Browsing by Subject "Raman spectroscopy"

Now showing 1 - 4 of 4
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    Exploring the structure andelectronic properties of individual hybrid GO/rGOflakes
    Navarro-Rodriguez, Mario; Camus, Victor; Cros, Ana; Garro, Nuria; Somoza, Andres M.; Palacios-Lidon, Elisa; Física
    Despite its great potential, the use of graphene oxide (GO) in sensors, photocatalysis, or biomedicine applications is limited by its low conductivity. This drawback is typically overcome by using its reduced form (rGO) albeit sacrificing some of its extensive chemical properties. In this study, we unveil a nonuniform reduction process that enables the fabrication of hybrid flakes consisting of both size tunable GO and rGO regions. The nanoscale resolution of Kelvin probe force microscopy together with co-localized Raman spectroscopy allow us to correlate the local reduction degree with the nanoscale electronic properties, chemical composition, and structural defects. Additionally, we introduce a reliable metric for quantifying the extent of reduction. This research opens up possibilities for the development of new 2D nanohybrid materials that combine the high reactivity of GO and the enhanced conductivity of rGO, enabling applications in selective functionalization.
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    High-repetition-rate femtosecond laser processing of acrylic intra-ocular lenses
    (MDPI AG, 2020-01-20) Sola, Daniel; Cases, Rafael; Física
    The study of laser processing of acrylic intra-ocular lenses (IOL) by using femtosecond laser pulses delivered at high-repetition rate is presented in this work. An ultra-compact air-cooled femtosecond diode laser (HighQ2-SHG, Spectra-Physics) delivering 250 fs laser pulses at the fixed wavelength of 520 nm with a repetition rate of 63 MHz was used to process the samples. Laser inscription of linear periodic patterns on the surface and inside the acrylic substrates was studied as a function of the processing parameters as well as the optical absorption characteristics of the sample. Scanning Electron Microscopy (SEM) Energy Dispersive X-ray Spectroscopy (EDX), and micro-Raman Spectroscopy were used to evaluate the compositional and microstructural changes induced by the laser radiation in the processed areas. Diractive characterization was used to assess 1st-order efficiency and the refractive index change.
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    Human root dentin microhardness and degradation by triple antibiotic paste and calcium hydroxide
    (2022) Guzmán, Sonia; Caccia, Mario; Cortés, Olga; Bolarían, José M.; Requena, Alberto; García-Godoy, Alexander; Boj, Juan R.; García-Godoy, Franklin; Dermatología, Estomatología, Radiología y Medicina Física
    Purpose: To investigate and compare the effects of the two widely used regenerative endodontics medicaments: Triple antibiotic paste (ciprofloxacine-metronidazole-clindamycin) and calcium hydroxide on the microhardness and degradation of human root dentin. Methods: Following ethical approval and subject consent to use teeth in this research study, 60 singled-rooted permanent human teeth were randomly divided into six groups:(1) Tri-antibiotic paste with distilled water, or with (2) propylene glycol, (3) calcium hydroxide with distilled water, (4) calcium hydroxide propylene glycol, (5) untreated extracted teeth as negative controls, or (6) teeth instrumented and filled with calcium hydroxide or tri-antibiotic paste as positive controls. The microhardness tests were conducted after 1 and 2 months of exposure to the medicaments using a Vickers microhardness tester. Raman spectroscopy and energy dispersive x-ray spectroscopy were used to evaluate the chemistry and structure of the root dentin. Results: There were differences in the dentin microhardness following treatment with the medicaments or controls (P< 0.05). The time of root dentin exposure to the medicaments was similar (P> 0.05). The root dentin microhardness was lower in the teeth treated with the triple antibiotic paste or calcium hydroxide when combined with propylene glycol. The root dentin collagen in these treated teeth were also significantly degraded when viewed with Raman spectroscopy and energy dispersive x-ray spectroscopy, whereas the inorganic phase (dentin) remained unaltered. Samples exposed to the antimicrobial agents with water as a vehicle exhibited stronger microhardness and less degradation.
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    Raman spectroscopic strategy for the discrimination of recycled polyethylene terephthalate in water bottles
    (Wiley, 2022-10-03) Peñalver, Rosa; Arroyo-Manzanares, Natalia; López-García, Ignacio; Viñas, Pilar; Zapata Arráez, Félix; Química Analítica
    A reliable and quick strategy for the discrimination between recycled and virgin polyethylene terephthalate water bottles was developed by applying Raman spectroscopy combined with chemometrics. Chemometric models were created by orthogonal partial least square discriminate analysis (OPLS-DA) using the Raman spectra dataset in the range of 600–1800 cm-1. The Pareto scale model allowed the classification of virgin and recycled terephthalate of polyethylene (PET) samples with a percentage of success of about 95%. In addition, PLS regression was carried out to determine the level of recycled material in the PET water bottles with a good fit (R2 = 0.8920). This analytical approach shows a quick, accurate, and robust way to detect and quantify the adulteration of plastic bottles with recycled plastic materials to avoid fraud in the recycling plastic area.