Eco-Friendly Fabrication of Plasmonically Active Substrates Based on End-Grafted Poly(ethylene glycol) Layers

Abstract

We report completely sustainable processes and materials for inexpensive and scalable fabrication of plasmonically active solid substrates, which are critical for emerging applications in sensing, catalysis, and metasurfaces. Our approach involves grafting of poly(ethylene glycol) (PEG) onto silicon oxide terminated solid substrates using all-water based processing leading to an ultrathin (12 nm) and smooth (roughness of ∼1 nm) functional layer. The resulting surfaces facilitate robust and effective immobilization of gold nanoparticles (NPs) with a density that is superior to the organic solvent based processing. This new process achieves size dependent assembly of the citrate-stabilized gold NPs resulting in high plasmonic activity in surface-enhanced Raman scattering (SERS). The use of leaf extracts derived from Quercus pubescens as a reducing and stabilizing agent allowed for green synthesis of gold NPs with an average diameter of 25.6 ± 11.1 nm. The assembly of the green synthesized gold NPs on all-water processed PEG grafted layers enabled a fully sustainable route for fabrication of plasmonically active solid substrates. The resulting substrates exhibited high SERS response over the entire (∼1 cm 2 ) substrate surface with an analytical enhancement factor of 9.48 × 10 4 for the probe molecule rhodamine 6G under 532 nm laser excitation. A microfluidic device was also constructed on the fabricated platform for SERS mediated simultaneous detection of two nonsteroidal anti-inflammatory drugs, dexketoprofen and ibuprofen, which are widely used in human medicine and present as contaminants in wastewater. The biocompatibility of PEG together with all-water based processing overcome the need for waste management and ventilation of the working place enabling cost and energy efficient, environmentally benign fabrication of plasmonic devices.

Chemical Funneling of Colloidal Gold Nanoparticles on Printed Arrays of End-Grafted Polymers for Plasmonic Applications

“…For a grafting density of 0.36 chain/nm 2 , the distance between grafting sites is 1.88 nm, which is smaller than twice the radius of gyration of PEG (R g = 6.9 nm), confirming that end-grafted PEG layers are in the brush regime. 43 Note that the grafting density of ∼0.36 chain/nm 2 and height of 19.3 nm are significantly high when compared with previously reported homogeneous PEG layers 44 prepared by spin-coating of similar materials.…”

Antibacterial, Antiviral, and Self-Cleaning Mats with Sensing Capabilities Based on Electrospun Nanofibers Decorated with ZnO Nanorods and Ag Nanoparticles for Protective Clothing Applications

“…These results suggest that AgNPs facilitate plasmonic hot spots that effectively concentrate electromagnetic fields at/near the metallic surfaces and increase the signal amplitude by several orders of magnitude. 56,57 To understand the effect of Ag NP concentration on the SERS activity, the Raman spectrum was measured after a 1 mM MB analyte molecule was dropped on NF mats prepared using different Ag loadings. As shown in Figure 6b, the highest intensity of the SERS spectrum of MB was obtained after utilizing of a NF with 1 wt %.…”

Machine Learning-Assisted Pesticide Detection on a Flexible Surface-Enhanced Raman Scattering Substrate Prepared by Silver Nanoparticles

“…This situation necessitates the development of SERS substrates with green synthesis methods that include environmentally friendly materials and processes. − Green synthesis, especially the ones based on plant extracts, is the ideal approach due to availability and renewability of a wide range biomass, as well as the environmental friendliness of post-synthesis waste products. Therefore, there is a growing number of studies that report the preparation of various SERS-active substrates using green techniques and materials. − Ankamwar et al reported the green synthesis of Ag nanoparticles (NPs) using the plant extract as reducing and stabilizing agents and employed it as an effective SERS substrate as well as a catalyst. , In another study, Ag NPs are reduced on graphene oxide using the leaf extract of Psidium guajava and used as a SERS platform to detect methylene blue …”