1,721,008 research outputs found
Self-cleaning features of an innovative engineered sensor based on silica, silver nanoparticles and titania
No full textPassivation of the electrode surface and fouling are important challenges in electroanalysis during the use of modified electrodes in complex matrices, especially in the biomedical and environmental fields [1-2].
In order to overcome such problems, the production of highly engineered ad hoc designed devices could access really effective sensors [2]. In particular, a performing, reliable and reusable sensor, that could be cleaned by a simple irradiation with UV or solar light, would be perfect for this purpose.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer was developed [3-4]. Such structure confers to the device multifunctional properties for a complex biomedical challenge: the detection and quantification of catecholamine neurotransmitters. The sensor was thoroughly investigated by structural, morphological and electrochemical characterizations in order to understand the role of each component with the aim to improve the robustness and efficiency of the electroanalytical system.
The overlayer was made of anatase (the active polymorph of titanium dioxide) as confirmed by X-ray diffraction and by measuring the photodegradation of model contaminants. The size distribution of silver nanoparticles, the device architecture and surface homogeneity were inspected by electron microscopy. Electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that a highly ordered distribution of silver nanoparticles constitutes the active core of the device, allowing easier electron transfer and better quantification of the analytes even in the presence of conventional interferents, e.g. ascorbic and uric acid. Titania photoactive top layer allowed total recovery of the device performance in terms of sensitivity after a fast and simple UV-A cleaning step, affordable with different UV sources. This self-cleaning property, combined with a remarkable resistance against aging and ease of use, allows to employ the sensor also in on-field and remote applications.
References
1. C.M.A. Brett, Pure Appl. Chem. 73, 2001, pp 1969–1977.
2. C.M. Welch, R.G. Compton, Anal. Bioanal. Chem. 384, 2006, pp 601–619.
3. G. Maino, D. Meroni, V. Pifferi, L. Falciola, G. Soliveri, G. Cappelletti, S. Ardizzone, J. Nanoparticle Res. 15, 2013, pp 2087.
4. G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst 140, 2015, 1486-1494
PTFE-based core-shell nanoparticles preparation and characterization: a route towards the assembly of ordered soft-matter layers with tuneable (photonic) properties
No full textThe assembly of ordered arrangements of nanoparticles can represent a route towards the preparation of materials with innovative physical properties stemming from the characteristics of the nanoparticles themselves and from the controlled interactions amongst them.
Composite materials could exhibit interesting photonic properties if different components are spaced regularly in its bulk: the controlled 2D or 3D assembly of core-shell polymer nanoparticles results in such a regular spacing of the core material. The possibility of controlling the size of the core and the thickness of the shell represents a viable route towards the design of photonic properties towards the realization of nanostructured polymer opals.
PTFE latexes can be obtained with a narrow nanoparticle size distribution. Around such seeds, we could grow shells made of different types of polymers or copolymers that will quantitatively coat the dispersed PTFE seeds. A control of the shell thickness can be obtained by varying the ratio between seed and shell monomer(s). A careful choice of monomers can lead to water-soluble core-shell nanoparticles with markedly different properties. For instance the shell can swell in water (and respond to pH changes) or, alternatively be quite rigid and insensitive to the environment. The comonomers mix will lead to shells with markedly different thermal properties.
In this communication, we report our success in preparing and characterizing a variety of different PTFE-based core-shell systems with shells made with comonomers mixtures such as methylacrylate, ethylacrylate and methacrilic acid, or butylacrylate and methacrilic acid, or simply with methylmethacrylate. Such core-shell nanoparticles have been then used to make ordered layers that have been characterized by atomic force microscopy.
The success in the preparation of these core-shell systems might lead to materials that could exhibit the valuable properties of PTFE while reducing some of its disadvantages, such as its compatibility with other materials (adhesion and wettability). In the near future we will be investigating the possible applications and photonic properties of such regularly arrange nanoparticulate systems
PTFE-based core-shell nanoparticles: a possible way towards the assembly of ordered soft-matter layers with tuneable (photonic) properties
No full textThe assembly of ordered arrangements of nanoparticles can represent a route towards the preparation of materials with innovative physical properties stemming from the characteristics of the nanoparticles themselves and from the controlled interactions amongst them.
Composite materials could exhibit interesting photonic properties if different components are spaced regularly in its bulk: the controlled 2D or 3D assembly of core-shell polymer nanoparticles results in such a regular spacing of the core material. The possibility of controlling the size of the core and the thickness of the shell represents a viable route towards the design of photonic properties towards the realization of nanostructured polymer opals.
PTFE latexes can be obtained with a narrow nanoparticle size distribution. Around such seeds, we could grow shells made of different types of polymers or copolymers that will quantitatively coat the dispersed PTFE seeds. A control of the shell thickness can be obtained by varying the ratio between seed and shell monomer(s). A careful choice of monomers can lead to water-soluble core-shell nanoparticles with markedly different properties. For instance the shell can swell in water (and respond to pH changes) or, alternatively be quite rigid and insensitive to the environment. The comonomers mix will lead to shells with markedly different thermal properties.
In this communication, we report our success in preparing and characterizing a variety of different PTFE-based core-shell systems with shells made with comonomers mixtures such as methylacrylate, ethylacrylate and methacrilic acid, or butylacrylate and methacrilic acid, or simply with methylmethacrylate [1,2]. Such core-shell nanoparticles have been then used to make ordered layers that have been characterized by atomic force microscopy [3].
The success in the preparation of these core-shell systems might lead to materials that could exhibit the valuable properties of PTFE while reducing some of its disadvantages, such as its compatibility with other materials (adhesion and wettability). In the near future we will be investigating the possible applications and photonic properties of such regularly arrange nanoparticulate systems
Preparation and optical properties of artificial opals by self-assembly of PTFE-based core-shell nanoparticles
No full textGoing 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
Patterning of polymer brushes made easy using titanium dioxide: direct and remote photocatalytic lithography
Full text linkPhotocatalytic lithography is proved for the realization of micropatterned polymer brushes. Initiator-functionalized titanium dioxide or silicon surfaces are respectively exposed directly to near-UV light through a photomask (direct approach) or through a transparent photoactive TiO2 film (remote approach). Initiator patterns are then amplified as polymer brushes with SI-ATRP. Features down to 10 μm could be obtained using simple equipment. The process is intrinsically parallel, has high throughput and scalable to wafer size, making it powerful for microfabrication purposes
The power of three: Silica-Silver-Titania engineered sensors bearing photocatalytic self-cleaning features
No full textFouling and passivation are the main challenges faced during electroanalysis of complex matrices, especially those commonly encountered in the biomedical and environmental fields [1]. The production of highly engineered devices, designed ad hoc for specific applications, is the key factor in the direction of overcoming such problems and accessing effective sensors. A performant, reliable and reusable sensor, that could be cleaned simply by irradiation with UV light, would perfectly match this goal.
We designed a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer [2, 3]. Such structure equips the device with multifunctional properties for a complex biomedical challenge: the detection and quantification of catecholamine neurotransmitters. The crucial importance of each component to make our device a robust and efficient electroanalytical system was thoroughly investigated. The size distribution of silver nanoparticles, the device architecture and surface homogeneity were inspected by electron microscopy. The overlayer was made of anatase (the active polymorph of titanium dioxide) as confirmed by X-ray diffraction and by measuring the photodegradation of model contaminants. Electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that an highly ordered distribution of silver nanoparticles is the active core of the device, allowing easier electron transfer and better quantification of the analytes even in the presence of typical interferents, e.g. ascorbic acid and uric acid.
The high photoactivity of titania top layer allowed total recovery of the device performance in terms of sensitivity after a fast UV-A cleaning step. This self-cleaning property, combined with a remarkable resistance against aging, make our sensor also suitable for on-field applications
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