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Félix Massa, Tamara Y.

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    Vibrational spectrocopy for detection of chemical and biological threats and other important targets adsorbed on Au and Ag nanoparticles
    (2026-05-16) Félix Massa, Tamara Y.; Félix Massa, Tamara Y.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Mina Camilde, Nairmen; Torres Candelaria, Jessica; Bezares Salinas, Francisco J.; Estremera Andújar, Rafael A.; Department of Chemistry; Pérez Muñoz, Fernando
    Detection of Chemical and Biological Threats (CBT), particularly in defense and security applications, plays a crucial role when the safety and security of first responders, government personnel, and civilians are at risk. Spectroscopy provides a powerful tool for rapidly and accurately identifying, detecting, and quantifying techniques of CBTs. Raman Scattering (RS) and Mid-Infrared (MIR) spectroscopies have received special attention as powerful vibrational spectroscopy techniques. For RS, one of its applications that has experienced a significant upturn in recent decades is SERS, which has the added advantage of detecting carbon-based trace compounds (including CBTs) at trace levels. On the other hand, SEIRA is an MIR application that enhances the detection of CBTs at the trace level. Gold or silver nanomaterials are excellent sources for SERS and SEIRA materials due to their ease of preparation and high sensitivity. In this research, we report a simple, fast, and reproducible method for preparing SERS and SEIRA active substrates for detecting and quantifications CBTs at the trace level. For detection and quantification, Raman and Mid-Infrared Laser Spectroscopy (MIRLS) using a Quantum Cascade Laser (QCL) operating at a grazing angle of incidence were employed. For CBTs, sensor preparation, synthesis, and characterization of gold nanorods were achieved. We used stainless-steel substrates coated with gold nanorods (AuNRs) as a deposition method using a chemical printer. The sensor can detect TATP, HMX, PETN, L-Tryp, L-His, Staphylococcus aureus (Sa), Staphylococcus epidermis (Se), Micrococcus luteus (Ml), and Escherichia coli (Ec) at trace level (~ 10 ppb).
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    Consecutive solvent – C60 exchange on (η2– C60) Ir(CO)Cl(PPh3)2 and catalytically significant organometallic reactions on Ir(CO)(PPh3)2Cl(Solvent)
    (2010) Félix Massa, Tamara Y.; Cortés Figueroa, José E.; College of Arts and Sciences - Sciences; Cádiz García, Mayra E.; Meléndez Martínez, Enrique; Department of Chemistry; Acevedo Rullán, Aldo
    The solvent/C60 exchange reactions on (η2 – C60)Ir(CO)(PPh3)2Cl (solvent = benzene and cyclohexane) are biphasic. Plots of absorbance values at 550 nm vs. time are biexponential. Experiments where the reactions were monitored by infrared spectroscopy and 1HNMR spectrometry permitted identification of the consecutive processes suggested by absorbance (550 nm) vs. time plots. The first segment of absorbance vs. time plots was assigned to C60/benzene exchange producing (benzene)Ir(CO)(PPh3)2Cl, whereas the corresponding second segment was attributed to a series of reactions involving C-H bond oxidative cleavage of η 2 -coordinated benzene followed by a series of catalytically-relevant reactions. Activation parameters for benzene/C60 exchange reactions on (η2 – C60)Ir(CO)(PPh3)2Cl suggested an interchange associative mechanism. This interpretation prompted kinetics studies of the reactions in benzene/cyclohexane mixtures to determine rate constant values without unresolved solvent concentration dependences. Interestingly, rate constant values obtained from the second segment of the plot were [solvent]-dependent, suggesting the existence of benzene-cyclohexane exchange on the solvated (benzene)Ir(CO)(PPh3)2Cl and (cyclohexane)Ir(CO)(PPh3)2Cl intermediates. The proposed mechanism was tested by monitoring the reactions by infrared spectroscopy and 1HNMR spectrometry of actual samples of commercially available Vaska’s compound. These experiments confirmed that once the solvated intermediates are produce they undergo C-H bond oxidative cleavage followed by a series of parallel PPh3 dissociation and σ-complexes formation.