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Metal ion recognition induced by calix[4]arene carbazole containing polymers

Publication . D. Barata, Patrícia; Costa, Alexandra; Fialho, Carina B.; Prata, José Virgílio

Sensing and recognition of ions and neutral molecules via synthetic receptors are of current interest in supramolecular chemistry because of their significant importance in several areas, such as chemistry, biology and environment. Compared with small molecules, polymers-based sensors displayed several importante advantages like signal amplification. In this way, the incorporation of molecular receptors such as calixarenes with conjugated polymer backbones is expected to enhance the signaling events related to a host–guest interaction. The preorganized binding sites, easy derivatization and flexible three-dimensional steric structures make calixarenes ideal construction platforms for molecular design to generate fluorescente receptors. The use of calixarenes as supramolecular scaffolds for this type of architectures has been explored and the sensing abilities of resultant polymers toward metal and molecular ions established. Based on the high sensitivity shown by the non-polymeric analogue CALIX-OCP-CBZ (notshown), to toxic metal cations, we decide two extend the sensing study to polymer materials. Herein, we report the preliminar results of the chemosensing ability of a new bicyclic calix[4]arene-carbazole-polymer (CALIX-OCP-PPE-CBZ) towards the detection of toxic metals in fluid phase.

2018-03Conference object

Open access

Novel bicyclic fluorescent calix[4]arene-based sensors for toxic metals

Publication . Costa, Alexandra; Fialho, Carina B.; Barata, Patrícia; Prata, José Virgílio

Calix[4]arene has been widely exploited as the basic molecular framework for many fluorescent chemosensors in the construction of selective binding sites given its structural rigidity (particularly important when the recognition and reporting events are to be undertaken in fluid phase), various conformations, and facile introduction of fluorophores. Exploring the inherent capabilities of certain fluorescent calixarene scaffolds for establishing strong host:guest interactions, several sensing materials have been recently developed by us [1]. In the same line of research new bicyclic calix[4]arene-based fluorescent chemosensors containing amides as coordination sites (ionophore) and carbazole segments as fluorescent signaling moieties (CALIX-AMD-CBZ) are being developed and that are expected to have high ability toward the detection of metallic cations in solution. However its complex synthesis and characterization has led to the use of a similar compound based on narrow rim 1,3-oxacyclophane tethered calix[4]arene derivatives integrating the same fluorescent segments (CALIX-OCP-2-CBZ) [2] as fluorophore in the present communication. Herein we report the most significant photophysical properties and sensory capabilities of CALIX-OCP-2-CBZ towards divalent ions (Cd2+, Cu2+, Hg2+, Pb2+) by fluorescence spectroscopy in fluid phase.

2017-11Conference object

Open access

How an environmental issue could turn into useful high-valued products: the olive mill wastewater case

Publication . Sousa, D. A.; Costa, Alexandra; Alexandre, M. R.; Prata, José Virgílio

Carbon-based nanomaterials have been directly synthesized fromolivemillwastewaters (OMWWs) for the first time, using expedite and simple environmental-friendly procedures. The OMWWs collected from a mill operating by a two-phase centrifugation system, after being heated (150–300 °C) solely or in the presence of additives for 2–12 h, furnished nanostructuredmaterials in high yields. Under an optimised set of reaction conditions here described, the resultant as-synthetized aqueous dispersions of carbon nanoparticles exhibit outstanding fluorescence emission properties, which encompass an astonishing quantum yield (ΦF N 0.4). The as-prepared carbon nanomaterials show excitation-dependent emissions covering the whole visible spectrum, with a predominant high glow in the blue-green region, and a remarkable photostability. The relevant features attained by the nanomaterials here reported, allied to their easy synthesis and carbon source affordability, render them with unique capabilities to be used in several current and emerging technological applications, namely in bioimaging and nanomedicine, sensorial analysis, (photo)catalysis and optoelectronics. The as-synthesized nanoparticles show a remarkable high sensitivity and selectivity towards haemoglobin.

2019-01-10Journal article

Restricted access

Carbon nanodots from olive mill wastewater: a sustainable route

Publication . Sousa, D. A.; Costa, Alexandra; Alexandre, M. R.; Prata, José Virgílio

Olive oils are obtained from the fruit of the olive tree (Olea europaea L.) by combined mechanical and physical operations. Portugal has a significant production of olive oil (76 k tonnes/year over the last 5 years, 2010-2015) [1]. Olive oil is typically obtained by two main processes: batch press and continuous centrifugation. Depending on the particular process used, 200-1600 L of olive mill wastewater (OMWW) is produced per tonne of processed olives. Taken the lowest of these values, an estimate points to around 15 million L of OMWW may be produced each year in Portugal. The OMWW exhibits very low biodegradability parameters which pose serious issues for its treatment. Sustainable production of high-valued carbon materials from industrial lowvalued and problematic wastes is particularly appealing and highly desirable.

2017-06Conference object

Open access

On the nature of carbon nanodots photoluminescence from olive wastes

Publication . Costa, Alexandra; Prata, José Virgílio

A great structural diversity of carbon nanodots (CNDs) have been obtained in the last ten years by a variety of methods, carbon sources, additives and/or passivating agents, and operation parameters. Not unexpectedly, many properties diverge owing to disparate structural features. The photoluminescence (PL) is one of them. A vast literature is already available on this topic, with findings that are somehow apparently contradictory. At least three possible origins of PL in CNDs have been identified: i) quantum confinement effects associated with the sp2 domains of the carbon core; ii) surface states lying in the edges of sp2 carbogenic core; iii) molecular states originating from molecular species embedded or covalently linked to the carbon matrix.

2017-06Conference object

Open access