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Hybrid mesoporous systems containing a gate-like ensemble functionalised with imidazolium groups and a dye are used for the selective colorimetric sensing of long-chain carboxylates. Amoros del Toro, Pedro Jose, Pedro.Amoros@uv.es

The ease of production, the extreme toxicity of organophosphorus-containing nerve agents, and their facile use in terrorism attacks underscores the need to develop accurate systems to detect these chemicals. Among different technologies we review here recent advances in the design of chromo-fluorogenic methods for the specific detection of nerve agents. Optical sensing (especially colorimetric detection) requires usually low-cost and widely used instrumentation and offers the possibility of so-called “naked eye detection”. Recent reported examples suggest that the application of chromo-fluorogenic supramolecular concepts for the chromogenic or fluorogenic sensing of nerve agents might be an area of increasing interest that would allow developing systems able to overcome some of the limitations shown by classical analytical methods. Costero Nieto, Ana Maria, Ana.Costero@uv.es ; Parra Alvarez, Margarita, Margarita.Parra@uv.es ; Gil Grau, Salvador, Salvador.Gil@uv.es

The combination of nanomaterials as solid supports and supramolecular concepts has led to the development of hybrid materials with improved functionalities. These "hetero-supramolecular" ideas provide a means of bridging the gap between molecular chemistry, materials sciences, and nanotechnology. In recent years, relevant examples have been reported on functional aspects, such as enhanced recognition and sensing by using molecules on preorganized surfaces, the reversible building of nanometer-sized networks and 3D architectures, as well as biomimetic and gated chemistry in hybrid nanomaterials for the development of advanced functional protocols in three-dimensional frameworks. This approach allows the fine-tuning of the properties of nanomaterials and offers new perspectives for the application of supramolecular concepts.

The ionophore 1,4,7,10,13-penta(n-octyl)-1,4,7,10,13-pentaazacyclopentadecane (L1) was used for the development of miniaturised perchlorate-selective electrodes in thick-film technology. Different PVC membranes containing L1 and the plasticizers o-nitrophenyl octyl ether (NPOE), dibutyl phthalate (DBP), bis(2-ethylhexyl)sebacate (DOS) and dibutyl sebacate (DBS) were prepared and placed on a graphite working electrode manufactured by using thick film serigraphic technology. The perchlorate selective electrode containing DBS as plasticizer showed a potentiometric Nernstian response of -57 mV per decade in a range of perchlorate concentration from 1 × 10-4 to 1 × 10-1 M with a detection limit of 5 × 10-5 M. The ion selective electrodes containing DBP and NPOE as plasticizers exhibit a working range from 6.3 × 10-5 to 1 × 10-1 M and 7.4 × 10-5 to 1 × 10-1 M for perchlorate, respectively, with a detection limit of ca. 2.2 × 10-5 M. For all three electrodes a response time of ca. 5 s was found. The prepared electrodes do not show appreciable decay of the slope for at least 25 days. Potentiometric selectivity coefficients (log KpotClO4-,X-) with respect to the primary anion perchlorate were evaluated using the fixed interference method. These coefficients are of the order of 10-1.7 or smaller, indicating the relatively poor interference of the different anions studied.

[EN] Pyrylium-containing mesoporous materials have been used for the chromo-fluorogenic sensing of biogenic amines in an aqueous environment., We thank the Ministerio de Ciencia y Tecnología (MAT2003- 08568-C03-02) for support. F.S. is thankful for a Ramón y Cajal contract. B.G.A. thanks the Generalitat Valenciana and M.C. thanks the Caja de Ahorros del Mediterraneo for a Doctoral Fellowship. A.B.D. thanks the Alexander-von-Humboldt Foundation for a Research Fellowship.

The new ligand 7-methyl-7,13-di-octyl-1,4,10-trioxa-13-aza-7-azonia-cyclopentadecane (L(1)) has been designed, synthesised and used as ionophore in the development ion-selective electrodes for anionic surfactants. Different PVC-membrane anionic-surfactants-selective electrodes were prepared by using L(1) as ionophore and bis(2-ethylhexyl)sebacate (BEHS), dibutyl phthalate (DBP) and nitrophenyl octyl ether (NPOE) as plasticizers. The PVC-membrane electrode containing L(1) and NPOE (electrode E1) showed a Nernstian response to lauryl sulfate with a slope of -59.5mV per decade in a range of concentrations from 1.3x10(-6) to 6.8x10(-3)M and a detection limit of 6.0x10(-7)M. The electrode E1 also showed a reasonable response to other alkyl sulfates and alkylbenzene sulfonates, whereas it does not respond to carboxylates and to cationic and non-ionic surfactants. A similar electrode to E1 but additionally containing the cationic additive n-octylammonium bromide was also prepared (electrode E2) and compared with the response of E1. Selectivity coefficients for different anions with respect to lauryl sulfate were determined by means of the fixed interference method considering lauryl sulfate as the principal anion and using a concentration of 1.0x10(-2)moldm(-3) for the corresponding interfering anion. The selectivity sequence found for the electrode E1 was: LS(-)>SCN(-)>ClO(4)(-)>CH(3)COO(-)>I(-)>HCO(3)(-)>Br(-)>NO(3)(-)>NO(2)(-)>Cl(-)>IO(3)(-)>phosphate>SO(3)(2-)>C(2)O(4)(2-)>SO(4)(2-). Electrode E1 showed remarkably better selectivity coefficients than electrode E2.

[structure: see text] A new sensory MCM-41-based material for the colorimetric sensing and discrimination of amines has been developed.

The development of anion chemosensors is an area of recent interest. We make here a comprehensive review of new advances on anion chemosensing, reported in the literature during the year 2004. The review follows a classification of the sensing systems based on design principles. It comprises: the binding site-signalling subunit approach, the displacement approach and the use of fluoro-chemodosimeters. The first two approximations are based on the use of a suitable anion coordination site coupled with a signalling unit which signals the anion coordination process via changes in its fluorescence behaviour. The two basic subunits are covalently linked in the binding site-signalling subunit approach and not in the displacement approach. In both approaches the fluorescence variation is reversible. The third way to the development of fluorogenic chemosensors is the use of chemodosimeters (also called reagents or reactands) that work usually through irreversible chemical reactions coupled with drastic changes in the fluorescence emission behaviour.

The polyamines, octyl-[2-(2-octylamino-ethylamino)-ethyl]-amine (L(1)) and octyl-{2-[2-(2-octylamino-ethylamino)-ethylamino]-ethyl}-amine (L(2)), have been used as anion ionophores in PVC-based membrane ion-selective electrodes. Different electrodes were prepared containing L(1), or L(2), and o-nitrophenyl octyl ether (NPOE) or bis(2-ethylhexyl)sebacate (DOS) as plasticizers. The response of the electrodes was tested in two different buffers, HEPES-KOH (pH 7) and MES-KOH (pH 5.6). Electrodes containing L(1) and L(2) with NPOE (E1 and E2, respectively) showed a Nernstian response for thiocyanate with a good response time. The detection limit, linear range and slope for electrode E1 were 3.8x10(-6)moldm(-3), 1x10(-5) to 1x10(-1)moldm(-3) and -57.2mVdecade(-1) at pH 5.6 and 4.47x10(-6)moldm(-3), 1.95x10(-5) to 1x10(-1)moldm(-3) and -58.1mVdecade(-1) at pH 7.0. For electrode E2 the detection limit, linear range and slope found were 2.63x10(-6)moldm(-3), 7.94x10(-6) to 1x10(-1)moldm(-3) and -58.5mVdecade(-1) at pH 5.6 and 1.23x10(-5)moldm(-3), 7.95x10(-5) to 1x10(-1)moldm(-3) and -46.0mVdecade(-1) at pH 7. In contrast, electrodes containing DOS as plasticizers gave only response at pH 5.6 (detection limit, linear range and slope at pH 5.6 were 3.16x10(-5)moldm(-3), 1x10(-4) to 1x10(-1)moldm(-3) and -52.6mVdecade(-1)). Selectivity coefficients for different anions with respect to thiocyanate were calculated. The electrode E2 at pH 5.6 was also used for the determination of SCN(-) by potentiometric titrations with Ag(+) ions with good results. The electrode E2 was also used to determine concentrations of thiocyanate in biological samples.

A new chromo-chemodosimeter for the anion sulfide in aqueous environments has been developed. The recognition concept is based on a pyrylium-thiopyrylium transformation that is conveniently drawn toward "color chemistry" concepts by means of the anchoring of an aniline group. This causes the color of the aniline-pyrylium backbone in L1 to change selectively from magenta to blue when transformed to the corresponding aniline-thiopyrylium in the presence of the sulfide anion. The method is simple and easy, suggesting potential applications in a variety of different environments where easy and rapid determination of sulfide might be required.

The 1,3,5-triarylpent-2-en-1,5-dione group selectively undergoes cyclisation and changes its colour from yellow to magenta upon coordination of Hg2+ on a remote site.

The new cyclic polyazacycloalkane 1,4,8,11-tetra(n-octyl)-1,4,8,11-tetraazacyclotetradecane (L1) was synthesised and the copper(II) complex [Cu(L1)]2+ characterised. Different electrodes were prepared using the [Cu(L1)]2+ complex as ionophore, PVC as plastic matrix and o-nitrophenyl octyl ether (NPOE), bis(2-ethylhexyl) sebacate (BEHS) or dibutyl phthalate (DBP) as plasticizers. The electrode containing DBP showed a Nernstian response over a wide pH range and a fast response time (ca. 3 s) whereas NPOE and BEHS gave near-Nernstian slopes. Selectivity coefficients for the different anions with respect to perchlorate were calculated. The response of the electrodes basically followed the Hofmeister sequence, suggesting that interaction of the ionophore with the anions is via electrostatic forces rather than due to anion coordination to the axial sites of the square-planar [Cu(L1)]2+ complex.

The aerial parts of Artemisia spicigera yielded two new eudesmanolides as well as three known ones. The aerial parts of Artemisia verlotiorum yielded four known germacranolides and two known eudesmanolides.

A highly selective colorimetric chemodosimeter for thiol-containing compounds in aqueous solutions is reported. The design protocol makes use of a highly specific reaction between thiols and the electrophilic four-membered ring of highly colored, fluorescent squaraine backbones. At neutral pH selective decoloration and total emission quenching was found due to the rupture of the highly delocalized squaraine framework upon selective nucleophilic addition of thiol-containing derivatives. The squaraine derivatives have been successfully applied to the determination of low-molecular mass aminothiols in human plasma. The method utters the high potential applicability of the chemodosimeter approach in the search for new or improved chromogenic selective or specific probes for target guests.

Design strategies for (bio)chemical systems that are inspired by nature's accomplishments in system design and operation on various levels of complexity are increasingly gaining in importance. Within the broad field of biomimetic chemistry, this article highlights various attempts toward improved and sophisticated sensory materials that rely on the combination of supramolecular (bio)chemical recognition principles and nanoscopic solid structures. Examples range from more established concepts such as hybrid sensing ensembles with improved sensitivity and selectivity or for target analytes for which selectivity is hard to achieve by conventional methods, which were often inspired by protein binding pockets or ion channels in membranes, to very recent approaches relying on target-gated amplified signalling with functionalised mesoporous inorganic supports and the integration of native biological sensory species such as transmembrane proteins in spherically supported bilayer membranes. Besides obvious mimicry of recognition-based processes, selected approaches toward chemical transduction junctions utilizing artificially organized synapses, hybrid ensembles for improved antibody generation and uniquely colour changing systems are discussed. All of these strategies open up exciting new prospects for the development of sensing concepts and sensory devices at the interface of nanotechnology, smart materials and supramolecular (bio)chemistry. © 2011 The Royal Society of Chemistry.

Silica nanoparticles containing polyamines and thiol groups have been used as probes for the selective detection of Tetryl. © 2011 The Royal Society of Chemistry., Financial support from the Spanish Government (project MAT2009-14564-C04-01) and Generalitat Valencia (project PRO-METEO/2009/016) is gratefully acknowledged. Y.S. is grateful to the Spanish Ministry of Science and Innovation for a grant.

Chromogenic cyanide recognition in water was achieved by the use of a hydrophobic dye in micellar containers.

A chromogenic chemosensor for selective pyrophosphate sensing in aqueous environments has been developed using silica functionalised surfaces.

We report herein a new optical sensor for the colorimetric monitoring of aqueous amines designed by anchoring a suitable reactand on a hybrid material that was further incorporated on a polymeric matrix. An azo chromophore containing a trifluoroacetophenone moiety was used as signalling reporter. In this system colour modulation is a consequence of the reversible reaction of the amine with the trifluoroacetyl group that results in the formation of a hemiaminal. Based on this approach but at the same time trying to enhance selectivity the chromoreactand was anchored in a first step onto suitable mesoporous nanoscopic hydrophobic pockets. As a mesoporous system we selected a UVM-7 solid (a MCM41-type material) containing a homogeneous distribution of pores of about 3 nm and a specific surface area of over 1000 m2/g. This material was chemically modified to yield a trifluoroacetylazobenzene indicator dye within the pores, resulting in the hybrid material S3. It was found that whereas the analogous trifluoroacetylazobenzene dye in solution gives an unspecific response, the hybrid material S3 shows enhanced features in terms of selectivity, only reacting with the not-too-large but lipophilic enough aminesn-octylamine and n-decylamine. The material S3 reacts with neither small hydrophilic amines (due to the hydrophobicity of the inner pores in S3) nor very large aliphatic amines (due to the size of the pore). In the second part of this work a composite material (P–S3) was prepared by mixing hydrophilic polyurethane polymer and S3. The X-ray diffraction patterns of P–S3 displays the characteristic intense peak of the MCM-41 type mesoporous material and TEM images show a homogeneous dispersion of the nanometric mesoporous particles into the polymeric matrix. The measurements were carried out in a flow-through module connected to an optical fibre via a Y-probe at pH 9.5 (borax buffer). The P–S3 composite retains the favourable features in terms of selectivity shown by S3 and only displays a clear change in colour for n-octylamine or n-decylamine, but no response to the remaining linear primary amines. The response time of the sensor P–S3 to solutions of these amines was in the range of a few seconds, the regeneration time was between 5 to 10 min and the detection limit was 6 × 10−4 mol L−1. The sensor response was reproducible and reversible.

Silica nanoparticles functionalized with chromogenic spirobenzopyran and thiourea subunits show selective colour changes in the presence of certain long-chain carboxylates.

A remarkable enhanced response towards the hydrophilic anion sulfate using plasticized PVC membranes containing the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and a polyazacycloalkane derivative as ionophore has been found.

A sensory polymeric material for the colorimetric sensing of cyanide in water has been developed based on the reactivity of this anion with the pyrylium cation.

The anthryl-functionalized open-chain polyaza-alkanes L1, L2, and L3 have been synthesized, and their activity as fluorescent chemosensors has been studied in MeCN/H2O 70 : 30 (v/v) and H2O at 25° against the anions bromide, phosphate, sulfate, ATP, ADP, and GMP. The crystal structure of L3 has been solved by single-crystal X-ray-diffraction techniques. The emission intensity of L1 and L2 is selectively quenched in the presence of ATP at acidic pH in MeCN/H2O 70 : 30 (v/v). In H2O, the emission intensity of L1 and L2 is enhanced at neutral pH in the presence of ADP and ATP. The sensing behavior is discussed in terms of H-bonding or electrostatic anion-cation interactions. Receptor L3 does not show any significant change in fluorescence emission upon addition of anions. Protonation constants of the three ligands and stability constants of L2 with phosphate and sulfate were determined by potentiometric titration in MeCN/H2O. The stability constants obtained are compared with those obtained for the interaction of these anions with related open-chain polyamines.

[EN] Chemical communication, based on the exchange of molecules as messengers, allows different entities to share information, cooperate and orchestrate collective behaviors. In recent years, the development of strategies of chemical communication between micro/nanosystems is becoming a key emergent topic in micro/nanotechnology, biomimicry and related areas. In this tutorial review, we provide a general perspective of the concepts used on the topic of chemical communication, and the advances made using different approaches that include nanomaterials, synthetic biology and information-processing tools. Although studies in this direction are very recent, they can be divided in two main categories: (i) communication between abiotic systems and (ii) communication between living and abiotic systems. Using illustrative examples, we give an overview of the ongoing progress, potential applications in different areas and current challenges. The engineering of chemical communication between micro/nanosystems represents a paradigm shift and may open a myriad of new concepts, applications and new technological possibilities in the near future in a number of research fields., We thank the financial support from the Spanish Government (projects RTI2018-100910-B-C41 and RTI2018-101599-B-C22 (MCUI/FEDER, EU)) and the Generalitat Valenciana (project PROMETEO 2018/024) for support. A. L.-L. gratefully acknowledges the COFUND project oLife, which has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 847675. Fig. 4, 7, 8, 17, 18, 23-27, 29 and 30 were created with BioRender.com.