Una superficie basada en el filtro mejorado de Raman espectroscópico Ensayo para la detección rápida de contaminantes químicos
Summary
Se presenta un procedimiento para la fabricación y la realización de la superficie a base de filtro de Raman espectroscópico (SERS) de ensayo mejorado para la detección de contaminantes químicos (es decir, ferbam pesticidas y antibiótico ampicilina).
Abstract
We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be applied to the detection of various chemical contaminants. Silver nanoparticles (Ag NPs) are synthesized via reduction of silver nitrate by sodium citrate. Then the NPs are aggregated by sodium chloride to form nanoclusters that could be trapped in the pores of the filter membrane. A syringe is connected to the filter holder, with a filter membrane inside. By loading the nanoclusters into the syringe and passing through the membrane, the liquid goes through the membrane but not the nanoclusters, forming a SERS-active membrane. When testing the analyte, the liquid sample is loaded into the syringe and flowed through the Ag NPs coated membrane. The analyte binds and concentrates on the Ag NPs coated membrane. Then the membrane is detached from the filter holder, air dried and measured by a Raman instrument. Here we present the study of the volume effect of Ag NPs and sample on the detection sensitivity as well as the detection of 10 ppb ferbam and 1 ppm ampicillin using the developed assay.
Introduction
Superficie espectroscopia Raman mejorada (SERS) es una técnica que combina la espectroscopia Raman con la nanotecnología. La intensidad de la dispersión Raman de analitos en Noble nano-superficies metálicas es mucho mayor por la resonancia de plasmón de superficie localizada. 1 nanopartículas de plata (Ag NP) son con mucho los SERS más utilizados sustratos debido a su alta capacidad de mejora. 2 Hasta ahora , se han desarrollado diversos métodos de síntesis de Ag NP. 3-6 Ag NP pueden ser usados solos como sustratos SERS eficaces, o combinado con otros materiales y estructuras para mejorar su sensibilidad y / o funcionalidad. 7-11
Técnicas SERS han demostrado una gran capacidad para la detección de diversos contaminantes cantidad traza en alimentos y muestras medioambientales 12 Tradicionalmente, hay dos formas comunes para la preparación de una muestra SERS:.. Los métodos basados en sustrato y basados en solución 13 El metho basado en solucionesd utiliza coloides NP para mezclar con las muestras. A continuación, el complejo NP-analito se recoge mediante centrifugación, y se deposita sobre un soporte sólido para la medición Raman después del secado. El método basado en el sustrato se aplica generalmente mediante el depósito de varios microlitros de muestra de líquido sobre el sustrato sólido pre-fabricados. 14 Sin embargo, ninguno de estos dos métodos son eficaces y aplicables para una gran cantidad de volumen de muestra. Varias modificaciones de los ensayos de SERS superaron los límites de volumen, tales como la integración de un sistema de filtro de 15 a 21 o la incorporación de un dispositivo de microfluidos. 21-24 Los ensayos SERS modificados han mostrado una gran mejora en la sensibilidad y la viabilidad para el control de los contaminantes químicos en grandes muestras de agua.
Aquí demostramos el protocolo detallado de fabricación y aplicación de un método basado SERS filtro de jeringa para detectar trazas de pesticidas y ferbam antibiótico ampicilina.
Protocol
Representative Results
Discussion
Uno de los pasos críticos de este protocolo es la síntesis de Ag NP, donde uniformes NP Ag son la clave para obtener resultados consistentes. El tiempo de calentamiento y las concentraciones de los precursores deben ser controlados con precisión. El tamaño medio de esta preparación AGNPS es 80 nm, que se midió por el Zetasizer (datos no mostrados). Otro paso crítico es la agregación de sal donde la concentración de sal y el tiempo de agregación deben ser controlados con precisión. Además, la elección de la …
Disclosures
The authors have nothing to disclose.
Acknowledgements
This material is based upon work supported by the U.S. Department of Homeland Security under Grant Award Number 2010-ST-061-FD0001 through a grant awarded by the National Center for Food Protection and Defense at the University of Minnesota. Disclaimer: The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security or the National Center for Food Protection and Defense.
Materials
| Ampicillin | Fisher Scientific | BP1760-5 | N/A |
| Ferbam | Chem Service | N-11970-250MG | 98+% |
| Silver nitrate | Sigma Aldrich | 209139 | 99.0+% |
| Sodium citrate dehydrate | Sigma Aldrich | W302600 | 99+% |
| Sodium chloride | Sigma Aldrich | S7653 | 99.5+% |
| EMD Millipore Durapore PVDF Membrane Filters | Fisher Scientific | VVLP01300 | 0.10 µm Pore Size, hydrophilic |
| Polycarbonate Filter Holders | Cole-Parmer | EW-29550-40 | 13 mm diameter |
| Analog Vortex Mixer | Fisher Scientific | 02-215-365 | N/A |
| Nutating Mixers | Fisher Scientific | 05-450-213 | N/A |
| DXR Raman spectroscope | Thermo Scientific | IQLAADGABFFAHCMAPB | Laser power: 1 mW Exposure time: 5 s |
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