Rosana Badía-Laíño

Role of surface adsorption and porosity features in the molecular recognition ability of imprinted sol-gels

Organically modified molecularly imprinted silicas (MIS) for nafcillin recognition were prepared using a simple sol-gel procedure. Molecular recognition of the template was observed by tuning the chemical and structural properties of the MIS. The relative amounts of organically modified alkoxysilane precursors were found to be key in the textural and morphological characteristics of the MIS as well as for developing an imprinting effect in the materials. The recognition properties of the imprinted materials were found to be strongly influenced by the hydrolytic stability of the alkoxysilanes and their inductive effects during sol-gel hydrolysis/condensation stages. The concept was to combine properties of organic groups with those of glass-like materials in order to develop synergetic properties through variations in the composition. Results from batch rebinding experiments as well as from the thorough study of the N(2) adsorption properties and the textural and structural characteristics of the MIS revealed that an imprint effect could be attributed to the presence of the template during the synthesis of MIS.

The Triplet State: Emerging Applications of Room Temperature Phosphorescence Spectroscopy

Abstract Room‐temperature phosphorescence (RTP) has been exploited for analytical research for over 30 years now due to the widespread recognition of its unique properties as a selective and sensitive technique, complementary to fluorescence. Recent years have seen the awakening of medical, geological, industrial, and technological interest in its application. The trend continues, driven by the achievements that have already been made and the promise of future achievements. This review attempts to cover specifically emerging applications of RTP in areas such as medicine, geological dating, forensics, and technology, illustrating the advantages that can be derived from the use of the technique and stressing its potential for novel applications.

Molecularly imprinted silica-silver nanowires for tryptophan recognition

We report on silver nanowires (AgNWs) coated with molecularly imprinted silica (MIP SiO2) for recognition of tryptophan (Trp). The use of AgNWs as a template confers an imprinted material with adequate mechanical strength and with a capability of recognizing Trp due to its nanomorphology when compared to spherical microparticles with a similar surface-to-volume ratio. Studies on adsorption isotherms showed the MIP-SiO2-AgNWs to exhibit homogeneous affinity sites with narrow affinity distribution. This suggests that the synthesized material behaves as a 1D nanomaterial with a large area and small thickness with very similar affinity sites. Trp release from MIP-SiO2-AgNWs was demonstrated to be dominated by the diffusion rate of Trp as controlled by the specific interactions with the imprinted silica shell. Considering these results and the lack of toxicity of silica sol-gel materials, the material offers potential in the field of drug or pharmaceutical controlled delivery, but also in optoelectronic devices, electrodes and sensors.

Engineered silica nanoparticles as additives in lubricant oils

Abstract Silica nanoparticles (SiO2 NPs) synthesized by the sol–gel approach were engineered for size and surface properties by grafting hydrophobic chains to prevent their aggregation and facilitate their contact with the phase boundary, thus improving their dispersibility in lubricant base oils. The surface modification was performed by covalent binding of long chain alkyl functionalities using lauric acid and decanoyl chloride to the SiO2 NP surface. The hybrid SiO2 NPs were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, simultaneous differential thermal analysis, nuclear magnetic resonance and dynamic light scattering, while their dispersion in two base oils was studied by static multiple light scattering at low (0.01% w/v) and high (0.50%w/v) concentrations. The nature of the functional layer and the functionalization degree seemed to be directly involved in the stability of the suspensions. The potential use of the functional SiO2 NPs as lubricant additives in base oils, specially designed for being used in hydraulic circuits, has been outlined by analyzing the tribological properties of the dispersions. The dendritic structure of the external layer played a key role in the tribological characteristics of the material by reducing the friction coefficient and wear. These nanoparticles reduce drastically the waste of energy in friction processes and are more environmentally friendly than other additives.

Unctuous ZrO2 nanoparticles with improved functional attributes as lubricant additives

One of the main drawbacks in the application of metal-oxide nanoparticles as lubricant additives is their poor stability in organic media, despite the good anti-wear, friction-reducing and high-load capacity properties described for these materials. In this work, we present a novel procedure to chemically cap the surface of ZrO2 nanoparticles (ZrO2NPs) with long hydrocarbon chains in order to obtain stable dispersions of ZrO2NPs in non-aqueous media without disrupting their attributes as lubricant additives. C-8, C-10 and C-16 saturated flexible chains were attached to the ZrO2NP surface and their physical and chemical characterization was performed by transmission electron microscopy, thermogravimetric analysis, attenuated total reflectance Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and solid-state nuclear magnetic resonance. The dispersion stability of the modified ZrO2NPs in non-aqueous media was studied using static multiple light scattering. Tribological tests demonstrated that dispersions of the long-chain capped ZrO2NPs in base lubricating oils exhibited low friction coefficients and improved the anti-wear properties of the base oil when compared with the raw lubricating oil.

Fluorescence | Fluorescence Derivatization

Fluorescence derivatization is a powerful tool for converting non- or weakly fluorescent analytes to highly fluorescent products through the specificity of chemical reactions. Many of the most established fluorescent derivatization reactions were developed for use to direct sensitive and selective determination of sample analytes such as metal ions, anions, bioactive compounds, drugs, pesticides, in addition to substances that tend to decompose during the analysis or for those substances that do not exhibit the desired properties for a given transduction method. Different chemical derivatization reactions are described as well as new reaction chemistries (click chemistry, bio-orthogonal) for derivatization of specific analytes in complex biological media without interfering with living systems. The broad array of fluorescence derivatization chemistries offer exceptional opportunities for practical applications in environmental science, medicine, pharmacy, analytical chemistry, optical sensing, bioimaging and cellular biology, fields dependent on selective and sensitive transduction techniques.

FLUORESCENCE | Fluorescence Labeling

The fluorescence labeling technology has opened new horizons in chemistry and biosciences, by turning nonluminescent or weakly luminescent molecules into highly fluorescent products. Fluorescence labeling, that can be achieved by covalent labeling, noncovalent binding, enzymatic reactions, metal complexation and other particular reactions, is a powerful tool for the analysis of a number of biomolecules and other solutes with high sensitivity and selectivity. Most of the methods developed for fluorescence labeling are based on the use organic fluorophores, metal centered dyes, molecular beacons, fluorescent proteins, among others. Besides, a novel family of fluorophores comprising luminescent nanoparticles provides several advantages over conventional labels, such as high quantum yield and less susceptibility to bleaching. In this article, the basic principles of different fluorescent labeling techniques relevant to chemistry and biology, their advantaged and drawbacks, are discussed.

FLUORESCENCE | Time-Resolved Fluorescence

Fluorimetry has experienced an explosive growth since the early 1980s, much of which has been driven by the use of fluorescence as a noninvasive technique for biology and biochemistry. Fluorescence techniques are widely used to quantify molecular parameters of different chemical, biochemical, and biological processes because of their inherent sensitivity, specificity and temporal resolution. In fact, the luminescence lifetime is an important characteristic of a fluorescent molecule and its environment. Many intra- and intermolecular processes are able to modulate the molecule emission which cannot be investigated by steady-state fluorescence measurements. For example, rotational diffusion, resonance-energy transfer, or dynamic quenching occur on the same timescale as the fluorescence decay. Lifetime measurements reveal dynamic information on the nanosecond timescale that is useful in fundamental studies of quenching and energy transfer and can be used in analytical methodologies to enhance selectivity and/or to perform multicomponent determinations. For example, fluorescence quenching may occur due to a ground state reaction or an excited state reaction. Only by measuring the fluorescence lifetime may one determine which process causes the quenching.