Photocatalytic Method for the Simultaneous Synthesis and Immobilization of Ag Nanoparticles onto Solid Substrates

Abstract

A photocatalytic method based on layer-by-layer photocatalyst films made of titanium dioxide nanoparticles and graphene oxide, TiO 2 NPs/GO, is proposed for performing the synthesis and immobilization of spherical AgNPs simultaneously using diluted AgNO 3 solutions and UV irradiation (254 nm). The novelty provided by this method is that the amount and aggregation extent of AgNPs can be controlled by the number of TiO 2 NP/GO bilayers and the composition of the outermost layer in the photocatalyst film. When the outermost layer is made of GO, more AgNPs are deposited because GO serves as an anchoring harbor for Ag + ions and a venue to the transportation of photoexcited electrons for subsequent photo reduction to Ag 0 . The photodeposition follows a first-order kinetics, whereas in the equilibrium it can be fitted by the Langmuir isotherm model for which surface coverage as high as 60% is attained after 70 min of UV irradiation. The TiO 2 NP/GO/AgNP substrates show surface-enhanced resonant Raman scattering (SERRS) activity for nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium salt (NiTsPc). The SERRS activity is ascribed to a combination of local electromagnetic field enhancement because of the plasmon resonance of AgNPs and proper excitation of samples in resonance with the Q-band of NiTsPc.

A Reciprocal-Amplifiable Fluorescence Sensing Platform via Replicated Hybridization Chain Reaction for Hosting Concatenated Multi-Ag Nanoclusters as Signal Reporter

“…Obviously, the blank was nonabsorptive, while mgAgNCs at λ max = 490 nm was found in the presence of T. This was resulted from the complexation of Ag + with N/O atoms in the template bases, 33−35 and the hosted cluster concatemers with newly overlapped electronic bands were well-known, having UV−vis absorption in this spectral region. 35,36 Fluorescence Response of rHCR-Guided mgAgNCs Concatemers. The 2D and 3D fluorescence contour maps of mgAgNCs without and with T were recorded at λ ex /λ em = 490/ 550 nm.…”

“…Obviously, the blank was nonabsorptive, while mg AgNCs at λ max = 490 nm was found in the presence of T . This was resulted from the complexation of Ag + with N/O atoms in the template bases, − and the hosted cluster concatemers with newly overlapped electronic bands were well-known, having UV–vis absorption in this spectral region. , …”

The Role Played by Graphene Oxide in the Photodeposition and Surface‐Enhanced Raman Scattering Activity of Plasmonic Ag Nanoparticle Substrates

“…The water used in all experimental procedures was of ultrapure type (resistivity: 18 MΩ cm), provided by a Milli‐Q Millipore purification system. Individual aqueous suspensions of cationic TiO 2 NP (43.7 ± 0.9 nm; zeta potential = +38.7 ± 1.7 mV) and anionic GO (280 ± 30 nm; zeta potential = −57.3 ± 0.5 mV) were prepared as described in previous studies . PSS (M w = 70 000 g mol −1 ) was purchased from Sigma‐Aldrich (Brazil).…”