Office paper decorated with silver nanostars - an alternative cost effective platform for trace analyte detection by SERS

Abstract

For analytical applications in portable sensors to be used in the point-of-need, low-cost SERS substrates using paper as a base, are an alternative. In this work, SERS substrates were produced on two different types of paper: a high porosity paper (Whatman no. 1); and a low porosity paper (commercially available office paper, Portucel Soporcel). Solutions containing spherical silver nanoparticles (AgNPs) and silver nanostars (AgNSs) were separately drop-casted on hydrophilic wells patterned on the papers. The porosity of the paper was found to play a determinant role on the AgNP and AgNS distribution along the paper fibres, with most of the nanoparticles being retained at the illuminated surface of the office paper substrate. The highest SERS enhancements were obtained for the office paper substrate, with deposited AgNSs. A limit of detection for rhodamine-6G as low as 11.4 ± 0.2 pg could be achieved, with an analytical enhancement factor of ≈107 for this specific analyte. The well patterning technique allowed good signal uniformity (RSD of 1.7%). Besides, these SERS substrates remained stable after 5 weeks of storage (RSD of 7.3%). Paper-induced aggregation of AgNPs was found to be a viable alternative to the classical salt-induced aggregation, to obtain a highly sensitive SERS substrates.

Surface Plasmon Resonances in Silver Nanostars

“…This dependence has motivated the synthesis of metallic NPs with different morphologies [ 13 , 24 ], especially the highly anisotropic NPs such as nanostars (NSs) and nanoplates (NPLs), where the field enhancement of the tip plasmons may result in more efficient SERS [ 25 ]. In one of the latest advances [ 13 ], silver nanostars (Ag-NSs) have provided high SERS performance [ 26 , 27 , 28 ]. The work in this field has been focused on the control of morphology and empirical mechanisms to further enhance the electromagnetic field, while less attention has been given to a theoretical interpretation of some of the observed phenomena.…”

“…The work in this field has been focused on the control of morphology and empirical mechanisms to further enhance the electromagnetic field, while less attention has been given to a theoretical interpretation of some of the observed phenomena. For example, the extinction spectra of Ag-NSs display a tail at large wavelengths ( nm) which is attributed to nanoparticle aggregation and scattering by different morphologies of Ag-NSs and tip sharpnesses [ 13 , 26 , 27 , 28 ].…”

New trends in plasmonic (bio)sensing

“…By controlling the shape of the nanostructures, one can control the ways in which electrons oscillate, consequently tuning how the nanostructure scatters and/or absorbs light, and enhances local EM fields (Tiwari et al 2007). Nanostructures containing sharp protrusions, such as nanostars (Hao et al 2007, Chatterjee et al 2016, Atta et al 2016, Oliveira et al 2017), nanorices (Wei et al 2010 and bipyramids (Le Ru et al 2011, Niu et al 2017, and also sharp corners, as nanorods (Yang et al 2012, Sivapalan et al 2013, Greeneltch et al 2013, Kumar et al 2014), nanotriangles (Sherry et al 2006, Haes and Van Duyne 2002, Scarabelli et al 2014, nanoprisms (Métraux andMirkin 2005, Ciou et al 2009) and nanocubes (McLellan et al 2007, have been designed to create regions with strongly enhanced EM fields, i. e., the hot spots. Fig.…”

Electrokinetically-Driven Assembly of Gold Colloids into Nanostructures for Surface-Enhanced Raman Scattering

“…Previous groups have investigated the assembly of gold nanoparticles from microscale or nanoscale electrodes, for the purposes of forming nanowires for nanoscale electronic devices [11][12][13][14][15]. Other groups have used gold nanoparticles deposited onto solid substrates [16,17], or in colloidal suspension, directly [18], for SERS detection. However, in these examples, the ionic composition of the fluid matrix is not considered.…”