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.

Layer‐by‐layer photocatalyst films made of TiO2 nanoparticles (TiO2NP) assembled with both poly(sodium 4‐styrenesulfonate) (PSS) and graphene oxide (GO) are used for the photodeposition of plasmonic Ag nanoparticles (AgNPs) and subsequently used in surface‐enhanced Raman scattering (SERS). Both photocatalyst films, TiO2NP/PSS and TiO2NP/GO, are capable of driving the formation of AgNP when they are wetted with a drop of AgNO3 diluted solution and submitted to UV irradiation (254 nm). The photodeposition of AgNP, as monitored by UV–vis spectroscopy, follows a first‐order kinetics process in both films and is slightly faster in the TiO2NP/PSS. In addition, scanning electron microscopy reveals that in the TiO2NP/PSS film, the photodeposited AgNPs are larger and isolated, whereas in the TiO2NP/GO film, they are smaller and highly interconnected. The SERS activity of the substrates is evaluated with rhodamine B. When samples are excited in resonance with rhodamine B absorption (514 nm), GO‐based substrates provide the largest enhancement because GO is able to quench the rhodamine B fluorescence, something that PSS is unable to do. Out of this condition (633 nm), the plasmonic effect of AgNP alone prevails regardless of the presence of GO.

Nanotechnologies based on magnetic materials have been successfully used as efficient and reusable strategies to remove pharmaceutical residuals from water. This paper focuses on the fabrication, characterization, and application of ferrite-based magnetic nanoparticles functionalized with L-lysine as potential nanoadsorbents to remove acetylsalicylic acid (ASA) from water. The proposed nanomaterials are composed of highly magnetic and chemically stable core–shell nanoparticles covered with an adsorptive layer of L-lysine (CoFe2O4–g-Fe2O3–Lys). The nanoadsorbents were elaborated using the coprecipitation method in an alkaline medium, leading to nanoparticles with two different mean sizes (13.5 nm and 8.5 nm). The samples were characterized by XRD, TEM, FTIR, XPS, Zetametry, BET, and SQUID magnetometry. The influence of time, pH, and pollutant concentration was evaluated from batch studies using 1.33 g/L of the nanoadsorbents. The Freundlich isotherm best adjusted the adsorption data. The adsorption process exhibited a pseudo-second-order kinetic behavior. The optimal pH for adsorption was around 4-6, with a maximum adsorption capacity of 16.4 mg/g after 150 min of contact time. Regeneration tests also showed that the proposed nanomaterials are reusable. The set of results proved that the nanoadsorbents can be potentially used to remove ASA from water and provide relevant information for their application in large-scale designs.