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Fruits and vegetables juices present a high supply of polyphenols, making them highly exposed to enzymatic browning. In this work, we report a novel magnetized mesoporous silica material (Fe

A new hierarchical bimodal mesoporous silica, labelled as UVM-12 (acronym of University of Valencia Materials), has been prepared by using a solution of sodium silicate as low-cost silicon source. The final self-assembling between cationic micelles of CTAB and anionic inorganic Si-based oligomers occurs in a homogeneous aqueous medium. The reaction is carried out from low-sized building blocks through a bottom-up approach. The UVM-12 solids combine two mesopore systems according to N2 adsorption–desorption isotherms, what is corroborated by TEM micrographs and XRD patterns. This material has been inorganically modified by incorporation of Al or Ti (M-UVM-12, M = Al, Ti) without alteration of the parent architecture. Moreover, we have carried out a study of the UVM-12 thermal stability by means of N2 adsorption–desorption and XRD. For comparison, in this analysis we have included other two nanoparticulated bimodal silicas that share structure and morphology with UVM-12 (UVM-7 and UVM-10). Both the mesopore wall thickness and the condensation degree (measured through NMR) in the silica framework of each type of material successfully correlates with the thermal stability of their samples.

Wine is one of the most important food products worldwide. However, the application of technologies to the winemaking process can improve. An RGBC optical sensor, used to measure color intensity and shade, was developed and tested in real environments. It is able to measure samples without filtering by offering the color intensity and shade of a filtered sample. Color intensity can be measured within the range of 1.5 and 9.5 color points with an approximate 3% error. The model for shade can be applied to red wines with an approximate 1% error. It can operate directly in cellars under real operating conditions. It avoids collecting samples, and filtering and measuring in a spectrophotometer. It opens the door to automatic and continuous color and shade measurements by increasing knowledge of the process, reducing the cost of analytics and offering enologists a tool to improve wine quality.

[EN] Covalent organic frameworks (COFs) are relatively recent materials. They have received great attention due to their interesting properties. However, the application of microwaves in their synthesis, despite its advantages such as faster and more reproducible processes, is a minority. Herein, a comprehensive compilation of the research results published in the microwave-assisted synthesis (MAS) of COFs is presented. This review includes articles of 2D and 3D COFs prepared using microwaves as source of energy. The articles have been classified depending on the functional groups including boronate ester, imines, enamines, azines, and triazines, among others. It compiles the main parameters of synthesis and characteristics of the materials together with some general issues related with COFs and microwaves. Additionally, current and future perspectives of the topic have been discussed., This research was funded by the Spanish Ministerio de Ciencia, Innovacion y Universidades (RTI2018-100910-B-C44, RTI2018-100910-B-C42 and PEJ2018-004586-A), and the Generalitat Valenciana (CPTTGENT2018/004 and APOTIP/2019/A/023).

Intelligent packaging is an emerging area with a high potentials. Sensors and indicators are key elements, together with enabling technologies, for the development of a new generation of packaging able to interact with the sample and the user. Nanotechnology offers interesting opportunities for the development of active components, integration with the packaging, miniaturization, communication, and batteries. However, its use in intelligent packaging is still limited. We report herein a revision of recent examples of sensors including nanomaterials or nanostructures with potential application in packaging. The references include time temperature indicators, pH, moisture and pressure sensors, but most of the reported examples are based in gas sensors. Systems able to respond to the gases present in the head space are of particular relevance because they can be used for freshness monitoring.

[EN] The effect of silica materials and their functionalization in the lipase catalyzed fat hydrolysis has been scarcely studied. Fifteen silica materials were prepared and their effect on the fat hydrolysis was measured, under simulated duodenal conditions, using the pH-stat method. The materials are composed of the combination of three supports (Stober massive silica nanoparticles, Stober mesoporous nanoparticles and UVM-7) and four surface functionalizations (methyl, trimethyl, propyl and octyl). In addition, the non-functionalized materials were tested. The functional groups were selected to offer a hydrophobic character to the material improving the interaction with the fat globules and the lipase. The materials are able to modulate the lipase activity and their effect depending on the support topology and the organic covering, being able to increase or reduce the fat hydrolysis. Depending of the material, relative fat hydrolysis rates of 75 to 140% in comparison with absence of the material were obtained. The results were analyzed by Partial Least Square Regression and suggest that the alkyl modified mesopores are able to improve the fat hydrolysis, by contrast the non-porous nanoparticles and the textural pores tend to induce inhibition. The effects are more pronounced for materials containing long alkyl chains and/or in absence of taurodeoxycholate., This research was funded by Spanish Ministerio de Ciencia, Innovacion y Universidades, grant number RTI2018-100910-B-C44 and Universitat de Valencia UV-INV_AE18-777438.

Microwaves are a source of energy of great interest for chemical synthesis. Among nanomaterials, few are as versatile as silica—it forms mesoporous materials and nanoparticles, it can be incorporated as shells or loaded in composites, it can also be functionalized. Despite the relevant properties of silica, and the advantages of the use of microwave as energy source, its use in silica-based materials is not frequent. We report herein a compilation of the research results published in the last 10 years of microwave assisted synthesis of silica based materials. This review includes examples of mesoporous materials for waste removal, catalysis, drug release, and gas adsorption applications, together with examples based in the optimization of the synthesis conditions. In the case of non-porous materials, examples of analytical applications, coating of metallic nanoparticles, and SiOx-C materials have been collected.

Polyphenol oxidase (PPO), also known as tyrosinase and catechol oxidase, is the enzyme responsible for enzymatic browning in foods. It causes undesirable organoleptic, nutritional and colour changes. Here, we report the preparation of five nanomaterials and a study of their ability to modulate PPO enzyme activity. The materials consist of UVM-7 supports (a mesoporous silica material) modified with diverse functional groups (i.e. amine, carboxylic acid, isocyanate, alkane and pyridine). We also studied the PPO immobilisation capability of the materials. All the materials, except the carboxylic acid functionalised one, offer high PPO loading capabilities and the immobilisation speed increases with functionalisation. Nevertheless, only a minor effect of the inhibition of enzymatic browning was produced. Furthermore, the amine containing material was able to capture not only PPO, but also the oxidation products. Such behaviour was validated with fresh apple juice in which browning was avoided, even 90 min in the presence of oxygen at room temperature.

Polyphenol oxidase (PPO) enzyme, present in most of fruits and vegetables, frequently induces browning in juices and beverages during postharvest and processing. Many efforts have been done to prevent or avoid this reaction. Nevertheless, the development of new methods is still of interest since many of the current methods present important drawbacks. An overview of the exiting techniques to inhibit enzymatic browning has been compiled in this chapter, including physical (i.e., thermal treatments, high pressures, irradiation, ultrasonication, pulsed electric fields, and ultrafiltration) and chemical techniques (acidification, addition of antibrowning agents) but with particular attention to those based on nanomaterials. The latter includes diverse approaches such as the immobilization of enzymes in nanomaterials, their incorporation as recognition or transducers elements in biosensors, or the use of silver nanoparticles. Finally, recent advances in the use of mesoporous materials to inhibit enzymatic browning in fruit juices have been discussed.

Enzymatic browning in fruits and vegetables can produce undesirable colour changes and adversely affect the taste, flavour, and nutritional value. This fact poses a challenge to the food industry to apply appropriate inhibitors to control enzymatic browning to maintain food quality. Accordingly, this study aims to evaluate the effect of small mazamacrocyclic compounds modified with a hydroxypyridinone similar to kojic acid on enzymatic browning, total polyphenols and antioxidant activity in apple juice. The results showed how these compounds interact with the tyrosinase enzyme in a complex interaction inhibiting its activity. The hydroxypyridinone attached to the macrocycle (I1) was crucial to induce the greatest inhibition, being the most powerful inhibitor. The kinetic studies of I1 reveal mixed-type inhibition over tyrosinase with an IC50 of 0.30 mM, which was much higher than the calculated IC50 for I2 and I3. Furthermore, I1 at a concentration of 2.25 mM, significantly reduced the enzymatic browning in fresh apple juice by more than 50% after 1 h under stirring. Also, it completely stops the decrease in the total phenolic content and delays loss of antioxidant capacity during the first 30 min.

In this work the effect of partial or total replacement of fishmeal by plant protein sources and krill and squid meal on growth performance and shelf-life of gilthead sea bream was evaluated. Plant protein dietswith 50 g kg&minus, 1 of krill and 100 g kg&minus, 1 of squid were supplemented with synthetic amino acidsand at the end of the growing period weight showed no significant differences. The spoilage process of the fish was followed by physicochemical and microbiological measurements together with a colorimetric sensor array (CSA) specially designed for that purpose. The changes in the physicochemical parameters and microbial growth showed that shelf-life of samples were in all cases lower than ninedays. The CSA was not able to show significant differences between both diets, confirming the physicochemical and microbiological results. The fact that the type of feed had no effect on the freshness parameters studied demonstrates that total fishmeal replacement with plant protein blends in the proportions used in this work could be an excellent alternative for feed formulation in aquaculture.

New catalysts based on Pd(0) nanoparticles (Pd NPs) on a bimodal porous silica of the UVM-7/polydopamine (PDA) support have been synthesized following two preparative strategies based on the sequential or joint incorporation of two components of the composite (Pd and PDA). We analyzed the role played by the PDA as &lsquo, interfacial glue&rsquo, between the silica scaffold and the Pd NPs. The catalysts were tested for the hydrogenation of 4-nitrophenol using (NEt4)BH4 as the hydrogenating agent. In addition to the palladium content, the characterization of the catalysts at the micro and nanoscale has highlighted the importance of different parameters, such as the size and dispersion of the Pd NPs, as well as their accessibility to the substrate (greater or lesser depending on their entrapment level in the PDA) on the catalytic efficiency. Staged sequential synthesis has led to better catalytic results. The most active Pd(0) centers seem to be Pd NPs of less than 1 nm on the PDA surface. The efficiency of the catalysts obtained is superior to that of similar materials without PDA. A comprehensive comparison has been made with other catalysts based on Pd NPs in a wide variety of supports. The TOF values achieved are among the best described in the literature.

In this chapter, we report on the diverse applications of silica-based nanomaterials relevant for the food industry. The encapsulation of food ingredients and nutraceuticals and their use as antimicrobial agents and sensors has been explored. In the case of food ingredients, controlled-release materials responsive to pH changes and enzymes (i.e., proteases or esterases) are the main approximation. For antimicrobial agents, the materials are able to modulate the activity of the biocide, increasing the duration of the active substances. Also, an increase of the biocide activity up to ninefold and a broadening of the activity spectra have been observed for a capped material. Finally, due to their present relevance in the sensors area, we review examples of nanogated silica materials and optoelectronic noses.

[EN] The relevance of plant-based food alternatives to dairy products, such as vegetable milks, has been growing in recent decades, and the development of systems capable of classifying and predicting the sensorial profile of such products is interesting. In this context, a methodology to perform the sensorial analysis of vegetable milks (oat, soya, rice, almond and tiger nut), based on 12 parameters, was validated. An electronic tongue based on the combination of eight metals with pulse voltammetry was also tested. The current intensity profiles are characteristic for each non-dairy milk type. Data were processed with qualitative (PCA, dendrogram) and quantitative (PLS) tools. The PCA statistical analysis showed that when using three first principal components, which covered 77% of variance, the eight samples can be differentiated, and the preparation method (artisanal milks or commercial) is one of the main differentiation factors, together with raw material type. The PLS statistical analysis allowed models to be created to predict all 12 sensorial parameters. The goodness of the predictions depends on the parameter being particularly accurate for the body, the granularity in the wall of glass and homogeneity of colour. The results strongly suggest the potential feasibility of using electronic tongues as systems for easy, rapid and effective sensorial assessments of vegetable milks. (C) 2018 Elsevier B.V. All rights reserved., The authors thank the financial support from the Spanish Government (Project MAT2015-64139-C4-1-R) and the Generalitat Valenciana (Project PROMETEOII/2014/047).

We report herein the synthesis and chromo-fluorogenic behaviour of a new probe 1 containing a boron-dipirromethene (BODIPY) unit electronically connected with a dithia-dioxa-aza macrocycle. Acetonitrile and water-acetonitrile 95:5 v/v solutions of the probe showed an ICT band in the visible zone and are nearly non-emissive. When acetonitrile was used as solvent, addition of Hg(II) and trivalent metal cations induced an hypsochromic shift of the absorption band and moderate emission enhancements. A highly selective response was obtained when using competitive media such as wateracetonitrile 95:5 v/v. In this case only Hg(II) induced a hypsochromic shift of the absorption band and a marked emission enhancement., We thank the Spanish Government (MAT2015-64139-C4-1-R) and Generalitat Valenciana (PROMETEOII/2014/047). M. L. P. thanks Generalitat Valenciana for her Grisolia fellowship. Thanks are also due to Fundaça˜o para a Cieˆncia e Tecnologia (Portugal) for financial support to the Portuguese NMR network (PTNMR, Bruker Avance III 400-Univ. Minho), FCT and FEDER (European Fund for Regional Development)-COMPETEQRENEU for financial support to the research centre CQ/UM [PEst-C/ QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302)], and a postdoctoral grant to R. M. F. Batista (SFRH/BPD/79333/2011)., info:eu-repo/semantics/publishedVersion

[EN] Food waste is one of the main issues for international organisms. It is not only an ethical and economic issue but it also depletes the environment of limited natural resources. Among strategies suitable for fighting such challenge, intelligent packaging is an interesting tool to reduce waste derived from households and retailers. A revision of 45 recent advances in the area of optical systems for freshness monitoring is reported herein. The study covers fruits, vegetables, fish products and meat since they are the most representative fields of application. Furthermore, a discussion about the main research challenges and opportunities that will be faced by intelligent packaging in the coming years is included. (C) 2017 Elsevier Ltd. All rights reserved., The authors thank financial support from the Spanish Government (project MAT2015-64139-C4-1-R) and the Generalitat Valenciana (project (Project PROMETEOII/2014/047).

[EN] Darkening processed fruits and vegetables is caused mainly by enzymatic browning through polyphenol oxidase (PPO) action. Accordingly, we explored the potential of four silica-based materials (MCM-41 nanometric size, MCM-41 micrometric size, UVM-7 and aerosil), non-functionalised and functionalised with thiol groups, to inhibit PPO activity in the model system and apple juice. All materials showed relevant performance when immobilising and inhibiting PPO in model systems, and support topology is a main factor for enzyme immobilisation and inhibition. Thiol-containing silica UVM7-SH showed the greatest inactivation, and similar browning values to those obtained by acidification. The enzyme's kinetic parameters in the presence of UVM-7-SH suggested non-competitive inhibition, which indicated that the material interacted with the enzyme, but beyond the active centre. In real systems, UVM-7-SH completely inhibited enzymatic browning in apple juice (cv. Granny Smith and cv. Golden Delicious) up to 9 days after 5 min of contact., The authors thank the financial support obtained from the Spanish Government (Project MAT2015-64139-C4-1-R) and the Generalitat Valenciana (Project GVA/2014/13).

[EN] The aim of this work was to develop and evaluate a rapid, easy-to-use optoelectronic system for the shelf-life assessment of squid in cold storage. For this purpose, an optoelectronic nose was designed, which consisted of an array containing six sensing materials prepared by combining different dyes and two inorganic supports (aluminium oxide and silica gel). Samples were packaged with the colorimetric array and kept in cold storage for 12 days. Squid spoilage was monitored simultaneously by the colorimetric array and by the physico-chemical and microbial analyses during storage. Samples exceeded the acceptability limits for microbial counts on the third day. PCA analysis carried out with CIELab showed that the colorimetric array was able to discriminate between fresh squid fit for consumption and spoiled squid. The statistical models obtained by PLS, with the optoelectronic nose, successfully predicted CO2 and O-2 content in the headspace as well as microbial growth. (c) 2014 Elsevier Ltd. All rights reserved.

A new chromogenic array for the identification and classification of blue cheeses has been developed. It is based on the response of a chromogenic array composed of five sensing materials prepared by the incorporation of pH indicators to MCM-41 and alumina. Four blue cheeses were tested: Roquefort, Blue Stilton, blue cheese with leaves and blue cheese spread. The colour modulations of the chromogenic array were processed by the principal component analysis (PCA) and partial least squares discriminant analysis (PLSDA). The statistical PCA analysis showed different responses to each cheese. PLS-DA models were developed by incorporating the data measured at diverse times, and this approach allowed us to obtain a perfect classification of all five cheeses in 5.5 h. The results suggest that chromogenic arrays and optoelectronic noses can be a suitable approach to develop simple systems to classify blue cheeses and of potential use for the detection of food fraud., We thank the financial support received from the Spanish Government (MAT2012-38429-C04).

[EN] The ability of a number of mesoporous silica materials (SBA-15, SBA-3, and MCM-48) to immobilize polyphenol oxidase (PPO) at different pH has been tested. Pore size and volume are the structural characteristics with higher influence on the PPO immobilization. Mesoropous material SBA-15 adsorbs a larger quantity of PPO at pH 4.00 and offers an inhibition of enzymatic activity close the 50% in apple extracts., AEGB acknowledges support from the Swedish Research Council (Grant Number 621-2012-3375), the ARC Centre of Excellence for Nanoscale BioPhotonics (CE140100003), and an ARC Future Fellowship (FT150100342)

In the past few years, the use of optoelectronic noses based on chromogenic arrays of nonspecific sensors has emerged as a promising, potent, and versatile approach to study complex chemical systems. These arrays are composed by a group of dyes able to offer information through suitable color changes. Optoelectronic noses can be applied to food monitoring and classification offering simple and disposable systems since chromogenic chemosensors are cheap and versatile. Moreover they can be printed on the package and color modulations can be readily measured using simple image capturing systems, such as cameras, and in certain circumstances, they may allow naked eye observation of color changes through transparent films. The combination of dyes with nanomaterials (ie, MCM-41 or UVM-7) and other supports offers synergies derived from the presence of high surface and diverse topologies that influence the array response. As an example of the potential application of optoelectronic noses, we report herein a compilation of the results obtained using arrays of chromogenic indicators with different chemical recognition properties, and how they can be used to follow the evolution of chicken aging, fresh pork sausages spoilage, boiled marinated turkey freshness, and identification of blue cheese varieties.

The design, fabrication and validation of an optoelectronic sensor implemented in an easy-to-use portable device for the selective and sensitive detection of CO in air is reported herein. The system is based on the colour changes observed in the binuclear rhodium complex of formula [Rh2[(C6H4)P(C6H5)2]2(O2CCF3)2](CF3CO2H)2(1) upon coordinating CO molecules in axial positions. Complex 1 is used supported on cellulose chromatography paper. In this support, colour changes to the naked eye are observed for CO concentrations above 50 ppm. The probe is also implemented in a simple portable optoelectronic device.The cellulose support containing probe 1 in this device is placed inside a small dark chamber, is illuminated with a tricolour LED emitting at 624, 525 and 470 nm, respectively corresponding to red (R), green (G) and blue (B) light, and reflected light is detected by a photodiode. With a transimpedance amplifier, the current generated by the photodiode is transformed into a voltage compatible with the 10-bit analogue-to-digital converter (ADC) port. Colour changes are measured as the distance d between the R, G and B data of the blank (probe without CO) and that for a certain CO concentration. Typical calibration curves are fitted using a bi-exponential equation. This system offers a typical response time of a few minutes (ca. 7 min) and a limit of detection of 11 ppm. The probe in the cellulose supports is also highly reversible.The optoelectronic device is portable (dimensions 14 × 8.5 × 3.5 cm; weighs approximately 270 g) and is powered by AA batteries. In addition, no variations in experimental parameter d upon exposure to CO2, N2, O2, Ar, water-saturated air and vapours of chloroform, hexane, ethanol, acetone, methane, toluene or formaldehyde are observed. Besides, colour changes are found for acetonitrile vapour, NO and NO2, but only at high concentrations. For validation purposes, the device was used to determine the CO present in the 4-shed accumulated smoke of two cigarette types after passing smokers lungs., We thank the Spanish Government (Project MAT2012-38429-C04-01), Generalitat Valenciana (Projects PROMETE02009/016 and ISIC/2012/005) and the UPV (Project INNOVA-04-10) for support. M.E.M thanks the Spanish Ministry of Education for a Doctoral FPU Fellowship.

[EN] This review includes examples of silica-based, chromo-fluorogenic nanosensors with the aim of illustrating the evolution of the discipline in recent decades through relevant research developed in our group. Examples have been grouped according to the sensing strategies. A clear evolution from simply functionalized materials to new protocols involving molecular gates and the use of highly selective biomolecules such as antibodies and oligonucleotides is reported. Some final examples related to the evolution of chromogenic arrays and the possible use of nanoparticles to communicate with other nanoparticles or cells are also included. A total of 64 articles have been summarized, highlighting different sensing mechanisms., This research was funded by the Spanish Government (projects RTI2018-100910-B-C41, RTI2018-100910-B-C44, and AGL2015-70235-C2-2-R) and the Generalitat Valenciana (project PROMETEO/2018/024) for support. B.L.-T. is grateful to the Spanish MEC for her FPU grant. Additionally, L.P. thanks the Spanish MEC for his FPI fellowship.

The development of rapid non-destructive techniques to determine fish quality and shelf-life is vital to guarantee food safety. The aim of this study was to evaluate a new optoelectronic nose composed by eight sensing materials prepared by the incorporation of pH indicators and chromogenic reagents selective to metabolites into inorganic materials (aluminium oxide and silica gel) in the shelf-life assessment of fresh sea bream in cold storage. Physico-chemical and microbial analyses were carried out periodically throughout the cold storage, as well as colour measurements on the colorimetric array. The results obtained using the chromogenic array were in accordance with those obtained from physico-chemical and microbial analyses, which showed a clear loss of freshness from day 4 to day 7. This confirms the potential usefulness of colorimetric reagents for detection of sea bream spoilage.

[EN] Trapped: Mesoporous silica nanoparticles were loaded with a fluorescent guest and functionalized with octadecyltrimethoxysilane. The alkyl chains interact with paraffins, which build a hydrophobic layer around the particle (see picture). Upon melting of the paraffin, the guest molecule is released, as demonstrated in cells for the guest doxorubicin. The release temperature can be tuned by choosing an appropriate paraffin. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., Financial support from the Spanish Government (projects MAT2009-14564-C04-01 and SAF2010-15512) and the Generalitat Valenciana (projects PROMETEO/2009/016 and PROMETEO/2010/005) is gratefully acknowledged. L.M. thanks the Generalitat Valenciana for a VALi+d postdoctoral contract. We thank UPV electron microscopy and CIPF confocal microscopy services for technical support.

A novel two-step protocol for the colorimetric detection of ionic surfactants was developed using simple silica supports functionalised with suitable binding groups. Solid S1 was synthesised by reaction of silica with N-methyl-N′-propyltrimethoxysilylimidazolium chloride to obtain a final solid containing imidazolium coordinating moieties. In the first step, solid S1 in contact with anionic surfactant solutions provides the superficial self-assembly organization of the surfactants on the cationic functionalised surface. This layer would be remarkably hydrophobic with the long alkyl chains most likely pointing toward the bulk solution, which in the second step is able to extract a suitable dye (Methylene Blue) from water. The detection principle depends on the fact that the self-assembly process of the anionic surfactant is selective as a consequence of unique strong hydrophobic interactions between surfactant molecules in the monolayer formed. The final behaviour signalling the presence of anionic surfactants would be depletion of the dye solution and coloration of the solid, both visible to the naked eye. A similar protocol was used for the detection of cationic surfactants. In this case solid S2 was prepared containing sulfonate groups. S2 was obtained by reaction of silica with 3-mercaptopropyltriethoxysilane (MPTS) following the oxidation of the mercapto group to sulfonate by adding H2O2. In this case the interaction of cationic surfactants with the S2 surface results in the self-assembly of the cationic surfactants on the anionic surface. In the second step, the addition of a suitable anionic dye (i.e. Patent Blue) then leads to the signalling of the presence of cationic surfactants. S1 and S2 solids were characterised using standard solid-state techniques. A study of the response of these solids was carried out on different concentrations of anionic, cationic and neutral surfactants and in the presence of compulsory water-present anions and cations. The partial decolouration of the dye solution or the corresponding colouration of the solid was related to the concentration of the surfactants in the aqueous solution. The method comprises a novel organic-solvent-free approach for the colorimetric detection of anionic or cationic surfactants. A model was also developed able to interpret the colorimetric behaviour of the solids based on (i) surfactant adsorption on the charged surface and (ii) further extraction of the corresponding dye.

2,4,6-Triphenylthiopyrylium functionalized with an aza-oxa-thia macrocycle is able to selectively recognize Hg2+ cation by a color change and Cu2+ cation by a remarkable significant emission enhancement.

The development of fast and reliable protocols to determine the characteristics of building materials is of importance in order to develop environmentally friendly houses with an efficient energy design. In this article heat flux evolution on different types of clay and concrete bricks has been studied using a guarded hot-plate. The studied bricks were purchased from local commercially available sources and included a solid face brick and a range of honeycombed and perforated bricks. From the data collected a new model to study heat flux is proposed. This model is based on the shape of the typical sigmoidal curves observed for the time dependent heat flux evolution. The model allows the calculation of the thermal resistance (R) and the heat flux in the steady-state (φ∞). The model also calculates two new parameters, tB and τB. tB represents the time at which half φ∞ is attained. This parameter (tB) has additionally been found to be dependent on the thermal diffusivity and the geometric characteristics of the brick.

The synthesis, photophysical properties, protonation, and metal-ion coordination features of a family of nine aniline-based symmetrical squaraine derivatives are reported. The squaraine scaffold displays very attractive photophysical properties for a signalling unit. These dyes show absorption and weakly Stokes-shifted, mirror-image-shaped emission bands in the visible spectral range and there are no hints of multiple emission bands. The mono-exponential fluorescence decay kinetics observed for all the derivatives indicate that only one excited state is involved in the emission. These data stress the interpretation that squaraines can be regarded as polymethine-type dyes. From a coordination chemistry point of view, the squaraines possess four potential binding sites; that is, two nitrogen atoms from the anilino groups and two oxygen atoms from the central C(4)O(2) four-membered ring. These coordination sites are part of a cross-conjugated pi-system and coordination events with protons or certain metal ions affect the electronic properties of the delocalised pi-system dramatically, resulting in a rich modulation of the colour of the squaraines. The absorption band at around 640 nm is blue-shifted when coordination at the anilino nitrogen atoms occurs, whereas coordination to the C(2)O(4) oxygen atoms results in the development of red-shifted bands. Addition of more than one equivalent of protons or metal cations could additionally entail mixed N,O- or N,N-coordinated complexes, manifested in the development of a broad band at 480 nm or complete bleaching in the visible range, respectively. Analysis of the spectrophotometric titration data with HYPERQUAD yielded the macroscopic and microscopic stability constants of the complexes. Theoretical modelling of the various protonated species by molecular mechanics methods and consideration of some of the title dyes within the framework of molecular chemosensing and molecular-scale "logic gates" complement this contribution.

Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption. This hybrid solid is the chemodosimeter for Hg(2+) detection. Hg(2+) reacts with the APC fragment in U1 with release of the squaraine dye into the solution, which turns deep blue and fluoresces strongly. Naked-eye Hg(2+) detection is thus accomplished in an easy-to-use procedure. In contrast, U1 remains silent in the presence of other thiophilic transition metal ions, alkali and alkaline earth metal ions, or anions ubiquitously present in water such as chloride, carbonate, sulfate, and phosphate. Material U1 acts not only as chemodosimeter that signals the presence of Hg(2+) down to parts-per-billion concentrations, but at the same time is also an excellent adsorbent for the removal of mercury cations from aqueous solutions. The amount of adsorbed mercury ranges from 0.7 to 1.7 mmol g(-1), depending on the degree of functionalisation. In addition, hybrid material U1 can be regenerated for both sensing and removal purposes. As far as we know, U1 is the first example of a promising new class of polyfunctional hybrid supports that can be used as both remediation and alarm systems by selective signalling and removal of target species of environmental importance. Model compounds based on silica gel (G1), fumed silica (F1), and micrometre-sized MCM-41 scaffolds (M1) were also prepared and studied for comparative purposes.

A tripodal receptor functionalized with a stilbazolium dye derivative has been designed, synthesized and has been used for the colorimetric discrimination between certain ω-amino acids in mixed DMSO–water 90:10 v/v solutions.

A family of azo dyes containing amide (1), urea (2), thiourea (3), carbamate (4) or amino (5) hydrogen-bond donating groups were synthesized and their response toward anions was studied. Acetonitrile solutions of 1–5 show bright yellow colours, due to charge-transfer bands in the 375–400 nm region, slightly modulated by the electron donor strength of the group attached to the 4′ end of the 4-nitroazobenzene scaffold. Anions of different shape and size (i.e., spherical F–,Cl–, Br– and I–, planar and tetrahedral oxoanions such as NO3–, H2PO4– and HSO4–, carboxylates such as acetate and benzoate and the linear anions cyanide and thiocyanate) were employed in the recognition studies. Two different effects were distinguished: (i) bathochromic shifts of

The heteroleptic osmium(II) complex [Os(L1)(Me-phtpy)][PF6]2 (L1 = 1-[4′-p-tolyl-(2,2′:6′,2″-terpyridyl)]-1,4,8,11-tetraazacyclotetradecane, Me-phtpy = 4′-p-tolyl-2,2′:6′,2″-terpyridine) has been prepared, characterized and its potential use for chemical sensing purposes studied. The complex contains a polyazacycloalkane as “binding site” and a Os(tpy)22+ core that acts as a “signalling subunit”. The emission intensity of the osmium complex was quenched in acetonitrile/water (1:1 v/v) by Cu2+ and Ni2+. Potentiometric titrations of [Os(L1)(Me-phtpy)]2+ in the presence of Cu2+ were carried out in order to determine thermodynamic binding constants in acetonitrile/water (70:30 v/v, 0.1 mol·dm–3 tetrabutylammonium perchlorate). With Cu2+ the receptor [Os(L1)(Me-phtpy)]2+ forms the complex {Cu[Os(L1)(Me-phtpy)]}4+ at neutral pH. Moreover it undergoes two stepwise protonation processes at acid pH related to the partial protonation of the cyclam core and forms two hydroxo complexes at basic pH. The Ni2+ complexes of the osmium receptor [Os(L1)(Me-phtpy)]2+ are able to act as an anion fluorogenic chemosensor in acetonitrile/water mixtures. A displacement of the quenching effect to more acidic pH in the Ni2+–[Os(L1)(Me-phtpy)]2+ system was observed for anions in the order ATP > AMP > chloride. A prospective study of the use of the [Os(L1)(Me-phtpy)]2+ complex as a fluorogenic sensor for oxygen was also carried out by incorporation of the complex in sol-gel silica films made with TEOS and MTEOS. Significant quenching of the osmium fluorescence by oxygen was observed. The oxygen response of the films showed good stability and repeatability. The study suggested that theOs(tpy)22+ core might act as suitable signalling scaffolding in chemical sensing systems of cations, anions and gases.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The behaviour of the naphthoquinone derivatives 4-(4-dimethylamino-phenyl)-[1,2]naphthoquinone (L1) and 4-[4-(1,4,7,10,13-pentaoxa-16-aza-cyclooctadec-16-il)-phenyl]-[1,2]naphthoquinone (L2) as chromogenic chemosensors of metal cations and anions in acetonitrile has been studied. L1 and L2 are highly coloured receptors with a broad band centred at 534 (log e = 3.80) and 532 nm (log e = 3.86), respectively, and attributed to an intra-ligand charge transfer band involving the amine and the carbonyl groups. L1 shows a hypsochromic shift of the absorption band in the visible zone in presence of Cu2+, Fe3+ and Hg2+. Additionally, L2 suffers bleaching induced by the metal cations Pb2+ and Ba2+. In both cases, the data suggested metal cation coordination through the nitrogen atom of the aniline group. 1H NMR studies in the presence of certain metals are also in agreement with this interpretation. log K for the formation of the corresponding [M(L)]2+ complexes have been determined from nonlinear least-squares treatment of the titration profiles. Studies in the presence of anions were also carried out. In acetonitrile a chromogenic sensing of the anions HSO 4 - was observed using the metal complex Ba–L2.

A versatile procedure for anchoring dyes into the pores of multidimensional zeolites by including organic dye precursors in the synthesis gel has been developed. To prove the concept, an aniline-functionalised zeolite Beta was obtained by reaction of triethylorthosilicate (TEOS), tetraethylammonium hydroxide, and N-methyl,N-(propyl-3-trimethoxysilyl)aniline (MPTMSA) in the presence of HF. Further extraction of the structure-directing agents resulted in a highly crystalline, white, functionalised zeolite Beta containing anchored aniline groups. Similar organic functionalised molecular sieves (OFMS) have been explored as novel catalysts, but, as far as we know, OFMS have never been used as precursors for dye-immobilisation or to design new solid-based host systems for selective molecular sensing processes as is reported here. In a second step the solids containing dyes were prepared by reaction of the hybrid material with the appropriate reactives to obtain tricyanovinylbenzene, triphenylpyrylium, azoic, and squaraine derivatives. All these reactions are straightforward and involve electrophilic aromatic substitution or diazotisation reactions at the electron-rich aniline ring. The final dye-functionalised solid materials were isolated by simple filtration and washing procedures and have been characterised by a number of techniques. In all cases the Beta structure of the solid remains unaltered. Among the large number of areas where dye-containing zeolites might be of importance, we were interested in testing their unconventional use as heterosupramolecular hosts in chromogenic protocols. To check their potential use as chemosensors, microporous solids with anchored triphenylpyrilium and squaraine dyes were selected and used as sensors for the chromogenic discrimination of amines. It was found that the response of both solids to amines was basically governed by the three-dimensional (3D) solid architecture that tuned the intrinsic unselective reactivity of the pyrylium dye. By using new solid-state supramolecular chemistry protocols we believe that these, and similar future dye-zeolite hosts, might be promising new sensor materials allowing the visible discrimination of selected target guests by size and/or polarity within families or closely related molecules.

The synthesis and characterisation of a family of multi-channel receptors containing crown-cation binding sites anchored to a 1-aminophenyl-1,2,2-tricyanoethylene group is reported. The ligands L1–L6 bear a 1-aminophenyl-1,2,2-tricyanoethylene scaffolding which is simultaneously a redox-active group (showing reduction processes at moderately modest potentials) and an acceptor moiety in the 1-aminophenyl-1,2,2-tricyanoethylene chromophore. Additionally, dyes L1–L6 also show fluorescence emission. The colour variation of L1–L6 in acetonitrile in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Pb2+ and Zn2+ has been studied. Selective hypsochromic shifts were found for the systems L4-Pb2+, L5-Hg2+ and L6-Hg2+. For Hg2+ with L5 and L6 and Pb2+ with L4, emission fluorescence enhancements most likely associated with metal coordination to the anilinium nitrogen were observed. The electrochemical behaviour of receptors L1–L6 was studied in acetonitrile with platinum as working electrode and [Bu4N][BF4] as supporting electrolyte. This family of receptors shows a one-electron reversible reduction process at around –0.70 V vs. SCE, attributed to the reduction of the tricyanovinyl group. Additionally, all the receptors also show the oxidation of the anilinium moiety at about 1.2–1.4 V vs. SCE. Significant anodic shifts of both reduction and oxidation waves were found in the presence of certain metal cations. The relationship of these multiple-channel signalling receptors with guest chemosensing and reconfigurable molecular-based logic gates is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

[EN] Chemical burns, mainly produced by acids, are a topic of concern. A new sensing material for the detection of strong acids able to be incorporated into textiles has been developed. The material is prepared by the covalent attachment of 2,2 ',4,4 ',4 ''-pentamethoxy triphenyl methanol to a mesoporous material which further is included in a nitro resin to obtain a colourless composite. The response of this composite to diverse acid solutions was tested showing the appearance of an intense purple colour (with a colour difference higher than 160) that can be monitored by the naked eye or could be easily digitised to feed an instrumental sensor. Reversibility and resistance to washing cycles were studied with positive results. Finally, the response of the sensing composite to acid vapours was assayed, observing a colour change similar to that found in solution., The authors thank the financial support from the Spanish Government (project MAT2015-64139-C4-1-R) and the Generalitat Valenciana (project PROMETEOII/2014/047).

A chromogenic array for monitoring boiled marinated turkey meat freshness in a modified packaging atmosphere (30% CO2, 70% N2) has been developed. The chromogenic array was combined with commodity tools such as digital camera and Photoshop to extract and analyse the colour changes. The array was composed of 16 sensing materials prepared through the combination of 13 indicators (including pH indicators, nucleophilic sensing dyes, etc.) and three different inorganic supports (i.e., UVM-7, alumina and silica gel). The chromogenic data obtained from the array showed characteristic fingerprints for each sampling day (0, 3, 10, 17, 24, 31, 38 and 45 days post-package). Statistical analysis by HCA of the chromogenic data allowed classifying the samples as fresh , not fresh and not edible . Besides, microbiological and sensorial determinations on the packaged samples were also carried out. From these studies a shelf life of 38 days at 4 °C was determined. Colour differences from the chromogenic array were employed to create PLS models for aerobic mesophilic bacteria count, sensory score and storage time with quite good results., We thank the financial support from the Spanish Government (projects CIT-060000-2008-14 and MAT2012-38429-C04), the Generalitat Valenciana (PROMETEO/2009/016) and UPV (PAID 2414). Y.S. also thanks the Spanish Ministry of Science for a PhD fellowship.

We report herein the development of a new optoelectronic nose composed of seven sensing materials prepared by the incorporation of pH indicators and chromogenic reagents selective to metabolites into inorganic materials (UVM-7 and alumina). The nose has been applied to monitor fresh pork sausage ageing. Sausages were packaged together with the disposable array in a modified packaging atmosphere (30% CO2, 70% N2) and colour changes were measured at seven day intervals. Simultaneously, microbiological and sensory analyses were performed. Colour modulations of the chromogenic array were processed with standard analytical tools, including principal component analysis (PCA) and partial least squares (PLS). According to the PCA, the array was able to monitor the sausage spoilage process and to distinguish between each sampled day. Moreover, the PLS statistical analysis of the chromogenic data displayed a linear correlation between the predicted and measured values of the storage days, mesophilic bacteria (cfu g−1) and the sensory score with regression coefficients of 0.9300, 0.9472 and 0.9381, respectively., The financial support from the Spanish Government (projects CIT-060000-2008-14 and MAT2009-14564-004-01), the Generalitat Valenciana (PROMETEO/2009/016) and UPV (PAID 2414) is gratefully acknowledged. Y.S. also thanks the Spanish Ministry of Science for a PhD fellowship.

[EN] An optoelectronic nose for monitoring Atlantic salmon (Salmo salar) spoilage has been developed. The chromogenic array uses eight sensing materials containing pH and a Lewis acid indicator adsorbed in aluminium oxide or silica gel. Colour modulations as RGB coordinates are measured on day 0 and for the salmon samples held in cold storage for 2, 5, 7 and 9 days. For the same days volatile basic nitrogen (TVB-N) and (mesophilic, psychrotrophic and H2S-producing bacteria) analyses were carried out. Changes in the RGB coordinates in the chromogenic array are processed with qualitative (PCA) and quantitative (PLS) tools. The chromogenic data obtained from the array is correlated with the physico-chemical and microbiological parameters (TVB-N, H2S producing, mesophilic and psychrotrophic bacteria) via PLS statistical studies. The influence of the use of two cross-validation methods (Venetian and Random) and diverse number of data splits (NDS) (2 4) to determine the number of PLS components is discussed. The suitability of the PLS models is also studied via t u score plots. The results suggest the potential feasibility of this system for S. salar freshness monitoring Highlights • A chromogenic array for monitoring salmon (Salmo salar) spoilage has been developed. • PLS displayed a good prediction for TVB-N and psychrotrophic bacteria counts. • The relationship in the data for TVB-N and psychrotrophic legitimate the PLS models. • PCA was able to distinguish between different sampled days., The financial support from the Spanish Government (project MAT2012-38429-C04-01), the Generalitat Valenciana (project PROMETEO/2009/016) and Universitat Politecnica de Valencia (project Ref. 2711) is gratefully acknowledged.

[graph: see text] In this paper, the use of aggregation processes in squaraine derivatives as signaling protocols in the development of colorimetric probes for certain neutral guest (aromatic hydrocarbons) has been studied.

[EN] A new optoelectronic nose for the shelf-life assessment of fresh sea bream in cold storage has been developed. The chromogenic array used eight sensing materials (based on aluminium oxide and silica gel) containing pH indicators, Lewis acids and an oxidation reduction indicator. The colour changes of the sensor array were characteristic of sea bream spoilage. Colour modulations were measured on day 0 and for the samples held in cold storage for 2, 4, 7, 9 and 11 days. Determination of moisture content, pH, total volatile basic nitrogen (TVB-N), drip loss, ATP-related compounds and K1-value and microbial (mesophilic bacteria and Enterobacteriaceae) analyses were carried out on the same days. The changes in the chromogenic arrays data were processed by statistical analysis (PCA). Moreover, PLS statistical studies allowed the creation of models to correlate the chromogenic data with concentrations of mesophilic and Enterobacteriaceae. The results suggest the feasibility of this system to help develop optoelectronic noses for fish freshness monitoring., The financial support from the Spanish Government (Project MAT2009-14564-004), the Generalitat Valenciana (Project PROMETEO/2009/016) and Universitat Politecnica de Valencia (Project Ref. 2711) is gratefully acknowledged.