Resumen de Nanostructured micromaterials and devices for sensing and removing of chemical contaminants
This PhD thesis is related to the study and development of innovative nanostructured materials and devices join to strategies with interest for pollutants detection and removal being in line with the nowadays challenges of environmental technologies. The sensing and removing of chemical contaminants continues to be a research topic with an increasing interest for the scientific community. The development of novel nanostructured materials based on a CaCO3-polymer composite with different morphologies and polymorphs constitutes large part of this thesis. Material based on CaCO3-PEI from vaterite or calcite phase with spheric/ellipsoidic or rod shapes, respectively, have been synthesized. Several syntheses strategies modifying various reaction conditions were carried out up to finding of a new procedure, able to provide vaterite-PEI microspheres with controlled size and complete polymorph discrimination. In the new synthesis, CaCl2 and NaCO3 are mixing under 45 min of sonication, using 8 mg/mL poly(ethyleneimine) (PEI) as a crystal growth modifier (CGM) in the mixed water–organic solvent (H2O/EtOH). These hybrid nanostructured CaCO3(vaterite)-PEI material presents a high functionalizing capacity for biomolecules and an increase of the negative superficial charge. These properties make it suitable for electrochemical biosensor applications as demonstrated in collaborative works that appear in the annexes of this thesis. On the other hand, the reaction system to obtain the calcite-PEI microrods was found of special interest for the integration of sensing and removing processes achieving a dual “sensoremoval” actuation for contaminants within the same platform/system. This approach constitutes a proof-of-concept, that could lead to a next generation of environmental sensoremoval systems, giving new alternatives for environmental controlling and removing. The hybrid and nanostructured calcite-PEI particles in suspension permit the Pb2+ detection through a simple turbidimetric measurement, and at the same time act as heavy metal remover. This sensing and removing system is able to detect up to 1 ppm Pb2+ (being between 1 and 1000 ppm the lineal range) and reaches an adsorption capacity of 240 mg Pb2+/g calcite as evaluated at pH 4 after 30 min incubation time. The design and evaluation of highly sensitive paper based assay in format of lateral flow immunoassay for Cd2+ sensing in drinking waters has also been an important focus of the thesis. This topic constitutes one of the last trends in analytical chemistry. The device has a large response range being the linear response between 0.4 and 10 ppb. The quantification and detection limits of 0.4 and 0.1 ppb, respectively, represent the lowest ones reported so far for paper based metal sensors. In addition, a second integrated device that has an extra pad between the sample and conjugation pad with the adequate EDTA and ovalbumin concentrations for masking the metals interferences and allowing Cd2+ detection, was fabricated. Parts of the results presented in this PhD thesis have already been published or sent for publication beside being with interest for future industrial applications.
