61 research outputs found
Second-Generation Tris(2-pyridylmethyl)amine–Zinc Complexes as Probes for Enantiomeric Excess Determination of Amino Acids
No full textSelf-assembly through imine condensation chemistry in combination with metal coordination is becoming one of the leading strategies for the preparation of stereodynamic probes for the determination of enantiomeric excess. Recently, we reported a novel molecular architecture based on a modified tris(2-pyridylmethyl)amine–zinc(II) complex [TPMA = tris(2-pyridylmethyl)amine] that is able to function as an optical probe for the determination of the enantiomeric excess of amino acids. Herein, we report on how a slight modification of the TPMA ligand enhances both the dichroic response and the stability of the system. The novel probe provides a much higher dichroic signal compared with the previously reported system
Triggering Assembly and Disassembly of a Supramolecular Cage
No full textA novel supramolecular cage built from the self-assembly of tris(2-pyridylmethyl)amine zinc complexes through imine condensation chemistry is reported. The cage recognition properties over a variety of structurally related guests, together with the kinetic study of the template assembly and disassembly, have been investigated in detail. This knowledge has been used to selectively modulate the rate of both assembly and disassembly processes. In particular, a novel disassembly method induced by strain release of the guest has been developed
Photoinduced hydrogen evolution with new tetradentate cobalt(ii) complexes based on the TPMA ligand
No full textHydrogen production from water splitting is nowadays recognized as a target, fundamental reaction for the production of clean fuels. Indeed, tremendous efforts have been devoted towards the research of suitable catalysts capable of performing this reaction. With respect to heterogeneous systems, molecular catalysts such as metal complexes are amenable to chemical functionalization in order to fine tune the catalytic properties. In this paper a new class of tris(2-pyridylmethyl)-amine (TPMA) cobalt(ii) complexes (CoL0-4) has been synthesized and employed as hydrogen evolving catalysts under photochemical conditions taking advantage of Ru(bpy)32+(where bpy is 2,2′-bipyridine) as a light-harvesting sensitizer and ascorbic acid as a sacrificial electron donor. Tuning of the photocatalytic activity has been attempted through the introduction of different substituents at the catalyst periphery rather than through a direct chemical modification of the chelating TPMA ligand. The results show that CoL0-4 behave as competent hydrogen evolving catalysts (HECs), although the effects played by the different substituents on the catalysis are relatively modest. Possible reasons supporting the observed behavior as well as possible improvements of the aforementioned tuning approach are discussed
Determination of Amino Acid Enantiopurity and Absolute Configuration: Synergism between Configurationally Labile Metal-Based Receptors and Dynamic Covalent Interactions
No full textReliable determination of the enantiomeric excess of free amino acids can be obtained by measuring the induced circular dichroism of a multicomponent assembly formed by a modified tris(2-pyridylmethyl)amine ligand, a zinc salt, and the amino acid of interest. The systems furnish reliable information for all natural amino acids. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
From single to multiple TiO2 nanotubes layers: Analysis of the parameters which influence the growth
No full textHighly-ordered vertically oriented TiO2 nanotube arrays (TiO2 NTs) are widely exploited in many different fields such as catalysis, electronics and biomedicine. TiO2 NTs can be synthetized by a number of methods; however, the synthesis via anodization in a fluoride-based electrolyte, proposed for the first time in 2001, has been proved to be the procedure which offers the best control over the nanotube dimensions. In literature, four generations of TiO2 NTs obtained with different types of anodization baths have been reported, each bath giving rise to TiO2 NTs with specific morphological features. In this work, we performed the growth of third generation TiO2 NTs by varying different parameters (i.e. voltage, temperature, anodization time, bath composition) and systematically analyzed their influence on NTs morphology. A deep knowledge of the effect of each parameter allowed their suitable combination in order to obtain double and triple NTs layers with different length and aspect ratio. The proposed method can be applied to synthetize multiple layers with predictable and well-defined features
Internalisation of core-shell superparamagnetic nanoparticles into human granulocytes
No full textIn this paper, multitasking core-shell Fe3O4@Cu@Au
superparamagnetic nanoparticles (MNPs) functionalised either with folic
acid (FA) or methotrexate (MTX) have been used for engulfment of human
granulocytes. MNPs internalisation into phagocytes allows to use the cells as
carriers thus avoiding the rapid clearance and decreasing of concentration
commonly experienced in case of in vivo nanoparticles administration.
MNPs have been coated with poly-L-lysine (PLL), which contributes to
improve their dispersion into polar solvents. Moreover, this coating improves
the cellular uptake and allows the further functionalisation with MTX and FA.
Experimental evidences of granulocytes engulfment have been obtained by
both SEM and fluorescence microscopy, upon prior labelling of the lysines
residues with suitable fluorescent probes. The superparamagnetic nature of the
MNPs makes the system easily drivable into a specific tissue upon exposure to
a defined magnetic field. The success of the internalisation experiments
indicates that the system is a promising tool as theranostic agent for treatment
of a variety of diseases, including tumours
Stimuli-responsive monolayers
No full textThe use of self-assembled monolayers (SAMs) for the functionalization of surfaces is extremely widespread among the scientific community, because they are easy to prepare and thermodynamically stable. Inferior binding uniformity, packing density, and molecular alignment have recently been observed also for SAMs made of thioether-based tripodal ligands with respect to the corresponding SAMs made of thiol-based tripodal ligands. This chapter presents an overview of the literature on smart mono-layers which respond to different stimuli both for their characterization and for their interaction with other molecules. It talks about mono-layers such as light-responsive, temperature-responsive, ph-responsive, electrochemically responsive and multi-responsive monolayers in detail. The examples described in the chapter show the high importance of smart SAMs for surface characterization, postimmobilization monitoring, and switching processes
Rice Husk Waste-Derived Carbon Aerogels: A Sustainable Approach for Advanced Supercapacitor Electrodes
No full textCarbon aerogels (CAs) are porous solids made of a network of interconnected carbon structures that offer
outstanding properties, i.e. low density, electrically conductive frameworks, chemical stability and high
surface to volume ratio. They have been applied in many fields like hydrogen adsorption, catalysis or
energy storage, and many different synthesis techniques have been studied. However, regardless of the
chosen starting material, CAs production involves three fundamental steps: gelation, drying and
carbonization. [1,2]
In particular, the aim of this work is to study structure, morphology, and electrochemical performances of
cellulose based CAs obtained by a facile synthetic route of purification and gelification of Rice Husk (RH).
This new synthetic pathway represents a green and economical alternative that starts from a nontoxic and
biodegradable source of carbon. [3,4]
The process hereby presented involves a two-step pretreatment with NaClO 2 in acetic acid and NaOH in
order to remove lignin, hemicellulose, and silica. After purification the cellulose is dissolved in sodium
hydroxide and urea, aged, regenerated with pure water, freeze dried and carbonized in inert atmosphere at
800°C. CAs were characterized using different techniques to fully understand its structure and best
potential applications. Composition, morphology, and dimensions have been evaluated by scanning
electron microscopy coupled with energy dispersive X-ray spectroscopy, while X-Ray Diffraction and Raman
spectroscopy have been used to investigate structures and graphitization. Finally, the material was applied
as electrodes in symmetric T cells to evaluate its electrochemical performances with cyclic voltammetry and
galvanostatic cyclations.
This study represents a first step to fully understand the potential of rice husk as a green source for
cellulose derived CAs and its most promising applications, and it paves the way to additional investigations
towards the valorization of a low value agricultural waste.
[1] Y. Sheng; Nanoscale, 2020, 12, 19536-19556
[2] L. Jong-Hoon; Carbon, 2020, 163, 1-18
[3] C. Tailong, Journal of Materials Science: Materials in Electronics, 2018, 29, 4334–4344
[4] Z. Zhang; J. Phys. Chem. C, 2019, 123, 38, 23374–2338
Photo-activated carbon dots as catalysts in knoevenagel condensation: An advance in the synthetic field
No full textPhotoinduced chemical reactions and the development of new materials represent a current
and significant topic. We present a sustainable and eco-friendly approach to the Knoevenagel
condensation reaction involving carbonyl and active methylene compounds. Our method utilizes
photo-activated carbon dots (CDs) derived from 5-hydroxymethylfurfural (5HMF) within an aqueous
medium and does not require acidic, basic, or thermal conditions. This protocol operates effectively
with aromatic, aliphatic, and heteroaromatic aldehydes and ketones. The 5HMF-derived-CDs can
be reused four times without significant loss of activity. Moreover, this methodology is suitable for scaling up reactions, thereby highlighting its potential for industrial applications
Response surface methodology for the optimization of phenolic compounds extraction from extra virgin olive oil with functionalized gold nanoparticles
No full textThe optimization of phenolic compounds extraction from extra virgin olive oil (EVOO) was achieved applying a Response Surface Methodology. A simple and straightforward method for the extraction of phenolic compounds from EVOO has been optimized in the presence of functionalized gold nanoparticles (AuNPs). AuNPs were prepared in the presence of Cysteamine as stabilizing thiol (AuNPs-Cys) in order to obtain a water stable colloidal suspension. The obtained AuNPs-Cys, with mean size of about 10 nm were observed by AFM and used as extracting phase of phenolic compounds from EVOO. External parameters influencing the extraction were studied and a Central Composite Design (CCD) was applied for the optimization. The role of AuNPs-Cys quantity (4–12 mg), mixing and contact time (30–120 min), interfering (olive oil quantity) and phenolic compounds concentration (50–500 ppm) were analyzed. An equation model was obtained by applying CCD, with a high significativity (p < 0.0001) and low coefficient of variation value (CV = 3.14%). Optimization of extraction conditions were modulated up to 99%. This model allows to select the optimal extraction conditions to achieve the best performances and can be widely applied
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