Fierro Mercado, Pedro M.

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2005 - 200912010 - 20121
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    𝘐𝘯 𝘴𝘪𝘵𝘶 FT-IR fiber optic method for detection of active pharmaceutical ingredients (APIs) and excipients on metallic substrates
    (2005) Fierro Mercado, Pedro M.; Hernandez Rivera, Samuel P.; College of Arts and Sciencies - Sciences; Mina, Nairmen; Scott, Ismael; Department of Chemistry; Mehta, Narinder
    A simple, rapid and low-cost method is presented as a new alternative for the detection of organic compounds on surfaces. This method uses an optical fiber coupled to a Grazing Angle Probe-Fourier Transform Infrared Spectrometer which makes it remote sensed and applicable for direct detection of contaminant left on surfaces of pharmaceutical reactors. Besides, it is solvent free and requires no sample preparation. Smearing deposition was used for transferring the compounds on the substrates to be used as standards. Samples of an active pharmaceutical ingredient (API) from Bristol-Myers Squibb in Humacao, Puerto Rico and magnesium stearate as excipient ranging from 0.07 to 10.0 μg/cm² were deposited on stainless steel metal surfaces. Methanol was used as transfer solvent for smearing. The amount of analyte was related to the intensity of the absorption band due to fundamental vibrations of the analyte in the fingerprint region of the infrared spectra. Multivariate calibration procedure using partial least square (PLS) regression and discriminant analysis by principal component analysis (DA-PCA) to establish the relationship between the deposited amount of analyte and the intensity of the infrared signals were used. The proposed method has a limit of detection 280 ng/cm² with a relative error of 3.57%.
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    Thermal inkjet technology for the deposition of nanoparticles and Metal-organic framework (Mof): Preparation of sers-active substrates and Mof films for In-situ enhanced raman and infrared detection of harmful contaminants
    (2012-12) Fierro Mercado, Pedro M.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Mina, Nairmen; Perales, Oscar; Fernández, Félix; Department of Chemistry; Briano, Julio
    The applications of thermal ink-jet printing technology as deposition technique of functional materials such as metal nanoparticles and microporous nickel-oxalate metal organic framework were studied. Highly sensitive surface-enhanced Raman spectroscopy (SERS) substrates capable of detecting a few hundred of molecules were prepared by depositing silver nanoparticles. The silver films were prepared by printing silver nanoparticles (Ag-NP) suspension over quartz substrates. Substrates were characterized by UV-Vis spectroscopy and the morphological evolution of the films was monitored by atomic force microscopy. Inhomogeneous coverage of Ag nanoparticles were obtained at only one deposition while a more uniform distribution of Ag NP were shown when number of depositions increased. The nanoparticles tend to grow forming agglomerates of a few thousand nanometers in size when more layers are deposited. SERS performance of the prepared SERS substrates was evaluated using p-aminobenzenethiol (PABT) as probe molecule reaching an estimated enhancement factor of 9.0 x1012. A novel and extremely low-cost surface-enhanced Raman spectroscopy substrate fabricated depositing gold nanoparticles on common lab filter paper using thermal inkjet technology is also reported. The paper-based substrate combines all advantages of other plasmonic structures fabricated by more elaborate techniques with the flexibility given by the inherent nature of the paper for efficient sample collection, robustness and stability. In this work the fabrication, characterization, and SERS activity of our substrate using 2,4,6-trinitrotoluene, 2,4- dinitrotoluene and 1,3,5-trinitrobenzene as analytes is described. The paper-based SERS substrates presented a high sensitivity and excellent reproducibility for analytes employed, demonstrating a direct application in forensic science and homeland security. The preparation of microporous nickel-oxalate metal organic framework (MOF), and its posterior deposition by ink-jet printing over a glass plate as an alternative for applications in gas sensing is also described. The synthesized MOF was characterized by XRD, TGA, IR and Raman spectroscopy, finding that this crystallizes in the space group P2/m. The prepared MOF film has the capacity to absorb small gaseous molecules such as NO2, a characteristic that can be exploited for gas sensing.