Microcantilever sensors for biochemical detection and analysis

Biochemical agents, including bacteria and toxins, are potentially dangerous and responsible for a wide variety of diseases. Reliable detection and characterization of small samples is necessary in order to reduce and eliminate their harmful consequences. Microcantilever sensors offer a potential alternative to the state of the art due to their small size, fast response time, and the ability to operate in air and liquid environments. At present, there are several technology limitations that inhibit application of microcantilever to biochemical detection and analysis, including difficulties in conducting temperature-sensitive experiments, material inadequacy resulting in insufficient cell capture, and poor selectivity of multiple analytes. This work aims to address several of these issues by introducing microcantilevers having integrated thermal functionality and by introducing nanocrystalline diamond as new material for microcantilevers. Microcantilevers are designed, fabricated, characterized, and used for capture and detection of cells and bacteria. The first microcantilever type described in this work is a silicon cantilever having highly uniform in-plane temperature distribution. The goal is to have 100 μm square uniformly heated area that can be used for thermal characterization of films as well as to conduct chemical reactions with small amounts of material. Fabricated cantilevers can reach above 300C while maintaining temperature uniformity of 2−4%. This is an improvement of over one order of magnitude over currently available cantilevers. The second microcantilever type is a doped single crystal silicon cantilever having a thin coating of ultrananocrystalline diamond (UNCD). The primary application of such a device is in biological testing, where diamond acts as a stable, electrically isolated reaction surface while silicon layer provides controlled heating with minimum variations in temperature. This work shows that composite cantilevers of this kind are an effective platform for temperature-sensitive biological experiments, such as heat lysing and polymerase chain reaction. The rapid heat-transfer of Si-UNCD cantilever compromised the membrane of NIH 3T3 fibroblast and lysed the cell nucleus within 30 seconds. Bacteria cells, Listeria monocytogenes V7, were shown to be captured with biotinylated heat-shock protein on UNCD surface and 90% of all viable cells exhibit membrane porosity due to high heat in 15 seconds. Lastly, a sensor made solely from UNCD diamond is fabricated with the intention of being used to detect the presence of biological species by means of an integrated piezoresistor or through frequency change monitoring. Since UNCD diamond has not been previously used in piezoresistive applications, temperature-denpendent piezoresistive coefficients and gage factors are determined first. The doped UNCD exhibits a significant piezoresistive effect with gauge factor of 7.53±0.32 and a piezoresistive coefficient of 8.12×10^−12 Pa^−1 at room temperature. The piezoresistive properties of UNCD are constant over the temperature range of 25−200C. 300 μm long cantilevers have the highest sensitivity of 0.186 m-Ohm/Ohm per μm of cantilever end deflection, which is approximately half that of similarly sized silicon cantilevers. UNCD cantilever arrays were fabricated consisting of four sixteen-cantilever arrays of length 20–90 μm in addition to an eight-cantilever array of length 120 μm. Laser doppler vibrometry (LDV) measured the cantilever resonant frequency, which ranged as 218 kHz−5.14 MHz in air and 73 kHz−3.68 MHz in water. The quality factor of the cantilever was 47−151 in air and 18−45 in water. The ability to measure frequencies of the cantilever arrays opens the possibility for detection of individual bacteria by monitoring frequency shift after cell capture.

Synteza, modyfikacja powierzchni i charakterystyka fizykochemiczna wielofunkcyjnych nanomateriałów luminescencyjnych zawierających jony pierwiastków ziem rzadkich

Wydział Chemii: Zakład Ziem Rzadkich

Role of Platinum Deposited on TiO2 in Photocatalytic Methanol Oxidation and Dehydrogenation Reactions

Titania modified nanoparticles have been prepared by the photodeposition method employing platinum particles on the commercially available titanium dioxide (Hombikat UV 100). The properties of the prepared photocatalysts were investigated by means of the Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-visible diffuse spectrophotometry (UV-Vis). XRD was employed to determine the crystallographic phase and particle size of both bare and platinised titanium dioxide. The results indicated that the particle size was decreased with the increasing of platinum loading. AFM analysis showed that one particle consists of about 9 to 11 crystals. UV-vis absorbance analysis showed that the absorption edge shifted to longer wavelength for 0.5% Pt loading compared with bare titanium dioxide. The photocatalytic activity of pure and Pt-loaded TiO2 was investigated employing the photocatalytic oxidation and dehydrogenation of methanol. The results of the photocatalytic activity indicate that the platinized titanium dioxide samples are always more active than the corresponding bare TiO2 for both methanol oxidation and dehydrogenation processes. The loading with various platinum amounts resulted in a significant improvement of the photocatalytic activity of TiO2. This beneficial effect was attributed to an increased separation of the photogenerated electron-hole charge carriers.

¿Cómo se mata a un amor, sin morir con El?

Como lectora, por segunda vez, de una de las novelas de María Bonilla tengo la oportunidad de compartir con los lectores de esta revista algunas reflexiones sobre mi lectura de su novela La actriz. ¿Qué es este cuadro dentro del cuadro, que nos introduce al libro mediante las paradojas del autoretrato? Una cierta manera de narrarse a sí misma, una autoficción que tiene como matriz de discurso la relación de esa autora consigo misma: una María Bonilla real con otra autora que narra su relación con una mujer de 41 o 42 años y que nos contará su íntima relación con el personaje de la reina de las hadas, Titania, de la obra de Shakespeare, El sueño de una noche de verano, escrita en 1596.

Highly dispersed Ptδ+ on TixCe(1−x)O2 as an active phase in preferential oxidation of CO

Structure–activity relationships for 1 wt.% Pt catalysts were investigated for a series of TixCe(1−x)O2 (x = 1, 0.98, 0.9, 0.5, 0.2 and 0) supports prepared by the sol–gel method. The catalysts prepared by impregnation were characterized in detail by applying a wide range of techniques as N2-isotherms, XRF, XRD, Raman, XPS, H2-TPR, Drifts, UV–vis, etc. and tested in the preferential oxidation of CO in the presence of H2. Also several reaction conditions were deeply analyzed. A strong correlation between catalyst performance and the electronic properties let us to propose, based in all the experimental results, a plausible reaction mechanism where several redox cycles are involved.

Hall Effect and transient surface photovoltage (SPV) study of Cu3BiS3 thin films

Se presentan las propiedades eléctricas del compuesto Cu3BiS3 depositado por co-evaporación. Este es un nuevo compuesto que puede tener propiedades adecuadas para ser utilizado como capa absorbente en celdas solares. Las muestras fueron caracterizadas a través de medidas de efecto Hall y fotovoltaje superficial transiente (SPV). A través de medidas de efecto Hall se encontró que la concentración de portadores de carga n es del orden de 1016 cm-3 independiente de la relación de masas de Cu/Bi. También se encontró que la movilidad de este compuesto (μ del orden de 4 cm2V -1s-1) varía de acuerdo con los mecanismos de transporte que la gobiernan en dependencia con la temperatura. A partir de las medidas de SPV se encontró alta densidad de defectos superficiales, defectos que son pasivados al superponer una capa buffer sobre el compuesto Cu3BiS3.

Photocatalytic production of chemicals and hydrogen from biomass

In this work, with the aim to tackle several approaches towards sustainable chemistry, two reactions were studied: aerobic photo-oxidation of biomass derived 5-hydroxymethyl-2-furfural (HMF), and anaerobic photo-reforming of glycerol known as a by-product in biodiesel industry, towards production of chemicals and hydrogen. Solar-assisted reactions were performed by means of heterogeneous photocatalysis, in mild conditions such as atmospheric pressure, room temperature and water as a benign solvent. Titanium dioxide (lab-synthesized and commercial) was used as a photo-active catalyst, which surface was modified by introducing different metal (e.g. Au, Au-Cu, Pt) and metal oxide (e.g. NiO) nanoparticles. The prepared materials were characterized by XRD, DRS, BET, TEM, SEM, RAMAN and other techniques. The influence of the support, the size and type of the deposited metal and metal oxide nanoparticles on the photo-catalytic transformation of HMF and glycerol was evaluated. In the case of HMF, the influence of the base addition and the oxygen content on the reaction selectivity was also studied. The effect of the crystalline phase composition and morphology of TiO2 in the glycerol photo-reforming reaction was assessed as well. The surface of the synthesized TiO2 nano-powders was investigated by means of Surface Organometallic Chemistry (SOMC) approach. In particular, the surface was characterized by chemical titration and DRIFT techniques. Furthermore, the SOMC concept allowed preparing of well-dispersed Pt nanoparticles on the TiO2 surface. The photo-catalytic activity of this sample in the glycerol photo-reforming process was tested and compared to that of other Pt-containing catalysts prepared by conventional technics. In view of avoiding the agglomeration and sedimentation of suspended titania powders in water media, thick films of synthesized and commercial TiO2 were deposited on a conductive substrate using screen-printing technique. The prepared electrodes were characterized by profilometry, SEM, XRD, optical, electrochemical and photo-electrochemical methods.

Peptidomimetic ligands for tuning integrin-mediated signalling: rational design, synthesis and theranostic applications

Integrins are α/β-heterodimeric transmembrane adhesion receptors that mediate cell-cell and cell-ECM interactions. Integrins are bidirectional signalling receptors that respond to external signals (“outside-in” signalling) and in parallel, transduce internal signals to the matrix (“inside-out” signalling), to regulate vital cellular functions including migration, survival, growth and differentiation. Therefore, dysregulation of these tightly regulated processes often results in uncontrolled integrin activation and abnormal tissue expression that is responsible for many diseases. Because of their important roles in physiological and pathological events, they represent a validated target for therapeutic and diagnostic purposes. The aim of the present Thesis was focused on the development of peptidic ligands for α4β1 and αvβ3 integrin subtypes, involved in inflammatory responses (leukocytes recruitment and extravasation) and cancer progression (angiogenesis, tumor growth, metastasis), respectively. Following the peptidomimetic strategy, we designed and synthesized a small library of linear and cyclic hybrid α/β-peptidomimetics based on the phenylureido-LDV scaffolds for the treatment of chronic inflammatory autoimmune diseases. In order to implement a fast and non-invasive diagnostic method for monitoring the course of the inflammatory processes, a flat glass-surface of dye-loaded Zeolite L-crystal nanoparticles was coated with bioactive α4β1-peptidomimetics to detect specific integrin-expressing cells as biomarkers of inflammatory diseases. Targeted drug delivery has been considered a promising alternative to overcome the pharmacokinetic limitations of conventional anticancer drugs. Thus, a novel Small-Molecule Drug Conjugate was synthesized by connecting the highly cytotoxic Cryptophycin to the tumor-targeting RGDfK-peptide through a protease-cleavable linker. Finally, in view to making the peptide synthesis more sustainable and greener, we developed an alternative method for peptide bonds formation employing solvent-free mechanochemistry and ultra-mild minimal solvent-grinding conditions in common, inexpensive laboratory equipment. To this purpose, standard amino acids, coupling agents and organic-green solvents were used in the presence of nanocrystalline hydroxyapatite as a reusable, bio-compatible inorganic basic catalyst.

Sviluppo di sistemi fotocatalitici per l'ossidazione selettiva di 5-idrossimetilfurfurale

Lo scopo di questo lavoro di tesi è stato lo studio dell’attività fotocatalitica nella reazione di ossidazione selettiva della 5-idrossimetilfurfurale (HMF) di diversi sistemi a base di diossido di titanio. Il lavoro ha comportato la preparazione di una polvere di ossido di titanio nanoparticellare tramite microemulsione. La polvere ottenuta è stata caratterizzata e confrontata con due polveri commerciali (Evonik P25 e Millenium DT51). Successivamente, la titania prepata tramite microemulsione è stata sottoposta a spray-freeze drying per aumentarne l’area superficiale e ridurne la densità. La tecnica di spray-freeze drying è stata poi utilizzata per sviluppare nanocompositi a base di titania, silice e ceria, e per decorare alcune polveri con nanoparticelle di oro e di oro/rame preformate. Le nanoparticelle sono state sintetizzate tramite un processo in acqua a basso impatto ambientale, usando un sistema glucosio-sodio idrossido come riducente e PVP come stabilizzante. Le polveri preparate sono state caratterizzate tramite analisi BET, DRS, XRD, SEM e TEM. Tutti i materiali sviluppati sono stati testati nella reazione di fotoossidazione selettiva dell’HMF utilizzando un simulatore solare. Sono inoltre state svolte prove fotocatalitiche utilizzando scavenger di specie attive, volte ad indagare il meccanismo promosso da alcune delle polveri preparate e le differenze fra questi.

Sviluppo e ingegnerizzazione di sistemi ibridi a base di nanoparticelle inorganiche e microalghe da applicare nella depurazione acque

Lo scopo di questo lavoro di tesi consiste nella produzione e ingegnerizzazione di nuovi sistemi ibridi ottenuti accoppiando nanoparticelle di titania con la microalga Chlorella Vulgaris, per applicazione nel settore del risanamento delle acque reflue. Lo studio è stato rivolto all’ottimizzazione del materiale, il quale integra due proprietà: l’attività fotocatalitica sfruttata per la degradazione degli inquinanti organici conferita dalla titania e la capacità di biosorbimento di metalli pesanti tipica della biomassa. I risultati hanno evidenziato effetti sinergici positivi promossi dalla dispersione della microalga sulla superficie dell’ossido ed in grado di migliorare le performance di biorimediazione del materiale. Al fine di favorire l’applicazione industriale del sistema catalitico preparato, i campioni prodotti in sospensione sono stati ingegnerizzati rimuovendo il solvente tramite tecnologia di Spray-Freeze-Drying. Con l’obiettivo di ottimizzare la formulazione e correlare le proprietà chimico-fisiche dei materiali alle performance ottenute, è stata svolta un’approfondita caratterizzazione sia sulle sospensioni (ELS, DLS) che sui prodotti granulati (BET, SEM-FEG, SEM-EDS). Le prestazioni funzionali dei campioni preparati sono state valutate rispetto alla reazione modello di fotodegradazione della Rodamina B e nell’assorbimento del catione rameico.

Solutions for the conservation and restoration of cement-based materials in XX Century architectural heritage

Among the most representative materials of XX Century architectural heritage, this dissertation focuses on the cement-based ones, investigating some different fields where they were exploited. Primarily, concerning the surface preservation of cement-based materials used with aesthetic intent, new self-cleaning treatments based on titania nanoparticles embedded in inorganic matrices were tested. In order to consider the role of porosity, the treatments were applied to different kinds of materials (cement-based mortar, marble and concrete) and several analyses were conducted to investigate the morphology of the coatings, their photocatalytic effectiveness, their durability and the interaction between the coating and the substrate material. The outcomes showed that several parameters influence the treatment’s performances, in particular, the presence and nature of the matrix, the concentration and dispersion of nanoparticles and, in some cases, the amount of substrate material which interacts with the coatings. Secondly, this dissertation deals with the historic “Terranova” render, a colored dry-mix mortar largely widespread in Europe in the first half of XX Century, whose formulation is still basically unknown. Some original samples of supposedly Terranova renders were subjected to several characterization analyses and the results were compared to those of the original “Terranova” render of the Engineering Faculty in Bologna. Despite the recurrence of some features, defining a common formulation seemed to be challenging. Finally, the repair and conservation of structural reinforced concrete in heritage buildings were investigated, adopting the former “Casa del Fascio” in Predappio (FC, Italy) as case study. Three different materials and solutions were tested on a slab of the building, making its repair only from the intrados. Then several analyses were conducted both on site and in laboratory. Aside from the specific features characterizing every product, the results highlighted that the application method played a fundamental role in the effectiveness of the retrofit strategies.

Multi-functional electrocatalysts for CO2 reduction reaction: towards the modulation of selectivity

The electrocatalytic reduction of CO2 (CO2RR) is a captivating strategy for the conversion of CO2 into fuels, to realize a carbon neutral circular economy. In the recent years, research has focused on the development of new materials and technology capable of capturing and converting CO2 into useful products. The main problem of CO2RR is given by its poor selectivity, which can lead to the formation of numerous reaction products, to the detriment of efficiencies. For this reason, the design of new electrocatalysts that selectively and efficiently reduce CO2 is a fundamental step for the future exploitation of this technology. Here we present a new class of electrocatalysts, designed with a modular approach, namely, deriving from the combination of different building blocks in a single nanostructure. With this approach it is possible to obtain materials with an innovative design and new functionalities, where the interconnections between the various components are essential to obtain a highly selective and efficient reduction of CO2, thus opening up new possibilities in the design of optimized electrocatalytic materials. By combining the unique physic-chemical properties of carbon nanostructures (CNS) with nanocrystalline metal oxides (MO), we were able to modulate the selectivity of CO2RR, with the production of formic acid and syngas at low overpotentials. The CNS have not only the task of stabilizing the MO nanoparticles, but the creation of an optimal interface between two nanostructures is able to improve the catalytic activity of the active phase of the material. While the presence of oxygen atoms in the MO creates defects that accelerate the reaction kinetics and stabilize certain reaction intermediates, selecting the reaction pathway. Finally, a part was dedicated to the study of the experimental parameters influencing the CO2RR, with the aim of improving the experimental setup in order to obtain commercial catalytic performances.