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Adsorption of organic compounds on microporus and nanostructured materials
No full textNegli ultimi anni, la comunità scientifica ha compiuto numerosi sforzi in settori di ricerca riguardanti i materiali nanostrutturati. Nella loro definizione più ampia, materiali con almeno una dimensione dell’ordine dei nanometri sono chiamati "Materiali Nanostrutturati" (MNs). Questa classificazione generale comprende realtà fisiche molto diverse tra loro, quali nanostrutture in forma di film sottili, nanoparticelle, materiali nanoporosi, nanocompositi e materiali nanocristallini, questi MNs sono di notevole interesse sia per la ricerca scientifica sia per applicazioni tecnologiche. In particolare, i Mns possiedono proprietà fisiche e chimiche che li rendono interessanti per lo sviluppo di dispositivi con elevata sensibilità, selettività ed efficienza. Infatti, essi sono caratterizzati da superfici superiori rispetto ai materiali convenzionali (ovvero presentano un gran numero di atomi o, più genericamente, specie chimiche in superficie, rispetto a materiali convenzionali, che consentono di ridurre l'energia libera del sistema attraverso legami chimici o interazioni fisiche con altre specie chimiche presenti nelle vicinanze). Queste superfici presentano proprietà uniche e notevolmente diverse da quelle dei materiali bulk e possono eventualmente acquisire, in scala nanometrica, caratteristiche dipendenti dalle dimensioni. Di conseguenza, i materiali nanoporosi e nanostrutturati risultano essere candidati ideali per interazioni di tipo superficie-intorno chimico, quali l'adsorbimento. Per questo motivo, lo studio dell’adsorbimento di materiali nanostrutturati è un'area di crescente importanza per poter comprendere, creare e migliorare i materiali per applicazioni tecnologiche nella produzione chimica, nel controllo ambientale, nel fotovoltaico e nei sistemi energetici. In questo lavoro abbiamo focalizzato la nostra attenzione sulle proprietà di adsorbimento dei materiali nanostrutturati appartenenti a due classi diverse, e precisamente le nanoparticelle ed i materiali nanoporosi. Entrambi presentano un'elevata superficie ottenuta, nel primo caso, fabbricando piccole particelle in cui il rapporto superficie-volume è elevato (nanoparticelle) e nel secondo caso, creando materiali nei quali la superficie vuota (cioè i pori) è elevata rispetto alla quantità di materiale bulk di supporto (nanoporosi). Lo scopo di questo studio è stata la valutazione delle prestazioni di questi materiali nanoadsorbenti per la loro applicabilità in tecnologie di bonifica delle acque naturali e come mezzo per processi di arricchimento in metodologie analitiche. Per quanto riguarda le nanoparticelle, sono state determinate le proprietà di adsorbimento/desorbimento di nanoparticelle d'oro nei confronti di nucleosidi e oligonucleotidi modificati per valutarne l’applicabilità nelle fasi di pre-concentrazione e/o
clean-up per l’analisi di campioni biologici complessi. In particolare, in questo lavoro, le nanoparticelle d’oro sono state impiegate per migliorare la sensibilità del metodo analitico micellar electrokinetic chromatography (MEKC). La pre-concentrazione basata sulla micro estrazione in fase solida (μSPE) con nanoparticelle d'oro è stata poi seguita da una preconcentrazione on-line del campione realizzata utilizzando la modalità reversed electrode polarity stacking mode (REPSM). Nelle condizioni ottimali, sono stati ottenuti fattori di arricchimento nel range da 360 a 400, i limiti di rilevabilità (LOD) con un rapporto segnale-rumore di 3 variavano da 2 a 5 nM ed i relativi recuperi di molecole biologiche da campioni acquosi sono stati dell’ordine del 95-103%. Il metodo proposto ha dimostrato elevati fattori di arricchimento, buona precisione e accuratezza in un breve tempo di analisi e, sulla base dei vantaggi di semplicità, elevata selettività e sensibilità e buona riproducibilità, può quindi avere un grande potenziale per applicazioni biochimiche. Inoltre, è stato studiato il comportamento diffusivo di addotti nanoparticelle-farmaco per l’importanza che questo fenomeno ha nello sviluppo di sistemi di drug delivery. Poiché gli analoghi dei nucleosidi presentano una potenziale attività antitumorale e/o antivirale, la loro solubilità ed il trasporto possono essere migliorati attraverso l’inclusione nelle cavità delle ciclodestrine. In questo contesto, si è studiata la possibilità di utilizzare nanoparticelle d’oro superficialmente modificate con ciclodestrine funzionalizzate -SH per l’adsorbimento di deossicitidina. Il processo di complessazione è stato caratterizzato sulla base dei coefficienti di diffusione del nucleoside e degli addotti da esso formati con le nanoparticelle d'oro derivatizzate, ottenuti mediante Taylor Dispersion Analysis. Questo studio ha permesso inoltre di determinare altri importanti grandezze utili a descrivere il sistema, quali ad esempio la frazione legata di molecola biologica all'interno delle ciclodestrine ed il raggio idrodinamico delle nanoparticelle. Per quel che riguarda i materiali nanoporosi ci siamo concentrati sulle proprietà adsorbenti di due zeoliti idrofobiche (ZSM-5 e zeolite Y) nei confronti di inquinanti organici per verificarne l’eventuale applicabilità nel campo delle tecnologie di bonifica delle acque. I Composti Organici Volatili (VOCs) sono sostanze inquinanti di particolare interesse a causa della loro frequente e diffusa presenza nelle acque naturali e della loro tossicità che può causare gravi rischi per la salute umana. Per questo motivo sono state proposte differenti tecnologie per la loro rimozione dall'ambiente e, tra queste, l’adsorbimento si è dimostrato essere una tecnica semplice, a basso costo ed efficace. Relativamente all’adsorbimento dei singoli inquinanti sulle zeoliti sono stati determinate le isoterme di adsorbimento, la cinetica e la termodinamica del processo e, per meglio descrivere il fenomeno, sono state ottenute informazioni anche sulle modificazioni
strutturali e sulla localizzazione delle molecole. Infine, è stata valutata l'efficienza di adsorbimento del materiale rigenerato dopo trattamento termico la quale ha dimostrato che le zeoliti possono essere riutilizzate per diversi cicli di adsorbimento con evidenti benefici sul costo e sulle prestazioni del processo. Generalmente gli inquinanti spesso coesistono in miscele nei comparti ambientali, per questo motivo è importante quantificare le interazioni competitive per prevedere la capacità di adsorbimento dei materiali nei confronti di miscele acquose complesse, che meglio simulano le condizioni riscontrate in natura. A basse concentrazioni (paragonabili a quelle generalmente riscontrate nelle acque superficiali), i fenomeni competitivi non dovrebbero giocare un ruolo significativo nel processo di adsorbimento, a causa dell’eccesso di siti di adsorbimento. Tuttavia, nel caso di un soluzioni altamente concentrate (sversamenti accidentali) o di esaurimento dell’adsorbente che si realizza ad esempio, durante il tempo di vita del materiale adsorbente, questi fenomeni competitivi possono rivestire un ruolo dominante. Analogamente a quanto fatto per i sistemi monocomponente, anche per le miscele binarie di inquinanti sono state determinate le prestazioni dei materiali nanoporosi mediante isoterme di adsorbimento competitivo ottenendo anche informazioni relativamente alla selettività zeolite. Il sistema miscela di inquinanti-zeolite è stato infine esaminato anche dal punto di vista strutturale per ottenere una migliore comprensione delle interazioni host-guest.In recent years, intensive scientific research efforts have been made in the areas of nanostructured materials. In their broadest definition, materials with a nanometer-sized microstructure are called “Nanostructured Materials” (NMs). This very general criterion actually includes very diverse physical situations, such as nanostructures in the form of thin films, nanoparticle, nanoporous materials, nanocomposites and bulk nanocrystalline materials and they are of interest both for basic scientific research and technological applications. In particular, these materials have a range of physical and chemical properties that make them fascinating for the development of devices with high sensitivity, selectivity and efficiency. In fact, nanostructures are characterized by higher surface areas than do conventional materials (it means that these materials exhibit a very large number of atoms, or chemical species in general, likely to reduce the free energy of the system that is inserted through chemical bonds or physical interactions with other chemical species present in their vicinity). These surfaces have generally unique properties which greatly differ from those of bulk materials and which may even acquire a characteristic size dependence at the nanometer scale. Consequently, nanoporous and nanostructured materials are ideal candidates for surface-environment interactions such as adsorption. For this reason, the study of the adsorption on nanostructured materials is an area of increasing importance to understanding, creating and improving materials for technological applications in chemical production, environmental control, photovoltaic and energy systems. In this work we have focused our attention on the adsorption properties of nanostructured materials belonging two different classes, namely nanoparticles and nanoporous materials. Both types of nanostructured materials present an high surface areas obtained either by fabricating small particles where the surface-to-volume ratio of the particles is high (nanoparticles) or by creating materials where the void surface area (pores) is high compared to the amount of bulk support material (nanoporous). Aim of this study is the evaluation of the performances of these nano-adsorbents for their applicability in remediation technologies of natural waters and as medium for enrichment step of analytical procedures. For that which concerns nanoparticles, the adsorption/desorption properties of gold nanoparticles towards labelled nucleosides and oligonucleotides were determined to examine their applicability in pre-concentration and/or clean-up step of analysis of biological complex samples. In particular, in this work, gold nanoparticles were employed to improve the sensitivity of the micellar electrokinetic chromatography (MEKC)
analytical method. The pre-concentration based on micro solid phase extraction (μSPE) with gold nanoparticles was followed by on-line sample pre-concentration realized by reversed electrode polarity stacking mode (REPSM). Under the optimum conditions, enrichment factors were obtained in the range from 360 to 400, the limits of detection (LODs) at a signal-to-noise ratio of 3 ranged from 2 to 5 nM and the relative recoveries of biological molecules from water samples were 95–103%. The proposed method provided high enrichment factors, good precision and accuracy with a short analysis time and, on the basis of the advantages of simplicity, high selectivity, high sensitivity and good reproducibility, the developed methodology may have great potential for biochemical applications. Furthermore, the diffusion behaviour of nanoparticles-drug adducts was investigated for its importance in the development of drug delivery systems. Because nucleoside analogues are potential anticancer and/or antiviral agents, their solubility and transport could be improved by inclusion inside the cyclodextrin cavity. In view of such kind of applications we investigated the ability of gold nanoparticles superficially modified with cyclodextin functionalized -SH to include the deoxycytidine. Complexation phenomena were detected by measuring the diffusion coefficients of the considered nucleoside and of its cyclodextrin-capped gold nanoparticles adducts. The diffusion coefficients of the single components and of the mixtures were estimated through Taylor Dispersion Analysis. This study allowed to determine others important parameters characterizing the system, such as the ligand fraction of the biological molecule inside the cyclodextrin cavity and the hydrodynamic radius of the nanoparticles. For that which concerns nanoporous materials we focused our attention on the adsorption properties of two hydrophobic zeolites (ZSM-5 and zeolite Y) towards organic pollutants for investigate their applicability in water remediation technologies. Volatile Organic Compounds (VOCs) are water pollutants of concerns, due to their frequent and widespread occurrence in natural water and their toxicity that can cause serious risk to human health. For this reason different remediation technologies have been proposed for their removal from the environment and, among them, adsorption was demonstrated to be a simple, low cost and effective technique. The adsorption isotherms, the kinetics and the thermodynamics of the adsorption process of single component pollutants onto the different zeolites have been determined. In order to better describe the phenomena also the framework structural modifications and the localization of the pollutant molecules were investigated. Finally, the adsorption efficiency of the regenerated material after the thermal treatment was evaluated. This study
demonstrated that zeolites can be re-used for various adsorption cycles with clear benefits on the cost and performance of the process. Generally multiple sorbates often coexist in the environment, for this reason quantifying competitive interactions is important to predict the adsorption capability of materials for complex aqueous mixtures. At low concentrations (usually found in surface waters), the competitive phenomena are not expected to be significant in the adsorption process. However, in the case of a highly concentrated solutions a full understanding of the competitive interactions among adsorbates would be necessary to predict adsorbent performances. Similarly to what made for single component, also for binary mixtures the adsorption performances of nanoporous materials were determined by competitive adsorption isotherms providing to the zeolite selectivity. The system pollutant mixturezeolite was finally examined by a structural determinations to get a better understanding of the host guest interactions
Determinazione mediante SPNE-MEKC di nucleosidi
No full textL'impiego di nanoparticelle d’oro (AuNPs) come mezzo adsorbente è una applicazione in rapida espansione a causa delle loro proprietà intrinseche che le rendono uno strumento molto promettente. A tal proposito, tali nanomateriali possono essere sintetizzati in una vasta gamma dimensionale (1-150 nm) con una limitata dispersione dimensionale, sulla loro superficie possono essere adsorbiti più agenti di targeting e/o terapeutici, infine il nucleo è atossico, biocompatibile e inerte [3].
Lo scopo del presente lavoro è stato quello di valutare l'interazione tra alcune molecole ad attività farmacologica, il cui interesse è dovuto alla loro attività farmacologica come farmaci antibiotici, antivirali e/o antitumorali, e le nanoparticelle d’oro (AuNPs) e di indagare l'applicabilità di queste NPs in sistemi di nano-estrazione in fase solida (Solid Phase Nano Extraction SPNE)
Probing gold nanoparticles/highly modified nucleosides interaction by capillary electrophoresis
No full textNanoparticles (NPs) are being employed in many different fields such as drug carriers, imaging agents
and analytical probes, due to their unique physico-chemical properties. With the growing of
nanotechnology applications in research and industry, the release of nanomaterials into the environment
could increase; therefore, ecotoxicological effects of NPs are rising concerns. Investigations on
molecule/nanoparticle interactions play a key role in both the determination of NP’s biocompatibility for
various biomedical applications and for nanosafety evaluation (1). Moreover, these studies can also find
application in sample pre-treatment and pre-concentration, in such cases NPs are employed as adsorbent
material (2). The aim of the present work was to evaluate the interaction between modified nucleosides
and gold nanoparticles (AuNPs), and to investigate the applicability of these NPs in Solid-Phase Nano-
Extraction (SPNE) systems.
The application of AuNPs as adsorbent media is a rapidly expanding application because their inherent
properties make them a very promising tool. In fact, controlled fabrication in a wide dimensional range
(1–150 nm) with limited size dispersity has been established. Moreover, AuNP surface can adsorb
multiple targeting agents and/or therapeutics. Finally, the core in essence is non-toxic, biocompatible and
inert (3). The nucleoside/AuNP system was studied by using Capillary Electrophoresis (CE), since it has
been demonstrated that this technique is a powerful tool to investigate bio-physical and kinetic parameters
of interactions between nanoparticles and compounds with biological activity (proteins, nucleotides,
DNA, drugs, etc. ...). In particular, we examined the effectiveness of CE in measuring the affinity
between AuNPs and three highly modified nucleosides (Figure 1): this class of compounds includes a
large number of molecules obtained from parent nucleosides. The increased interest in the synthesis of
new modified nucleosides is linked to their pharmacological activity as antibiotic, antiviral and/or antitumoral drugs. From the experimental data, the adsorption isotherm was calculated: AuNPs showed an high saturation
capacity for nucleoside C).
Release experiments were carried out by varying both the buffer composition and the surfactant
concentration of the medium. A recovery in the range 100-110% for different concentration levels of
nucleoside C) was obtained. Therefore, by employing AuNPs as adsorbent mean in Solid Phase Nano
Extraction (SPNE), an enrichment factor of 7 was attained. Finally, by combining SPNE with sample
injection in Reversed Electrode Polarity Stacking Mode (REPSM) which leads to a sample preconcentration
inside the capillary (4), an enrichment factor of about 50 was achieved. Furthermore,
AuNPs could be used in multiple adsorption/release experiments because, after total release of the
analyte, their adsorption capacity is fully maintained
Adsorption of 1,2-dichloroethane on ZSM-5 and desorption dynamics by in situ synchrotron powder X-ray diffraction
No full textThe adsorption/desorption behaviour of ZSM-5 loaded with 1,2-dichloroethane was studied using the in situ synchrotron X-ray powder-diffraction technique in the temperature range 30°–600 °C. Rietveld refinements allowed to monitor the DCE decomposition process as well as the structural modifications undergoing on ZSM-5 upon a temperature-programmed thermal treatment. These results clearly demonstrated that regeneration of ZSM-5 is effective when thermally treating the adsorbent at about 300 °C thus minimising the cost of the regeneration step of the adsorption process. Once regenerated and reloaded the Rietveld refinement indicates that both DCE location and content remain substantially unchanged thus confirming ZSM-5 is able to re-adsorb DCE in amounts comparable to that adsorbed in the first cycle, in very good agreement with the chromatographic results. In conclusion, the use of this adsorbent with unchanged adsorption performances after thermal regeneration under mild conditions appears very promising also over several cycles of the adsorption/desorption process
Hydrophobic zeolites as adsorbent media for pre-concentration of emerging contaminants in aqueous dilute solutions
No full textResearch is documenting with increasing frequency that many chemical compounds (pharmaceuticals, personal care products, flame retardants, etc.), that have not historically been considered as contaminants, are detected in natural waters in concentrations ranging from a few ng/L to a few μg/L: these are generally referred to as “contaminants of emerging concern” because the risk to human health and the environment may not be known. Conventional wastewaters and recycled water treatments are only partially effective in their removal or degradation, so they are continuously discharged into the environment [1].
Therefore, it is important to develop analytical methods able to detect these molecules in accurate way; sorption based technologies were demonstrated to be efficient and economical methods both for the removal of trace pollutants from water and for their enrichment. Among the large number of inorganic adsorbents, zeolites were proven to be efficient in the adsorption [2, 3] and the pre-concentration [4] of organic micropollutants from environmental matrixes.
The aim of the present work is to evaluate the application of hydrophobic zeolites (Beta and Y) as medium for solid phase extraction systems of pre-concentration, towards drugs in aqueous dilute solutions.
After adsorption experiments, the drug release has been evaluated by varying some parameters of the extracting phase like pH, ionic strength and organic modifier content. Since the drugs adsorption onto zeolites is driven by both hydrophobic and electrostatic interactions, satisfactory percentages of release have been obtained by employing aqueous extracting phases in a pH range in which electrostatic interactions are repulsive, thus limiting the use of organic solvents. Moreover, the zeolites can be completely regenerated after desorption of the analyte, without loss of adsorption efficiency: this allows their reuse, with a considerable saving of materials.
[1] Gros M., Petrović M., Ginebreda A., Barceló D.; Environment International 36 (2010) 15–26
[2] Martucci A., Pasti L., Marchetti N., Cavazzini A., Dondi F., Alberti A.; Microporous and Mesoporous Materials 148 (2012) 174–183
[3] Pasti L., Sarti E., Cavazzini A., Marchetti N., Dondi F., Martucci A., Journal of Separation Science (2013) 36, 1604–1611
[4] Costa A. A., Wilson W. B., Wang H., Campiglia A. D., Dias J. A., Dias S. C.L.; Microporous and Mesoporous Materials 149 (2012) 186–19
High Silica Zeolites for the Removal of Polar Organic Contaminants from Water
No full textEfficient methods for the removal of polar organic
contaminants, a contaminant class that includes many
pharmaceutically active compounds, is an emerging concern in the
production of safe water. Recent research publications show that
the very favorable adsorption kinetics along with the effective and
highly irreversible adsorption make high silica zeolites [1, 2],
cheap and environmental friendly materials, applicable for the
treatment of contaminated water. Here, we report on the adsorption
properties of organophilic synthetic zeolites differing in topology,
SiO2/Al2O3 ratio, channel systems and free window apertures with
respect to commonly used drugs. In particular, the interaction
between different drugs, such as ketoprofen, hydrochlorothiazide
and atenolol (ATN) and organophilic zeolites was systematically
investigated by considering the effect of surrounding pH, ionic
strength, and thus chemical state of drugs, in order to evaluate the
role of hydrophobic and electrostatic forces in the interaction
between the pharmaceutical molecule and the adsorbent
Adsorbimento di acido perfluoroottanoico su materiali mesoporosi
No full textL’acido perfluoroottanoico (PFOA) è un prodotto industriale utilizzato principalmente come intermedio, inoltre si può formare come sottoprodotto indesiderato di reazione in fase di produzione o di degradazione di sostanze perfluorurate. Il PFOA è una sostanza molto stabile chimicamente e può permanere inalterata se rilasciata nell’ambiente. La sua stabilità e la bassa tensione di vapore sono le proprietà chimico fisiche principali che la rendono classificabile come contaminante organico persistente. Questa tipologia di inquinante è inoltre caratterizzata da un’alta mobilità ambientale, infatti la particolare struttura molecolare con un gruppo idrofilo e uno lipofilo e la presenza del gruppo carbossilico rendono il destino ambientale del PFOA differente da quello dei composti organici persistenti. Gli studi sulla tossicità del PFOA su animali da laboratorio ne hanno evidenziato tossicità e effetti negativi sullo sviluppo (1). Il PFOA nell’ambiente si distribuisce preferenzialmente nel comparto acquatico, e date le sue caratteristiche di peristenza e tossicità costituisce un rischio per l’ecosistema e per la salute. Pertanto si sono studiate diverse metodologie per la sua rimozione dalle acque naturali, tra cui l’adsorbimento, che ha il vantaggio rispetto a processi ossidativi, di non formare sottoprodotti di degradazione. In questo lavoro, si sono studiate le proprietà adsorbenti di silici mesoporose ed in particolare di MCM-41 ed HMS nei confronti di PFOA in soluzioni acquose diluite. I risultati ottenuti hanno mostrato come questi materiali possono essere usati per rimuovere efficacemente il PFOA dalle acque. In particolare, l’applicazione di HMS sembra molto promettente. Questo materiale è caratterizzato dalla presenza di canali cilindrici interconnessi che gli conferiscono particolari proprietà desiderabili per l’adsorbimento in flusso quali una elevata capacità di adsorbimento e un buon trasferimento di massa. Inoltre la sintesi di HMS ha basso impatto ambientale in quanto avviene in fase idroalcolica a temperatura ambiente e al contrario della MCM-41 non richiede condizioni di elevata temperatura e pressione e neppure l’impiego di soluzioni alcaline corrosive. Infine, la rimozione del templante dall’HMS può essere condotta a basse temperatura impiegando alcoli o soluzioni acquose anzichè ricorrere a processi di calcinazione ad alte temperature. Le caratteristiche sopra descritte rendono quindi questo materiale, ‘green’ e compatibile con l’ambiente, particolarmente adatto a metodologie di bonifica ambientale
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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