Understanding the effects of synthetic parameters in the catalytic activity of heterogeneous catalysts is of utmost importance when aiming for optimal reaction conditions. Hence, we disclose in this work the synthesis and characterization of cerium-modified MCM-41 materials. In addition, it was observed for the first time, differences in catalytic activity when using different cerium synthetic precursors: CeCl₃·7H₂O and Ce(NO₃)₃·6H₂O (Ce-MCM-Cl and Ce-MCM-NO₃, respectively). A mechanism for cerium incorporation in MCM-41 was proposed, where [Ce(OH)₃] species were hydrogen bonded to silicate anions, forming framework Ce-O-Si bonds during condensation and, consequently, causing distortion of the typical hexagonal mesophase. It was also observed that Ce(OH)₃ formed aggregated layers with template assemblies during synthesis, resulting in non-framework CeO₂ species on the MCM-41 surface after calcination. These CeO₂ species were preferentially formed for Ce-MCM-NO₃ and were attributed to the nitrate ions’ strong binding to template molecules. In the solvent free liquid-phase oxidation of benzyl alcohol (BzOH), Ce-MCM-Cl achieved better BzOH conversions and benzaldehyde (BzD) yields, while Ce-MCM-NO₃ offered increased BzD selectivity. The catalysts’ reusability was also studied over three catalytic runs, where Ce-MCM-NO₃ was more resistant than Ce-MCM-Cl towards deactivation. The observed catalytic behavior shows the importance of metal precursors in the obtainment of materials with desirable final properties.

Detection of illegal drugs in fingermarks is a routine activity of the scientific police and it can be better carried out with the help of more sensitive and faster analytical tools. In this regard, this contribution proposes and tests a SERS-based method for the rapid detection of cocaine hydrochloride (COC) in latent fingerprints (LFP) using photochemically-made CTAB-coated gold nanorods (AuNRs) as SERS-active substrates. As a key point, removal of excessive CTAB from the AuNR colloids is essential to achieve the largest Raman signal enhancement. The method is capable of detecting COC in dried solutions (∼1 nM) and in either male or female COC-doped LFPs (∼60 µM). The latter corresponds to ∼300 ng, which falls within the range reported for COC excreted through sweat. The method was also tested for its predominant metabolite, benzoylecgonine (BENZ), which exhibited a similar performance. Adsorption of analytes on AuNRs was investigated with the aid of different isotherm models. Freundlich and Frumkin models were the best and revealed that COC and BENZ are equally physiosorbed (ΔG⁰ _ads ∼ −30 kJ mol⁻¹) onto a heterogenous surface (AuNRs) with a discrete attractive interaction between adsorbed species. Considering that the photochemical synthesis is completed in about 30 min, and that staining of LFPs is easily done, photochemically-made AuNRs offer a relatively simple yet very sensitive method for assisting in COC detection.