Micro/nanomotors represent a burgeoning field of research featuring small devices capable of autonomous movement in liquid environments through catalytic reactions and/or external stimuli. This ...review delves into recent advancements in light-driven semiconductor-based micro/nanomotors (LDSM), focusing on optimized syntheses, enhanced motion mechanisms, and emerging applications in the environmental and biomedical domains. The survey commences with a theoretical introduction to micromotors and their propulsion mechanisms, followed by an exploration of commonly studied LDSM, emphasizing their advantages. Critical properties affecting propulsion, such as surface features, morphology, and size, are presented alongside discussions on external conditions related to light sources and intensity, which are crucial for optimizing the propulsion speed. Each property is accompanied by a theoretical background and conclusions drawn up to 2018. The review further investigates recent adaptations of LDSM, uncovering underlying mechanisms and associated benefits. A brief discussion is included on potential synergistic effects between different external conditions, aiming to enhance efficiency-a relatively underexplored topic. In conclusion, the review outlines emerging applications in biomedicine and environmental monitoring/remediation resulting from recent LDSM research, highlighting the growing significance of this field. The comprehensive exploration of LDSM advancements provides valuable insights for researchers and practitioners seeking to leverage these innovative micro/nanomotors in diverse applications.
The possibility of generating organically modified hollow TiO2 microspheres via a simple sol-gel synthesis was demonstrated for the first time in this work. A mixture of titania precursors, including ...an organically modified precursor, was used to obtain methyl-modified hollow TiO2 microspheres selective for bilirubin by the molecular imprinting technique (Methyl-HTM-MIM). Methyl-HTM-MIM were prepared by a sol-gel method using titanium (IV) isopropoxide (TTIP), and methyltitanium triisopropoxide (MTTIP) as precursors. Two ratios of titania precursors were tested (1/6 and 1/30 molMTTIP/molTTIP). With the characterization results obtained by the SEM and ATR-FTIR techniques, it was possible to establish that only the 1/30 molMTTIP/molTTIP ratio allowed for the preparation of hollow spheres with a reasonably homogeneous methylated-TiO2 shell. It was possible to obtain a certain degree of organization of the hybrid network, which increased with calcination temperatures. By adjusting isothermal adsorption models, imprinting parameters were determined, indicating that the new methylated microspheres presented greater selectivity for bilirubin than the totally inorganic hollow TiO2 microspheres. The effectiveness of the molecular imprinting technique was proven for the first time in an organically modified titania material, with imprinting factor values greater than 1.4, corresponding to a significant increase in the maximum adsorption capacity of the template represented by the molecularly imprinted microspheres. In summary, the results obtained with the new methyl-HTM-MIM open the possibility of exploring the application of these microspheres for selective sorption (separation or sensing, for example) or perhaps even for selective photocatalysis, particularly for the degradation of organic compounds.
Solid-phase microextraction commercial fibers present a few drawbacks such as relatively low recommended operating temperature, instability and swelling in organic solvents, breakage of the fiber, ...stripping of coatings, and bending of the needle. Some of these problems have been obviated by covalent bonding of the polymer phase to the fused-silica substrate by sol−gel, but the easy breakage of the fiber remains a problem. In the present work, the known occurrence of titanol groups at the surface of titanium wire was exploited to produce sol−gel fibers supported on this unbreakable substrate. Scanning electron microscopy analysis revealed the film formation on titanium wire surface while temperature and solvent stability as well as durability tests showed that the sol−gel film was tightly attached to the substrate, thus suggesting covalent bonding. The use of this type of fiber is currently generalized in our laboratory without any breakage or stripping out incidents up to the moment.
l-tyrosine controlled release systems, based on imprinted polymers radically polymerized in modified organic solvents (dimethyl sulfoxide and methanol) were developed. A set of copolymers synthesized ...with different functional monomers and the crosslinker ethylene glycol dimethylacrylate were evaluated regarding both the imprinting and controlled release features. Those prepared in modified-DMSO were mesoporous (surface area ranging 370–690 m2/g) but not the ones prepared in modified methanol with the exception of the imprinted polymer prepared with the monomer vinylbenzoic acid (209 m2/g). The swelling degree ranged 32 to 64% and appeared to be mostly dependent on the functional group employed in the synthesis of the polymers. When tested in dynamic mode a clear imprinting effect has been observed in some of the imprinted polymers. However, selectivity for l-Tyr against similar compounds could not be found in these conditions. Selectivity could be observed when carrying out the isothermal analysis, with selectivity factors up to 2.7. A few polymers exhibited also other remarkable features such as high l-Tyr load capacity (up to 253 mg l-Tyr/g) and large binding strength (up to 55 Lmmg(1-m))/g). Therefore, imprinted polymers capable of a selective sorption of l-Tyr upon equilibration, containing stronger binding sites for l-Tyr, appeared promising vehicles for its controlled release. In fact, the release assays with l-Tyr impregnation by adsorption, showed profiles corresponding to controlled release systems, with high yield (40–50%) and continuous release (up to at least 7 h). In addition, release mechanisms recommended for controlled release systems were deduced from kinetic data fitting to the Korsmeyer and Order 0 models.
Fucoidan, a sulfated polysaccharide extracted from brown seaweed, was, in the form of a silica composite, studied as a prospective cation imprinting matrix. The preparation of such composites in the ...presence of cations with a strong interaction with the biopolymer chains was expected to direct them towards arrangements, optimized for the sorption of those cations. As expected, the presence of Cu(II), a weakly fucoidan-binding cation, in the synthesis of the composites did not result in the production of significantly stronger Cu(II)-oriented binding arrangements, and therefore the imprinting was not successful. However, with Pb(II), with much stronger affinity for fucoidan, the materials obtained exhibited stronger (22%) binding as compared to the non-imprinted counterparts, and increased selectivity (1.4–1.6 fold) against Cd(II). Although these imprinting features were close to those observed previously with other sulfated polysaccharides, the fucoidan-based Pb(II) imprints developed here presented superior sorption properties, namely a higher capacity and higher binding strength for Pb(II). These features, demonstrated by the material developed here, may easily be put to work in different areas where Pb(II) sensing, determination, separation or remediation is of the utmost importance.
The possibility of generating organically modified hollow TiOsub.2 microspheres via a simple sol-gel synthesis was demonstrated for the first time in this work. A mixture of titania precursors, ...including an organically modified precursor, was used to obtain methyl-modified hollow TiOsub.2 microspheres selective for bilirubin by the molecular imprinting technique (Methyl-HTM-MIM). Methyl-HTM-MIM were prepared by a sol-gel method using titanium (IV) isopropoxide (TTIP), and methyltitanium triisopropoxide (MTTIP) as precursors. Two ratios of titania precursors were tested (1/6 and 1/30 molsub.MTTIP/molsub.TTIP). With the characterization results obtained by the SEM and ATR-FTIR techniques, it was possible to establish that only the 1/30 molsub.MTTIP/molsub.TTIP ratio allowed for the preparation of hollow spheres with a reasonably homogeneous methylated-TiOsub.2 shell. It was possible to obtain a certain degree of organization of the hybrid network, which increased with calcination temperatures. By adjusting isothermal adsorption models, imprinting parameters were determined, indicating that the new methylated microspheres presented greater selectivity for bilirubin than the totally inorganic hollow TiOsub.2 microspheres. The effectiveness of the molecular imprinting technique was proven for the first time in an organically modified titania material, with imprinting factor values greater than 1.4, corresponding to a significant increase in the maximum adsorption capacity of the template represented by the molecularly imprinted microspheres. In summary, the results obtained with the new methyl-HTM-MIM open the possibility of exploring the application of these microspheres for selective sorption (separation or sensing, for example) or perhaps even for selective photocatalysis, particularly for the degradation of organic compounds.
The possibility of generating organically modified hollow TiO
microspheres via a simple sol-gel synthesis was demonstrated for the first time in this work. A mixture of titania precursors, including ...an organically modified precursor, was used to obtain methyl-modified hollow TiO
microspheres selective for bilirubin by the molecular imprinting technique (Methyl-HTM-MIM). Methyl-HTM-MIM were prepared by a sol-gel method using titanium (IV) isopropoxide (TTIP), and methyltitanium triisopropoxide (MTTIP) as precursors. Two ratios of titania precursors were tested (1/6 and 1/30 mol
/mol
). With the characterization results obtained by the SEM and ATR-FTIR techniques, it was possible to establish that only the 1/30 mol
/mol
ratio allowed for the preparation of hollow spheres with a reasonably homogeneous methylated-TiO
shell. It was possible to obtain a certain degree of organization of the hybrid network, which increased with calcination temperatures. By adjusting isothermal adsorption models, imprinting parameters were determined, indicating that the new methylated microspheres presented greater selectivity for bilirubin than the totally inorganic hollow TiO
microspheres. The effectiveness of the molecular imprinting technique was proven for the first time in an organically modified titania material, with imprinting factor values greater than 1.4, corresponding to a significant increase in the maximum adsorption capacity of the template represented by the molecularly imprinted microspheres. In summary, the results obtained with the new methyl-HTM-MIM open the possibility of exploring the application of these microspheres for selective sorption (separation or sensing, for example) or perhaps even for selective photocatalysis, particularly for the degradation of organic compounds.
•CuBi catalysts with different Bi loadings were prepared and studied for the ERCO2.•A unique high selectivity for propane production was recorded (FE of 85.4 %).•Strong CO2 adsorption sites on the ...catalyst surface account for its catalytic behavior.•It is proposed that a bidentate carbonate is a key intermediate for ERCO2 to propane.
A series of CuBi catalysts were prepared with different Bi loadings and tested for the electrochemical reduction of CO2 (ERCO2). The developed catalysts were tested on a filter-press cell, and the influence of the catholyte on the catalytic performance was assessed. Catalyst #20C was found to be very selective for formate production, with a faradaic efficiency (FE) of 86.4 %, when Cl– ions are present in the catholyte solution. The presence of weak CO2 adsorption sites on the catalyst surface favors the formation of non-coordinated and monodentate carbonates after CO2 adsorption, resulting in enhanced formate formation through an outer-sphere mechanism. For catalyst #50C, an unprecedented propane selectivity was recorded (FE of 85.4%), being the first high-efficiency catalyst for the ERCO2 to propane ever reported. This remarkable catalytic behavior was attributed to strong CO2 adsorption sites on the catalyst surface and higher CO2 and CO adsorption capacity. It is also proposed that a bidentate carbonate is a key intermediate for the ERCO2 to propane, which is preferably formed when strong Lewis acid and base sites are present on the catalyst surface.
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