Light-activated porphyrinoid-capped nanoparticles for gas sensing

The coupling of semiconductors with organic molecules results in a class of sensors whose chemoresistive properties are dictated by the nature of dyes. Organic molecules generally reduce conductivity, but in the case of optically active dyes, such as porphyrinoids, the conductivity is restored by illumination with visible light. In this paper, we investigated the gas sensing properties of ZnO nanoparticles coated with porphyrins and corroles. Under light illumination, the resistance of these materials increases with the adsorption of volatile compounds but decreases when these are strong electron donors. The behavior of these sensors can be explicated on the basis of the structural difference between free-base porphyrin and corrole, the influence of coordinated metal, and the corresponding electronic structures. These sensors are promising electronic noses that combine the selectivity to strong electron donors with the broad selectivity toward the other classes of chemicals. An efficient representation of the data of this peculiar array can be obtained by replacing the Euclidean distance with the angular distance. To this end, a recently introduced spherical principal component analysis algorithm is applied for the first time to gas sensor array data. Results show that a minimal gas sensor array (four elements) can produce a sort of chemotopic map, which enables us to cluster a very large class of pure chemical vapors. Furthermore, this map provides information about the composition of complex odor matrices, such as the headspaces of beef meat and their evolution over the time

Solar Cells

The second book of the four-volume edition of "Solar cells" is devoted to dye-sensitized solar cells (DSSCs), which are considered to be extremely promising because they are made of low-cost materials with simple inexpensive manufacturing procedures and can be engineered into flexible sheets. DSSCs are emerged as a truly new class of energy conversion devices, which are representatives of the third generation solar technology. Mechanism of conversion of solar energy into electricity in these devices is quite peculiar. The achieved energy conversion efficiency in DSSCs is low, however, it has improved quickly in the last years. It is believed that DSSCs are still at the start of their development stage and will take a worthy place in the large-scale production for the future

Photofunctional metal-organic framework thin films for sensing, catalysis and device fabrication

Metal Organic Frameworks (MOFs) constitute a developing class of materials constructed by metallic ions or inorganic clusters bridged by organic ligands, generating 2D or 3D extended porous crystalline structures. Their physical and chemical properties can be dramatically changed since the huge database of metal centers and type of ligands available for the design and construction MOFs. Besides, the implementation of anchored MOF onto different substrates opens up to an emerging field of device fabrication for specific applications. In this review we surveyed the recent progress and developments on MOF for sensing, catalylisis, photovoltaics, up conversion, and LED fabrication.Fil: Gomez, Germán Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Roncaroli, Federico. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Zinc Oxide Nanostructures: Synthesis and Characterization

The summary should be ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Zinc oxide (ZnO) is a wide band gap semiconductor with an energy gap of 3.37 eV at room temperature. It has been used considerably for its catalytic, electrical, optoelectronic, and photochemical properties. ZnO nanomaterials, such as quantum dots, nanorods, and nanowires, have been intensively investigated for their important properties. Many methods have been described in the literature for the production of ZnO nanostructures, such as laser ablation, hydrothermal methods, electrochemical deposition, sol-gel methods, chemical vapour deposition, molecular beam epitaxy, the common thermal evaporation method, and the soft chemical solution method. The present Special Issue is devoted to the synthesis and characterization of ZnO nanostructures with novel technological applications.

Modulation of Semiconductor Photoconversion with Surface Modification and Plasmon

Semiconductor devices are the basis of modern technology. Semiconductor-based photoconversion devices that convert light into electrical signals have shown potential for light energy harvesting and conversion, environmental remediation, and sensors for detection of light, chemicals, and biological substances. Despite this potential for use in many applications, semiconductor photoconversion devices need further improvement in the photoconversion performance. This photoconversion improvement may be manifested as increased photoconversion efficiencies for light harvesting devices for power generation such as photovoltaics and photoelectrochemical (PEC) cells or improved photoconversion modulation to increase the sensitivity of semiconductor photoconversion-based sensors. In addition, alternative semiconductor materials to semiconductors that utilize toxic heavy metals such as cadmium and lead must be found for use in certain semiconductor photoconversion devices. In this dissertation, three separate projects related to improving the performance of semiconductor photoconversion devices are presented. In the first project presented, a rutile titanium dioxide (TiO2) nanorod array photoanrode is coated with an ultra-thin porphyrin-based metal-organic framework (MOF) layer to improve the overall photoconversion of the photoelectrode for solar water splitting. The porphyrin-based MOF coated TiO2 nanorod array showed a 2.7x increase in photocurrent versus bare TiO2 nanorod arrays. The porphyrin-based MOF layer suppressed surface states on the rutile TiO2 nanorod array and increased charge separation and extraction from the rutile TiO2 due to the built-in electric field formed by a depleted p-n junction between the porphyrin-based MOF layer and the rutile TiO2 nanorods. In the second project presented, different plasmonic (hot electron injection and plasmon-induced resonant energy transfer (PIRET)) and non-plasmonic photoconversion enhancement mechanisms were tested for modulating photocurrent in PEC-based sensors using Bi3FeMo2O12 (BFMO) thin film semiconductor photoelectrodes and Hg2+ as a proof-of-concept analyte for detection. The possible plasmonic and non-plasmonic photoconversion enhancement mechanisms were controlled by choice of conjugated plasmonic nanoprobe between Au and Au@SiO2 core-shell nanoparticles with the BFMO. The conjugated Au NPs enhanced the BFMO thin film’s PEC performance through a combination of plasmonic hot electron injection, PIRET, Fermi-level equilibration, and a non-plasmonic internal reflection within the BFMO caused by the conjugated Au NPs. The conjugated Au@SiO2 NPs enhanced the BFMO thin film’s PEC performance via PIRET and the non-plasmonic internal reflection within the BFMO caused by the Au@SiO2 NPs. A PEC sensor using the Au NPs as nanoprobes showed sensitivity and selectivity towards Hg2+ showing this PEC sensor design’s potential. In the third project presented, based on the comparison study of plasmonic and non-plasmonic photoconversion enhancement mechanisms with BFMO thin-film photoanodes, a PEC-based immunosensor utilizing PIRET from Au NP-based nanoprobes conjugated to BFMO thin- film photoanodes to modulate photoconversion of the BFMO is synthesized and studied using human immunoglobulin G (IGG) as a proof-of-concept analyte. The plasmonic Au NPs are conjugated in the presence of human IGG via antibody-antigen reactions. The resulting PIRET-based PEC immunosensor shows some sensitivity towards IGG detection. However, the sensitivity of the PIRET-based PEC immunosensor is limited due to the large separation distance (~10 nm) between the plasmonic Au NPs the BFMO thin films from the antibody-antigen sandwich used for Au NP conjugation. As such, further work must focus on improving PIRET between the Au NP based nanoprobes and the BFMO thin film photoanodes

Carbon-Based Nanomaterials for (Bio)Sensors Development

Carbon-based nanomaterials have been increasingly used in sensors and biosensors design due to their advantageous intrinsic properties, which include, but are not limited to, high electrical and thermal conductivity, chemical stability, optical properties, large specific surface, biocompatibility, and easy functionalization. The most commonly applied carbonaceous nanomaterials are carbon nanotubes (single- or multi-walled nanotubes) and graphene, but promising data have been also reported for (bio)sensors based on carbon quantum dots and nanocomposites, among others. The incorporation of carbon-based nanomaterials, independent of the detection scheme and developed platform type (optical, chemical, and biological, etc.), has a major beneficial effect on the (bio)sensor sensitivity, specificity, and overall performance. As a consequence, carbon-based nanomaterials have been promoting a revolution in the field of (bio)sensors with the development of increasingly sensitive devices. This Special Issue presents original research data and review articles that focus on (experimental or theoretical) advances, challenges, and outlooks concerning the preparation, characterization, and application of carbon-based nanomaterials for (bio)sensor development

From nanoparticle networks to metal-organic frameworks: synthesis, structural engineering and applications

Nanoparticle networks, self-assembled from flame generated hot aerosols consisting of ceramic nanoparticles with well-controlled particle size, are promising materials for many different applications, especially for photodetectors and VOC sensors. Furthermore, the great structural flexibilities of these self-assembled nanoparticle networks including tuneable thickness and hierarchical porosity, precisely-controlled averaged particle size as well as chemical composition make them as potential platforms for templated materials synthesis via chemical conversion. On the other hand, metal-organic framework (MOF), is a growing family of microporous materials consisting of metal cations connected by organic linkers. Their unique properties, including a narrow pore size distribution (intrinsic porosity), designable topology, high accessible surface area, and chemical mutability, make MOFs promising materials for a variety of applications including gas storage, separation, catalysis, biotechnology, optics, microelectronics and energy production/storage. However, there are still several bottlenecks hindering the structural engineering of metal-organic frameworks, especially for pure crystalline MOF materials, including limited attainable thickness, scalability, poor mechanical stability (i.e. brittle nature of MOFs), hard to realize the morphological control (e.g. tuneable extrinsic hierarchical porosity) and geometric designs on pure crystalline MOF components. Thus, a facile synthetic approach for MOF structuring is highly desirable, which could afford the fabrication of three-dimensional MOF materials with possibly unlimited thickness, free-standing feature, the control over extrinsic hierarchy as well as pre-determined designs of MOFs while maintain their crystalline property and intrinsic extreme accessible surfaces. Firstly, we started with the synthesis of pure ZnO nanoparticle networks and the optimization of their particle size. Later, using the ZnO nanoparticle networks with an optimal particle size, a high-performing UV photodetector has been prepared to show a proof of concept application of such structural engineering. After achieving the first structural control over ZnO nanoparticle networks, a multi-dimensional control has been further investigated associated with its potential use for multi-functional devices including transparent conductive oxides and gas sensors. Given the successful structural control over nanoparticle networks, considering the existing bottlenecks in current MOF fabrication, this multi-dimensional structural control has been successfully replicated to MOF preparation via a means of gas phase conversion. Therefore, in this thesis, a systematic study has been presented from the synthesis and applications of nanoparticle networks to those of metal-organic frameworks in the sequence of: (i) the synthesis of three-dimensional nanoparticle networks (i.e. ZnO-based metal oxide nanoparticle networks), (ii) the realization of a precise particle size control over the synthesized nanoparticle networks (e.g. ZnO) and the use of resulted optimal structure for photodetector application, (iii) the realization of chemical composition manipulation over the synthesized nanoparticle networks (e.g. ZnO nanoparticle networks with varied Al doping concentrations) and the use of the resulted structures as proof of concept applications for both porous conductive electrodes and VOC sensor, (iv) the establishment of a synthetic pathway from nanoparticle networks to metal-organic frameworks based on the replication of the structural control over nanoparticle networks towards metal-organic frameworks, and the proof of concept application of the resulted free-standing metal-organic frameworks monolith for effective molecular sieve in batteries, and (v) the use of the established fabrication approach (i.e. from nanoparticle networks to metal-organic frameworks) for monolithic metal-organic framework patterning