method. Optical properties of substrate Plasmon were measured using UV-VIS spectroscopy and hyperspectral microscopy. Surface morphology was analyzed using transmission electron microscopy. Detection limit was found by measuring the signals of BPE and Rhodamine G at various concentrations (from 10-4 up to 10-8 M) and found that it can detect BPE as low as 10-6 M concentration and Rhodamine G as low as 10-8 M concentration. Substrates reproducibility was checked by comparing the mean and standard deviation of SERS signals of BPE and Rhodamine G measured at 20 different spots on the substrate that were prepared and scanned at different times. Shelf life in terms of substrate stability was checked by keeping the substrate for 10 months and they were used to measure the SERS signals of BPE and Rhodamine G at 10-5 and 10-6 concentration respectively. SERS signals obtained using freshly made substrate and stored substrate were compared and found that both the signals were similar with respect to SERS intensity. SERS mapping was conducted to validate active surface uniformity of the substrate.

Last Modified: 8/29/2014
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