Three‐Dimensional TiO₂−Ag Nanopore Arrays for Powerful Photoinduced Enhanced Raman Spectroscopy (PIERS) and Versatile Detection of Toxic Organics

Abstract

It is highly desirable to readily detect the residues of toxic organics in the field with a portable device. Herein, we report a photo-induced enhanced Raman spectroscopy (PIERS) technique combined with a portable Raman approach to detect toxic analytes at trace levels. A new type of TiO 2 ÀAg nanopore array as a powerful PIERS substrate was fabricated by depositing Ag nanoparticles on TiO 2 nanopores. This semiconductor-metal three-dimensional hybrid nanostructure achieved an 8-fold PIERS enhancement over normal SERS due to the light-induced charge transfer from TiO 2 to the Ag nanoparticles upon UV irradiation. In particular, this PIERS substrate exhibited excellent detection of a variety of toxic substances. A low concentration of 10 À9 M for antiseptics (Crystal violet) and 10 À5 M for pesticides (carbaryl, phoxim and thiram) could be readily detected by a portable Raman device. Meanwhile, the successful incorporation of plasmonic Ag nanoparticles in TiO 2 nanopores further enhanced the photocatalytic ability and the structure is robust enough for multiple reuse cycles. The demonstrated PIERS technique may become an effective way for enhancing Raman scattering, which has great potential for portable Raman detections.[a] Prof.

Highly Efficient Photoinduced Enhanced Raman Spectroscopy (PIERS) from Plasmonic Nanoparticles Decorated 3D Semiconductor Arrays for Ultrasensitive, Portable, and Recyclable Detection of Organic Pollutants

“…The detailed reference values for enhancement calculation are displayed in Table S1. It is worth noting that these significant enhancement magnitudes from mixed-phase TiO 2 −Ag substrates are much larger than that from single-phase TiO 2 (A)/ AgNPs nanopore array with an 8-fold PIERS enhancement 46 and TiO 2 (R)/Au film which has with a 10-fold PIERS enhancement. 22 Improved Detection Sensitivity Based on PIERS Technique.…”

New Mechanism for Long Photo‐Induced Enhanced Raman Spectroscopy in Au Nanoparticles Embedded in TiO2

“…PIERS has already been demonstrated successful on a diversity of molecules: Raman probes, [27][28][29]31] biomolecules (DNA, [32] tyrosine, [33] and glucose [27] ), explosives, [27,34] and organic pollutants. [35,36] It has also been used for the study of V O dynamics in semiconductors. [37,38] Nevertheless, this technique is still young and, as Zhao et al are pointing out in their 2021 review, [39] several issues must still be addressed.…”

Highly crystalline ZnO film decorated with gold nanospheres for PIERS chemical sensing

“…The only demonstration of this PIERS effect from a ZnO film with Au nanoparticles was facing significant fluctuations of the signal due to a weak crystallinity 14 . Besides, a small number of research groups demonstrated this PIERS effect but based on a film or nanopore array of titanium dioxide covered by Au or Ag nanoparticles 15,16 , or else based on aligned diphenylalanine peptide nanotubes covered with silver nanoparticles 17 . With our novel substrates, the chemical molecules will be adsorbed on plasmonic nanoparticles enabling a SERS enhancement by two potential contributions: electromagnetic and/or chemical 18-20 . In our paper, only the chemical contribution is investigated because the plasmon resonance of gold nanoparticles on the highly crystalline ZnO film (λ plasmon = 555 nm) is far from the excitation wavelength for PIERS/SERS measurements (λ exc = 633 nm, see figure 1) inducing a very weak SERS signal.…”