Fresh Hierarchical Periodic Silver SERS-active Substrate with the Band-aid Protecting Layer†

doi:10.7503/cjcu20180366

Abstract

Abstract:

A novel band-aid like, hierarchical periodic structured, multilayered surface-enhanced Raman scattering(SERS) substrate was developed, which allows a fresh silver surface when peeling off the protector. It was prepared by the vacuum deposition of a thick Ag layer(600 nm) on a hierarchical periodic structured anodic alumina(AAO) that was achieved by anodizing a pre-patterned Al base by means of the nanoimprint lithography with a hard Ni mask, while the AAO layer plays a role of surface protector. Then, the Ag side was glued to a glass slide. When it is used for SERS, the AAO layer can be peeled off to allow for a naked, fresh Ag surface for SERS measurements. This method solves the problem of oxidation and pollution of traditional Ag SERS substrates, ensuring the freshness of the SERS substrate. The AAO preparation steps are largely simplified compared with other AAO preparation procedures. Owing to the use of the nanoimprint lithography, the periodic structure of the Ni stamp can be well copied, which insures the reducibility of the final SERS substrate in SERS measurements. Apparently, the substrate preparation is time-saving and easier, which makes this band-aid like SERS substrate promising for being a commercial SERS substrate.

Key words: Surface-enhanced Raman scattering(SERS) substrate, Anodic alumina(AAO) template, Protective layer

CLC Number:

O647
O657

TrendMD:

XU Weiqing,GUAN Shulin,WANG Yi,WANG Xinnan,TAO Yanchun,XU Shuping. Fresh Hierarchical Periodic Silver SERS-active Substrate with the Band-aid Protecting Layer^†[J]. Chem. J. Chinese Universities, 2018, 39(12): 2752.

Figures/Tables 8

Fig.1 SEM images of patterns on Al and Ag surfaces during the substrate preparation(A) Patterned Al foil after Ni nano-stamping; (B) the achieved AAO after 15 min anodization; (C) AAO after pore size widening; (D) Ag surface copied from the patterned AAO.

Fig.2 SEM images of the AAO templates(A1—D1) and their resulted Ag substrates(A2—D2)with different pore-widen time(A1—D1) AAO templates achieved with the pore-widen time of 40, 70, 100 and 130 min, respectively;(A2—D2) the achieved Ag substrates with the gaps between rods of 69, 29, 19 and 9 nm, respectively.

Fig.3 SERS intensities of 4-Mpy on different SERS substrates with different gap distances between rods5.0 μL of 4-Mpy solution(1.0×10-4 mol/L) was dripped on the substrates and SERS measurement was carried out from five spots on each substrate. Laser power was set as 1.0 μW/cm2 with the accumulation time of 10 s.

Fig.4 SERS spectra from randomly selected 10 points on the same substrate(A) and the intensities of two different peaks at 10 points on one substrate(B)

Fig.5 Comparison of SERS and normal Raman spectra of 4-Mpy5.0 μL of 4-Mpy solution(1.0×10-4 mol/L) was dripped on the substrate to form a 2.40 mm-diameter casting film for recording SERS. 5.0 μL of 4-Mpy solution(0.5 mol/L) was dripped on a silica slide to form a 2.90 mm-diameter casting film for Raman spectrum.

Fig.6 SERS spectra of 4-Mpy(1.0×10-4 mol/L) with the enhancement of fresh Ag nanorod substrate(a) and the air condition exposed(8 month) Ag nanorod substrate(b)

Fig.7 SERS detection of thiramInset: structure of thiram. 5.0 μL of thiram solutions of 6.11×10-4(a), 6.11×10-5(b) and 6.11×10-6 mol/L(c) were dripped on the substrate and dried for SERS measurements.

Fig.8 Scheme 1 Preparation of the hierarchical AAO-based Ag SERS substrate(Ⅰ) and the utilization of this band-aid SERS substrate for measurements(Ⅱ)

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