Dan Wu,Mengnan Hu,Yongyi Zhang,Jing Zhou,Zhaona Wang
Surface enhanced Raman spectroscopy (SERS) is a key nondestructive detecting technology with a broad application demands. However, relative low stability and homogeneity of the SERS substrate hinder its practical applications. Here, a simple and flexible approach is proposed to achieve the arrayed SERS substrates with the periodicity and local randomness by directly growing silver nanoflowers on the patterned wafer fabricated by the optical interference method. By utilizing the hotspot effect of nanogaps within/between the Ag nanoflowers, the SERS substrates demonstrate the low detecting limit of 5 × 10 −10 M and 5 × 10 −9 M in one-dimensional (1D) and two-dimensional (2D) pattern structures for Rhodamine 6G (R6G) probe molecule, respectively. The periodicity assures the fabricated substrate a promising reproducibility and stability. After the 1D array structure is left for 21 days, the intensity of Raman signal of R6G maintains at 80%. Moreover, the proposed method has the advantages of simple preparation, low cost, flexible tunability, and easy-fabrication large scale substrate. The results indicate that the long-range ordered silver nanoflower array structures are promising candidates for the high performance SERS substrate in chemical analysis, medicine and environment monitoring.
Novel three-dimensional Ag nanoflowers (3DAN) were successfully synthesized through a facile Cu2+ mediated solution method using N,N-dimethylformamide (DMF), which serves as both a reducing agent and a solvent at room temperature. It was found that the introduction of a trace amount of Cu2+ could greatly slow the rate of the Ag+ reaction and thus this process effectively reduced the growth speed of Ag nanoparticles allowing 3DAN to be formed. The mechanism underlying the self-assembly process and shape evolution of 3DAN were systematically investigated by varying reaction time. X-Ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the obtained products. X-Ray photoelectron spectroscopy (XPS) was used to assess the chemical state and surface composition of the 3DAN. UV-vis absorption spectra of the products collected from the reaction solution at various stages were taken to study their optical properties. In the measurement of surface-enhanced Raman scattering using rhodamine 6G (R6G) as the probe, the 3DAN exhibited a significant enhancement factor, indicating their potential applications in biosensing and nanodevices.
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