Self-Assembled Ag-Cu₂O Nanocomposite Films at Air-Liquid Interfaces for Surface-Enhanced Raman Scattering and Electrochemical Detection of H₂O₂

Abstract

We employ a facile and novel route to synthesize multifunctional Ag-Cu₂O nanocomposite films through the self-assembly of nanoparticles at an air-liquid interface. In the ethanol-water phase, AgNO₃ and Cu(NO₃)₂ were reduced to Ag-Cu₂O nanoparticles by NaBH₄ in the presence of cinnamic acid. The Ag-Cu₂O nanoparticles were immediately trapped at the air-liquid interface to form two-dimensional nanocomposite films after the reduction reaction was finished. The morphology of the nanocomposite films could be controlled by the systematic regulation of experimental parameters. It was found that the prepared nanocomposite films serving as the substrates exhibited strong surface-enhanced Raman scattering (SERS) activity. 4-aminothiophenol (4-ATP) molecules were used as the test probes to examine the SERS sensitivity of the nanocomposite films. Moreover, the nanocomposite films synthesized by our method showed enhanced electrocatalytic activity towards hydrogen peroxide (H₂O₂) and therefore could be utilized to fabricate a non-enzymatic electrochemical H₂O₂ sensor.

Keywords: SERS; air–liquid interface; electrochemistry; nanocomposite films; self-assembly; sensor.

Figure 1

Photograph of the 2D Ag-Cu₂O nanocomposite film formed at the air-liquid interface (Marked with white rectangle).

Figure 2

SEM images of the Ag-Cu₂O nanocomposite films prepared by adjusting the concentration of CA as (a) 1 mM; (b) 3 mM; (c) 9.6 mM; (d) EDS analysis of (b).

Figure 3

XPS spectra of (a) Ag 3d and (b) Cu 2p of the as-prepared Ag-Cu₂O nanocomposite film, and (c) Cu 2p of the Cu₂O nanoparticle film.

Figure 4

(A) SERS spectra of 4-ATP on different Ag-Cu₂O nanocomposite films obtained by tuning the concentration of CA as (a) 1 mM, (b) 3 mM, and (c) 9.6 mM; (B) The normal Raman spectra of solid 4-ATP.

Figure 5

SERS spectra of 4-ATP on the Ag-Cu₂O nanocomposite films prepared by adjusting the molar ratio of AgNO₃ to Cu(NO₃)₂; (a) 3:1, (b) 1:1, and (c) 1:3.

Figure 6

SEM images of the Ag-Cu₂O nanocomposite films prepared by tuning the molar ratio of AgNO₃ to Cu(NO₃)₂; (a) 1:1 and (b) 1:3.

Figure 7

(a) Typical i-t response curve of nanocomposite-film/GCE upon successive additions of different amounts of H₂O₂ into 0.1 M PBS at −0.25 V. The inset is the early i-t response from 200 s to 900 s; (b) calibration curve; (c) selectivity of the sensor.