Colloidal inorganic nanocrystal based nanocomposites: Functional materials for micro and nanofabrication

The unique size- and shape-dependent electronic properties of nanocrystals (NCs) make them extremely attractive as novel structural building blocks for constructing a new generation of innovative materials and solid-state devices. Recent advances in material chemistry has allowed the synthesis of colloidal NCs with a wide range of compositions, with a precise control on size, shape and uniformity as well as specific surface chemistry. By incorporating such nanostructures in polymers, mesoscopic materials can be achieved and their properties engineered by choosing NCs differing in size and/or composition, properly tuning the interaction between NCs and surrounding environment. In this contribution, different approaches will be presented as effective opportunities for conveying colloidal NC properties to nanocomposite materials for micro and nanofabrication. Patterning of such nanocomposites either by conventional lithographic techniques and emerging patterning tools, such as ink jet printing and nanoimprint lithography, will be illustrated, pointing out their technological impact on developing new optoelectronic and sensing devices. © 2010 by the authors

UV and solar-based photocatalytic degradation of organic pollutants by nano-sized TiO2 grown on carbon nanotubes

Anew photocatalyst based on nano-sized TiO2 supported on single wall carbon nanotubes (SWCNTs) with tailored photocatalytic properties upon irradiation by both UV and solar simulated light was successfully employed for the degradation of a mixture of 22 organic pollutants in both ultrapure water and real secondary wastewater effluent. First-order degradation rates showed that under UV irradiation nanosized TiO2 supported on SWCNTs is much more effective than conventional Degussa P25 for degradation of iopamidol, iopromide, diatrizoic acid, diclofenac, triclosan and sulfamethoxazole in ultrapure water. For the remaining organics the degradation rates were comparable being in most of the cases Degussa P25 slightly more effective than nano-sized TiO2 supported on SWCNTs. Reactions performed in real secondary wastewater effluent showed a general reduction of degradation rates. Specifically, such a reduction was in the range 9-87% and 9-96% for the Degussa P25 and the nano-sized TiO2 supported on SWCNTs, respectively. Overall, the nano-sized TiO2 supported on SWCNTs under UV irradiation displayed comparable degradation rates with respect to convention Degussa P25. Under simulated solar irradiation the new prepared photocatalyst showed lower efficiency than Degussa P25 in ultrapure water. Such a gap was greatly reduced when the reactions were carried out in real secondary wastewater effluent. The nano-sized TiO2 supported on SWCNTs demonstrated to have the addition benefit to be easily removed from the aqueous solution by a mild centrifugation or a filtration step and, consequently, can be reused for a further photocatalytic treatment batch. Therefore, the obtained results showed that new photocatalyst based on nano-sized TiO2 supported on SWCNTs has proved to be a promising candidate to be used in a photocatalytic based-AOP and to be integrated with a biological step for the effective removal of emerging organic pollutants

Photocatalytic degradation of methyl-red by immobilised nanoparticles of TiO2 and ZnO

none6noIn this work, we report on the degradation of methyl-red (2-(4-Dimethylamino-phenylazo)-benzoic acid - C.I. 13020) under UV irradiation in the presence of nanosized ZnO and TiO2. Oxide nanocrystals with controlled size were synthesised by using non-hydrolytic approaches and tested for the photocatalysed degradation. The performances of the immobilised nanoparticles were compared with their commercial counterparts after immobilization onto a solid support. The influence of some experimental conditions, namely pH and dye concentration, were investigated by monitoring the dye decoloration spectrophotometrically. Several intermediate by-products were identified by HPLC-MS, showing that two different mechanisms were operative during the photocatalytic oxidationsee at: http://www.iwaponline.com/wst/04904/wst049040183.htmopenR. COMPARELLI; P. D. COZZOLI; M. L. CURRI; A. AGOSTIANO; G. MASCOLO; G. LOVECCHIOR., Comparelli; Cozzoli, Pantaleo Davide; M. L., Curri; A., Agostiano; G., Mascolo; G., Lovecchi

Opto‐Electronic Characterization of Photocatalysts Based on p,n‐Junction Ternary and Quaternary Mixed Oxides Semiconductors (Cu2O‐In2O3 and Cu2O‐In2O3‐TiO2)

Semiconductor materials are the basis of electronic devices employed in the communication and media industry. In the present work, we report the synthesis and characterization of mixed metal oxides (MOs) as p,n‐junction photocatalysts, and demonstrate the correlation between the preparation technique and the properties of the materials. Solid‐state UV-visible diffuse reflectance spectroscopy (UV‐VIS DRS) allowed for the determination of the light absorption properties and the optical energy gap. X‐ray photoelectron spectroscopy (XPS) allowed for the determination of the surface speciation and composition and for the determination of the valence band edge. The opto‐electronic behavior was evaluated measuring the photocurrent generated after absorption of chopped visible light in a 3‐electrode cell. Scanning electron microscopy (SEM) measurements allowed for auxiliary characterization of size and morphology, showing the formation of composites for the ternary Cu2O‐In2O3 p,n‐mixed oxide, and even more for the quaternary Cu2O‐In2O3‐TiO2 MO. Light absorption spectra and photocurrent‐time curves mainly depend upon the composition of MOs, while the optical energy gap and defective absorption tail are closely related to the preparation methodology, time and thermal treatment. Qualitative electronic band structures of semiconductors are also presented

Electrochemical Characterization and Electroanalytical Aplications of RGO_AuNPs Hybrids

A novel synthetic route for the synthesis of gold nanoparticles (AuNPs) modified graphene electrodes has been developed: Reduced Graphene Oxide (RGO) sheets are functionalized with pyrene linkers acting as growing sites for gold nanoparticles (AuNPs) of different dimensions (approximatively 5, 10 and 20 nm). The Au surface is functionalized with oleylamine or 3,4-dimethylbenzenethiol as capping agents. The hybrid material is deposited onto Carbon Screen Printed Electrodes (C-SPEs) for a deep physico-chemical and electrochemical characterization, using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. The role played by every single hybrid counterpart has been investigated, showing a synergistic effect, which is responsible of the enhancement of the system properties. The charge transfer from gold nanoparticles to graphene, assisted and stimulated by the pyrene linker, seems to be the key point to understand the peculiarities of this innovative material. The as prepared RGO-AuNPs hybrids have been used in the electroanalytical detection of both inorganic and organic species (arsenic, H2O2, dopamine), showing promising results in terms of sensitivities and detection limits. In particular, regarding the detection of the neurotransmitter dopamine by means of Differential Pulse Voltammetry in Phosphate Buffer Solution, a LOD of (3.3 \ub1 0.2) ppb has been reached, comparable with other electroanalytical results in the literature and in accordance with the benchmark for this molecule [1]. For arsenic detection, the hybrid devices show increased performances in comparison with bare gold or gold NPs, also allowing speciation between arsenic (III) and (V), appropriately adjusting the experimental conditions. In the case of H2O2, the hybrid devices display high electrocatalytic activity and fast electron-transfer kinetics, representing an ideal platform for developing oxidoreductase-based electrochemical biosensors as well as for detecting H2O2 in real samples. [1] J.A. Ribeiro, P.M.V. Fernandes, C.M. Pereira, F. Silva, Talanta 160 (2016) 653-679

High surface area mesoporous silica nanoparticles with tunable size in the sub-micrometer regime: Insights on the size and porosity control mechanisms

Mesoporous silica nanostructures (MSNs) attract high interest due to their unique and tunable physical chemical features, including high specific surface area and large pore volume, that hold a great potential in a variety of fields, i.e., adsorption, catalysis, and biomedicine. An essential feature for biomedical application of MSNs is limiting MSN size in the sub-micrometer regime to control uptake and cell viability. However, careful size tuning in such a regime remains still chal-lenging. We aim to tackling this issue by developing two synthetic procedures for MSN size mod-ulation, performed in homogenous aqueous/ethanol solution or two-phase aqueous/ethyl acetate system. Both approaches make use of tetraethyl orthosilicate as precursor, in the presence of cetyltri-methylammonium bromide, as structure-directing agent, and NaOH, as base-catalyst. NaOH catalyzed syntheses usually require high temperature (>80 °C) and large reaction medium volume to trigger MSN formation and limit aggregation. Here, a successful modulation of MSNs size from 40 up to 150 nm is demonstrated to be achieved by purposely balancing synthesis conditions, being able, in addition, to keep reaction temperature not higher than 50 °C (30 °C and 50 °C, respectively) and reaction mixture volume low. Through a comprehensive and in-depth systematic morphologi-cal and structural investigation, the mechanism and kinetics that sustain the control of MSNs size in such low dimensional regime are defined, highlighting that modulation of size and pores of the structures are mainly mediated by base concentration, reaction time and temperature and ageing, for the homogenous phase approach, and by temperature for the two-phase synthesis. Finally, an in vitro study is performed on bEnd.3 cells to investigate on the cytotoxicity of the MNSs

Social cognition in people with schizophrenia: A cluster-analytic approach

Background The study aimed to subtype patients with schizophrenia on the basis of social cognition (SC), and to identify cut-offs that best discriminate among subtypes in 809 out-patients recruited in the context of the Italian Network for Research on Psychoses. Method A two-step cluster analysis of The Awareness of Social Inference Test (TASIT), the Facial Emotion Identification Test and Mayer-Salovey-Caruso Emotional Intelligence Test scores was performed. Classification and regression tree analysis was used to identify the cut-offs of variables that best discriminated among clusters. Results We identified three clusters, characterized by unimpaired (42%), impaired (50.4%) and very impaired (7.5%) SC. Three theory-of-mind domains were more important for the cluster definition as compared with emotion perception and emotional intelligence. Patients more able to understand simple sarcasm (14 for TASIT-SS) were very likely to belong to the unimpaired SC cluster. Compared with patients in the impaired SC cluster, those in the very impaired SC cluster performed significantly worse in lie scenes (TASIT-LI <10), but not in simple sarcasm. Moreover, functioning, neurocognition, disorganization and SC had a linear relationship across the three clusters, while positive symptoms were significantly lower in patients with unimpaired SC as compared with patients with impaired and very impaired SC. On the other hand, negative symptoms were highest in patients with impaired levels of SC. Conclusions If replicated, the identification of such subtypes in clinical practice may help in tailoring rehabilitation efforts to the person's strengths to gain more benefit to the person

Low temperature synthesis of photocatalytic mesoporous tio2 nanomaterials

We report the synthesis of mesoporous TiO2 nanostructures based on the decomposition of TiOSO4 in aqueous alkaline solution at room temperature, followed by mild thermal treatment (110◦C) in an oven and suitable to yield up to 40 g of product per batch. The duration of the thermal treatment was found to be crucial to control crystalline phase composition, specific surface area, surface chemistry and, accordingly, the photocatalytic properties of the obtained TiO2 nanocrystals. The thorough investigation of the prepared samples allowed us to explain the relationship between the structure of the obtained nanoparticles and their photocatalytic behavior, that was tested in a model reaction. In addition, the advantage of the mild treatment against a harsher calcination at 450◦C was illustrated. The proposed approach represents a facile and sustainable route to promptly access an effective photocatalyst, thus holding a significant promise for the development of solutions suitable to real technological application in environmental depollution

TiO2 Nanocrystals Decorated CVD Graphene for Electroanalytical Sensing

In this work, the manufacturing and characterization of an optically transparent and UV-light photoactive anode, formed of monolayer graphene grown by chemical vapor deposition (CVD) and decorated with a close packed multilayered nanostructured layout of colloidal TiO2 nanocrystals (NCs), are reported. The hybrid material has been prepared by a facile solution-based procedure, which relays on soaking the CVD graphene in a solution of 1-pyrene butyric acid (PBA) surface coated TiO2 NCs, achieved upon implementation of a capping exchange process for displacing the pristine organic ligand deriving from the colloidal synthesis. Pyrene undergoes \u3c0-\u3c0 stacking interactions, anchoring the NCs to the platform with retention of the NC geometry and composition. The NCs immobilize onto the graphene platform with preservation of its aromatic structure and the resulting hybrid has been found optically transparent in the visible spectral range. (Photo)electrochemical investigation shows that the composite material has a promising sensitivity for selectively detecting dopamine and norepinephrine and, concomitantly, exhibits a (photo)electric activity higher than that of bare graphene. Thus, the achieved hybrid material results interesting for the manufacturing of photo-active components to integrate in photo-renewable sensor elements along with photodetectors and solar cells

Thermo-plasmonic killing of Escherichia coli TG1 bacteria

Plasmonic photo-thermal therapy (PPTT) is a minimally invasive, drug-free, therapy based on the properties of noble metal nanoparticles, able to convert a bio-transparent electromagnetic radiation into heat. PPTT has been used against cancer and other diseases. Herein, we demonstrate an antimicrobial methodology based on the properties of gold nanorods (GNRs). Under a resonant laser irradiation GNRs become highly efficient light to heat nano-converters extremely useful for PPTT applications. The concept here is to assess the antimicrobial effect of easy to synthesize, suitably purified, water-dispersible GNRs on Escherichia coli bacteria. A control on the GNRs concentration used for the process has been demonstrated critical in order to rule out cytotoxic effects on the cells, and still to be able to generate, under a near infrared illumination, an adequate amount of heat suited to increase the temperature up to ≈50 °C in about 5 min. Viability experiments evidenced that the proposed system accomplished a killing efficiency suitable to reducing the Escherichia coli population of about 2 log CFU (colony-forming unit)