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A simple, efficient, and reversible fluorescent sensor probe, PBA (2,6-dimethyl pyrone barbituric acid conjugate), comprised of a pro-aromatic donor conjugated with a barbituric acid, was developed for the detection of highly toxic mercuric ions. The probe showed high selectivity and "Turn-On" fluorescence response towards Hg2+ among various metal cations such as Na+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, and Pb2+, in both homogeneous and microheterogeneous micelle medium sodium dodecyl sulphate (SDS). The binding stoichiometry, limit of detection (LOD), and binding constant for the PBA-Hg complex were determined. The mechanism of binding was ascertained using the N,N'-dimethylbarbituric acid conjugate of 2,6-dimethylpyran (PDMBA), where no binding interaction by deprotonation is possible. In the presence of cysteamine hydrochloride and trifluoroacetic acid (TFA), the complexation of Hg2+ with PBA was demonstrated to be reversible, indicating its potential for the development of reusable sensors. Moreover, the practical applicability of PBA in monitoring Hg2+ in living cells was also evaluated. [ABSTRACT FROM AUTHOR]

Antibiotic residues are currently an increasing threat for human health and the ecosystem, and specific and rapid real‐time sensing of antibiotics is a big challenge. To realize specific sensing by rapid fluorescent sensors, a lanthanide metal‐organic framework (MOF) containing dual emissive centers has been developed with high sensing selectivity and sensitivity. Owing to the self‐calibration ability, the dual‐center Tb‐MOF exhibits higher selectivity towards furazolidone (FZD) and nitrofural (NZF) among the reported MOF sensors. Additionally, the corresponding ratiometric detection mode also realized specific sensing of other tested antibiotics. Besides, the single‐Tb3+‐based dual‐emission MOF in this work is expected to support the development of fluorescent sensors with high sensitivity and selectivity for environmental safety purposes. [ABSTRACT FROM AUTHOR]

Here we address an important roadblock that prevents the use of bright fluorescent nanoparticles as individual ratiometric sensors: the possible variation of fluorescence spectra between individual nanoparticles. Ratiometric measurements using florescent dyes have shown their utility in measuring the spatial distribution of temperature, acidity, and concentration of various ions. However, the dyes have a serious limitation in their use as sensors; namely, their fluorescent spectra can change due to interactions with the surrounding dye. Encapsulation of the d, e in a porous material can solve this issue. Recently, we demonstrated the use of ultrabright nanoporous silica nanoparticles (UNSNP) to measure temperature and acidity. The particles have at least two kinds of encapsulated dyes. Ultrahigh brightness of the particles allows measuring of the signal of interest at the single particle level. However, it raises the problem of spectral variation between particles, which is impossible to control at the nanoscale. Here, we study spectral variations between the UNSNP which have two different encapsulated dyes: rhodamine R6G and RB. The dyes can be used to measure temperature. We synthesized these particles using three different ratios of the dyes. We measured the spectra of individual nanoparticles and compared them with simulations. We observed a rather small variation of fluorescence spectra between individual UNSNP, and the spectra were in very good agreement with the results of our simulations. Thus, one can conclude that individual UNSNP can be used as effective ratiometric sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • One-pot synthesis of chitosan embedded with P and N co-doped carbonized polymer dots was achieved in 60 sec. • In situ formed P, N-CPDs exhibited upconverted emission after excitation at 710 nm. • A novel ratiometric upconversion scatter sensor was developed for determination of α-lipoic acid. • α-lipoic acid could selectively be detected in the presence of highly absorbing coexisting compounds. The rapid sensitive determination of α-lipoic acid (ALA) is essential for monitoring biological functions. Nevertheless, the lack of chromophore and its occurrence in complex biological matrices renders its determination challenging and requires additional treatment steps which lengthen assay procedure and affects method sensitivity. Herein, through the coordination of frequency doubling scatter (FDS) of polysaccharide strands with up-conversion of the embedded in situ formed P, N- carbonized polymer dots (CPDs), a novel ratiometric sensing platform was constructed. One-pot synthesis of chitosan decorated P, N-CPDs (chitosan@ P,N-CPDs) was attempted through microwave-assisted crosslinking-accelerated carbonization, using phosphoric acid as crosslinker and dopant. The constructed platform responded to the presence of α-lipoic acid (ALA) in concentration dependent manner (R2 = 0.995) between 1.65–100 μg/mL, with detection limit of 0.55 μg/mL, good accuracy (%E = 0.52 %) and precision (%RSD < 2 %). Consistent results with comparison method confirmed sensor reliability for determination of ALA in urine, Thiotacid® and Thiotacid compound® tablets, with no interference from the coexisting highly absorbing water-soluble vitamins, thiamine, and cyanocobalamin, or other potential interferents. Thus, the developed high performance sensing platform could be adopted for ALA determination as it is much less prone to spectral interferences and hence more discerning than those operated in single wavelength mode. [ABSTRACT FROM AUTHOR]

Cholesterol is an essential component of the mammalian plasma membrane involved in diverse cellular processes. Our recent quantitative imaging analysis using ratiometric cholesterol sensors showed that the available cholesterol concentration in the inner leaflet of the plasma membrane (IPM) is low in unstimulated cells and increased in a stimulus-specific manner to trigger cell signaling events. However, the transbilayer distribution of cholesterol in the plasma membrane of mammalian cells remains controversial. Here we report a systematic and rigorous evaluation of basal IPM cholesterol levels in a wide range of mammalian cells with different properties employing cholesterol sensors derived from the D4 domain of the Perfringolysin O toxin and a sterol-transfer protein, Osh4. Results consistently showed that, although basal IPM cholesterol levels vary significantly among cells, they remain significantly lower than cholesterol levels in the outer leaflets. We found that IPM cholesterol levels were particularly low in all tested primary cells. These results support the universality of the low basal IPM cholesterol concentration under physiological conditions. We also report here the presence of sequestered IPM cholesterol pools, which may become available to cytosolic proteins under certain physiological conditions. We hypothesize that these pools may partly account for the low basal level of available IPM cholesterol. In conclusion, we provide new experimental data that confirm the asymmetric transbilayer distribution of the plasma membrane cholesterol, which may contribute to regulation of various cellular signaling processes at the plasma membrane.

[Display omitted] • Ratiometric sensors (Eu-MPA-InP/ZnS) for multi-colour detection of tetracycline. • It showed strong adaptability and resistance in several real food samples. • Portable 96-well agarose gel device facilitates real-time on-site tetracycline detection via smartphone. • The method offers new prospects for InP QDs fluorescent sensors in the analysis of environmental pollutants. A turn-on type ratiometric fluorescence sensing system of blue quantum dot Eu-MPA-InP/ZnS was established for multi-color visualization determination of tetracycline (TC). Mercaptopropionic acid (MPA)-capped InP/ZnS quantum dots (MPA-InP/ZnS QDs) both modify the hydrophilicity of InP/ZnS QDs and serve as a scaffold for coordinating of Eu3+ ions. The blue fluorescence of Eu-MPA-InP/ZnS at 478 nm is reduced by the TC through the inner filter effect (IFE) under a single excitation wavelength of 365 nm. Rich colour gradients and a highly discriminative colour change were features of this multicolour response to TC, which allowed visual quantification of TC in a dose-dependent manner. Furthermore, by cross-linking Eu-MPA-InP/ZnS with agarose (Aga.), a mouldable Eu-MPA-InP/ZnS@Aga 96-well gel sensing device was designed to serve as a handheld sensor for on-site detection of TC. This probe expands the use of InP QDs in analytical sensing and has been effectively applied to the visual detection of tetracycline in milk and the environment. [ABSTRACT FROM AUTHOR]

Self-powered electrochemical sensors based on photofuel cells have attracted considerable research interest because their unique advantage of not requiring an external electric source, but their application in portable and multiplexed targets assay is limited by the inherent mechanism. In this work, a portable self-powered sensor constructed with multichannel photofuel cells was developed for the ratiometric detection of mycotoxins, namely ochratoxin A (OTA) and patulin (PAT). The spatially resolved CdS/Bi 2 S 3 -modified photoanodes and a shared Prussian Blue cathode were integrated on an etched indium-tin oxide slide to fabricate the multichannel photofuel cell. The aptamers of OTA and PAT were covalently bonded to individual photoanode regions to build sensitive interfaces, and the specific recognition of analytes impaired the output performance of constructed PFC. Accordingly, ratiometric sensing of OTA and PAT was achieved by utilizing the output performance of a control PFC as a reference signal. This approach effectively eliminates the impact of light intensity on the accuracy of the detection. Under the optimal conditions, the proposed sensing chip exhibited linear ranges of 2.0–1000 nM and 5.0–500 nM for OTA and PAT, respectively. The detection limits (3 S/N) were determined to be 0.25 nM for OTA and 0.27 nM for PAT. The developed ratiometric sensing method demonstrated good selectivity and stability in the simultaneous detection of OTA and PAT. It was successfully utilized for the analysis of OTA and PAT real samples. This work provides a new perspective for construction of portable and ratiometric self-powered sensing platform. [Display omitted] • A portable self-powered aptasensing platform based on photofuel cell (PFC) was proposed. • Spatially resolved CdS/Bi 2 S 3 photoanodes-based multichannel PFC was fabricated. • Ratiometric sensing of ochratoxin A (OTA) and patulin (PAT) were realized using the sensing platform. • The developed method exhibited satisfactory recovery for detection of OTA and PAT in real sample. [ABSTRACT FROM AUTHOR]

Precisely determining the intracellular concentrations of metabolites and signaling molecules is critical in studying cell biology. Fluorogenic RNA‐based sensors have emerged to detect various targets in living cells. However, it is still challenging to apply these genetically encoded sensors to quantify the cellular concentrations and distributions of targets. Herein, using a pair of orthogonal fluorogenic RNA aptamers, DNB and Broccoli, we engineered a modular sensor system to apply the DNB‐to‐Broccoli fluorescence ratio to quantify the cell‐to‐cell variations of target concentrations. These ratiometric sensors can be broadly applied for live‐cell imaging and quantification of metabolites, signaling molecules, and other synthetic compounds. [ABSTRACT FROM AUTHOR]

Fluorescent carbon dots (CDs) are a new class of carbon nanomaterials and have demonstrated excellent optical properties, good biocompatibility, great aqueous solubility, low cost, and simple synthesis. Since their discovery, various synthesis methods using different precursors were developed, which were mainly classified as top-down and bottom-up approaches. CDs have presented many applications, and this review article mainly focuses on the development of CD-based fluorescent sensors. The sensing mechanisms, sensor design, and sensing properties to various targets are summarized. Broad ranges of detection, including temperature, pH, DNA, antibiotics, cations, cancer cells, and antibiotics, have been discussed. In addition, the challenges and future directions for CDs as sensing materials are also presented. [ABSTRACT FROM AUTHOR]

Mono-dispersed polystyrene-based microspheres with diameters about 1 μm encapsulating rhodamine moieties as oxygen insensitive internal reference probes and platinum octaethylporphyrin units as oxygen sensitive probes were synthesized as new ratiometric oxygen sensors (Rhod-PtOEP-PS). The dual luminophors of rhodamines and platinum porphyrin moieties exhibited emissions maxima at 585 nm and 644 nm, respectively. The microspheres showed good oxygen sensing properties in different oxygen partial pressures (pO 2 ) and dissolved oxygen (DO) concentrations. It was found the oxygen probes and reference probes in microspheres showed higher photo-stability than their corresponding free fluorophores in solution. The microspheres also showed good sensitivity for air-pressure and cellular oxygen in cell culture medium. These microspheres were used to detect DOs in a few kinds of liquids including some daily drinks and it was found the measured errors were within positive/negative 11% as compared with the measured results using traditional oxygen electrodes. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals (PNCs) have emerged as advanced materials for various applications. Herein, we developed oxygen insensitive PNCs in polymer matrices and applied them as internal reference to achieve ratiometric sensing for oxygen. Significant emission color changes from orange under nitrogen to green under oxygen were observed. Further micro-patterned sensors were prepared by micro/nano-imprint technology. Results showed that all these micro-structures increased sensors’ sensitivity, however, affected sensors response time significantly. The film with pinholes slowed down the response times; the films with pillars shorted the response time. Therefore, for the first time we prepared new PNCs-based ratiometric gaseous oxygen sensing films and further prepared micro-structured sensors. This study may broaden the applications of perovskite materials and also oxygen sensors. [ABSTRACT FROM AUTHOR]

Abstract: This work presents two molecular fluorescent probes 1 and 2 for the selective determination of physiologically relevant K+ levels in water based on a highly K+/Na+ selective building block, the o‐(2‐methoxyethoxy)phenylaza‐18‐crown‐6 lariat ether unit. Fluorescent probe 1 showed a high K+‐induced fluorescence enhancement (FE) by a factor of 7.7 of the anthracenic emission and a dissociation constant (Kd) value of 38 m m in water. Further, for 2+K+, we observed a dual emission behavior at 405 and 505 nm. K+ increases the fluorescence intensity of 2 at 405 nm by a factor of approximately 4.6 and K+ decreases the fluorescence intensity at 505 nm by a factor of about 4.8. Fluorescent probe 2+K+ exhibited a Kd value of approximately 8 m m in Na+‐free solutions and in combined K+/Na+ solution a similar Kd value of about 9 m m was found, reflecting the high K+/Na+ selectivity of 2 in water. Therefore, 2 is a promising fluorescent tool to measure ratiometrically and selectively physiologically relevant K+ levels. [ABSTRACT FROM AUTHOR]

Abstract: In this work we investigate a mesoporous silica (MS) decorated with dipyridyl‐pyridazine (dppz) ligands and further grafted with a mixture of Eu3+/Tb3+ ions (28.45%:71.55%), which was investigated as a potential thermometer in the 10–360 K temperature range. The MS material was prepared employing a hetero Diels–Alder reaction: 3,6‐di(2‐pyridyl)‐1,2,4,5‐tetrazine was reacted with the double bonds of vinyl‐silica (vSilica) followed by an oxidation procedure. We explore using the dppz‐vSilica material to obtain visible emitting luminescent materials and for obtaining a luminescent thermometer when grafted with Eu3+/Tb3+ ions. For the dppz‐vSilica@Eu,Tb material absolute sensitivity Sa of 0.011 K−1 (210 K) and relative sensitivity Sr of 1.32 %K−1 (260 K) were calculated showing good sensing capability of the material. Upon temperature change from 10 K to 360 K the emission color of the material changed gradually from yellow to red. [ABSTRACT FROM AUTHOR]

Measuring temperature with greater precision at localized small length scales or in a nonperturbative manner is a necessity in widespread applications, such as integrated photonic devices, micro/nano electronics, biology, and medical diagnostics. To this context, use of nanoscale fluorescent temperature probes is regarded as the most promising method for temperature sensing because they are noninvasive, accurate, and enable remote micro/nanoscale imaging. Here, we propose a novel ratiometric fluorescent sensor for nanothermometry using carbon nanodots (C-dots). The C-dots were synthesized by one-step method using femtosecond laser ablation and exhibit unique multi-emission property due to emissions from abundant functional groups on its surface. The as-prepared C-dots demonstrate excellent ratiometric temperature sensing under single wavelength excitation that achieves high temperature sensitivity with a 1.48% change per °C ratiometric response over wide-ranging temperature (5–85 °C) in aqueous buffer. The ratiometric sensor shows excellent reversibility and stability, holding great promise for the accurate measurement of temperature in many practical applications. [ABSTRACT FROM AUTHOR]

A current conveyor-based analog electronic interface for differential capacitive sensors is here shown. The read-out circuit that utilizes second generation Current Conveyors (CCIIs) as active blocks is able to evaluate differential capacitive variations performing a capacitance-to-voltage conversion. This solution has been implemented both in a discrete element board and as integrated version in a standard 350 nm CMOS technology. Simulations and experimental results have shown a linear input/output characteristic and a good agreement with theoretical expectations, being the former performed for both the designed solutions, whereas the latter only for a discrete prototype board (employing a low cost commercial component (AD844). Sensitivity and resolution data on a practical case-study of a displacement sensor are constant and their values are satisfactory. Both simulated and measured results make the proposed architecture a good candidate as first stage of analog front-ends to be employed in differential capacitive instrumentation. [ABSTRACT FROM AUTHOR]

A novel fluorescent BODIPY-rhodamine dyad probe that operates based on through bond energy transfer (TBET) phenomenon has been synthesized and its application in the detection of biologically relevant metal ions is explored. Among several metal ions, the probe selectively responds to the addition of trivalent metal ions (Al 3+ , Cr 3+ and Fe 3+ ) through its signature absorbance and fluorescence characteristics and permits their ratiometric detection. The trivalent metal ion detection ability of the probe is unaffected with the presence of other commonly coexistent ions. The probe is highly sensitive and it can detect the trivalent metal ions even at ppb level concentrations. The probe is nontoxic under the experimental conditions, cell permeable and useful for the imaging of Al 3+ , Cr 3+ and Fe 3+ ions present in W138 (normal lung fibroblast) cells. [ABSTRACT FROM AUTHOR]

In this study, preparation of novel pH-sensitive N-doped carbon dots (NCDs) using glucose and urea is reported. The prepared NCDs present strong excitation-dependent fluorescence changes towards the pH that is a new behavior from these nanomaterials. By taking advantage of this unique behavior, two separated ratiometric pH sensors using emission spectra of the NCDs for both acidic (pH 2.0 to 8.0) and basic (pH 7.0 to 14.0) ranges of pH are constructed. Additionally, by considering the entire Excitation–Emission Matrix (EEM) of NCDs as analytical signal and using a suitable multivariate calibration method, a broad range of pH from 2.0 to 14.0 was well calibrated. The multivariate calibration method was independent from the concentration of NCDs and resulted in a very low average prediction error of 0.067 pH units. No changes in the predicted pH under UV irradiation (for 3 h) and at high ionic strength (up to 2 M NaCl) indicated the high stability of this pH nanosensor. The practicality of this pH nanosensor for pH determination in real water samples was validated with good accuracy and repeatability. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanodots (CNDs) with conspicuous dual emission (at 450 and 517 nm) were fabricated by hydrothermal treatment of aqueous sucrose solution. The temperature‐dependent photoluminescence (PL) and time‐resolved PL were investigated. The trapping of excited electrons by the nonradiative defects should substantially account for the PL quenching as the temperature increases. The sucrose‐derived CNDs show great potential for applications as ratiometric fluorescent thermometers with a sensitivity of approximately 2.15 % °C−1. [ABSTRACT FROM AUTHOR]

A rhodamine–naphthalimide dyad probe, 1 , that selectively responds to the addition of trivalent metal ions (Fe 3+ or Al 3+ or Cr 3+ ) via ultrafast Förster resonance energy transfer (FRET) from naphthalimide to rhodamine is designed and synthesized. 1 is highly selective to the trivalent metal ions and the presence of other monovalent or divalent metal ions do not affect its detection ability. The probe is highly sensitive and it can respond to the presence of trivalent metal ions even at sub-micromolar levels. 1 is stable over a broad range of pH, non-toxic under experimental conditions and suitable to the fluorescence bio-imaging of live cells exposed to trivalent metal ions. The trivalent metal ion induced ultrafast energy transfer kinetics of 1 is explored using time resolved fluorescence experiments. [ABSTRACT FROM AUTHOR]

A novel fluorescein-rhodamine dyad probe has been synthesized and its chemosensory applications are explored. Anion and cation specific responses of the probe permit ratiometric detection of Hg 2+ and fluoride ions, individually and collectively, with different fluorescence outputs. The presence of other commonly coexistent ions does not affect the Hg 2+ and fluoride ion detection ability of the probe. The probe is highly sensitive to Hg 2+ and fluoride ions and it can detect Hg 2+ and fluoride ions even at ppb level concentrations. The probe is non-toxic under the experimental conditions, cell permeable and useful for the imaging of intracellular Hg 2+ and fluoride ions. [ABSTRACT FROM AUTHOR]

Abstract: Spectral analysis by chemometric methods is applied to optical pH sensing with aminofluorescein as fluorescent indicator. This method is superior to the ratiometric dual-wavelength detection when the pH value influences the spectrum in a complex way. In the case of aminofluorescein the range of measurement is extended compared to the ratiometric method. The pH value can be calculated from the fluorescence spectra of the indicator independently of the absolute intensity and of the temperature of the sample. At high indicator concentrations the fluorescence spectra are strongly influenced by inner filter effects and the error of the pH prediction is significantly smaller than in a dilute solution. The reduction of the fluorescence spectra to a few data points shows that the chemometric pH determination does not require high-resolution spectral sensors. [Copyright &y& Elsevier]

Changes in intracellular GTP levels, even incremental ones, profoundly affect the activity of several GTP-binding proteins ultimately resulting in alteration of several basal cellular phenotypes including cell motility, invasion, and tumorigenesis. However, until recently, no tools were available for GTP quantification in live cells. Therefore, in the current chapter, we describe the methodology for the quantitative assessment of spatiotemporal changes in GTP levels in the cells using genetically encoded fluorescent ratiometric GTP sensors termed GEVALs for GTP evaluators., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Imaging the cellular dynamics of metabolites and signaling molecules is critical for understanding various metabolism and signal transduction pathways. Genetically encoded RNA-based sensors are emerging powerful tools for this purpose. However, it was challenging to use these sensors to precisely determine the intracellular concentrations of target analytes. To solve this problem, we have recently developed ratiometric sensors using an orthogonal pair of RNA/fluorophore conjugates: Broccoli/DFHBI-1T (3,5-difluoro-4-hydroxybenzylidene-1-trifluoroethyl-imidazolinone) and DNB (dinitroaniline-binding aptamer)/SR-DN (sulforhodamine B-dinitroaniline). The cellular DNB-to-Broccoli fluorescence intensity ratio can be directly applied to quantify the target concentrations at the single-cell level. Unfortunately, due to the instability of the SR-DN dye, this ratiometric sensor is difficult to use for monitoring target dynamics. Herein, by replacing SR-DN with a stable TMR (tetramethylrhodamine)-DN dye, we developed a ratiometric sensor system based on Broccoli/DFHBI-1T and DNB/TMR-DN, which can be used for dynamic imaging in living cells. We believe these advanced genetically encoded ratiometric sensors can be widely used for intracellular studies of various target analytes.

Intracellular pH plays a significant role in many pathological and physiological processes. A series of quinoline-pyrene probes were synthesized in one-step fashion through an oxonium-ion-triggered alkyne carboamination sequence involving C-C, C-O and C-N bond formation for intracellular pH sensing. The quinoline-pyrenes showed significant red shifts at low pH. Fluorescence lifetime decay measurements of the probes showed decreases in lifetime at pH 4. The probes showed excellent selectivity in the presence of various potential interfering agents such as amino acids and cations/anions. Furthermore, the probes were found to show completely reversible emission behaviour in the window between pH 4 and 7. A morpholine-substituted quinoline-pyrene probe efficiently stained lysosomes with high Pearson correlation coefficients (0.86) with Lysotracker Deep Red DND-99 as a reference. A co-localization study of the probe with Lysotracker DND-99 showed selective intracellular targeting and a shift in fluorescence emission due to acidic lysosomal pH., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal-organic frameworks (MOFs) with multiple emission centers are newly emerging as ratiometric sensors owing to their high sensitivity and high selectivity toward a wide range of targeted functional species. Energy transfer between the light-absorbing group and emission centers and between different emission centers is the key to rationally design and synthesize MOF-based ratiometric sensors. A good match between the energy levels of the light-absorbing groups and emission centers is the prerequisite for MOF-based sensors to exhibit multiple emissions, and a good match of the MOF-based sensors and those of the targeted species can increase the sensitivity and selectivity, but this match is highly challenging to obtain via synthesis. MOFs with multiple emission centers can be produced by functionalizing MOFs with multiple lanthanide centers, organic luminophores, dyes, carbon dots, and other such emissive groups. In this progress report, recent advances in the strategies for synthesizing MOFs with multiple emission centers and their applications for ratiometric sensing of solution conditions, including the pH value, and ion, organic molecule, and biomolecule concentrations, are summarized, as are the related sensing mechanisms., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mutants of human cellular retinol-binding protein II (hCRBPII) were engineered to bind a julolidine retinal analogue for the purpose of developing a ratiometric pH sensor. The design relied on the electrostatic influence of a titratable amino acid side chain, which affects the absorption and, thus, the emission of the protein/fluorophore complex. The ratio of emissions obtained at two excitation wavelengths that correspond to the absorption of the two forms of the protein/fluorophore complex, leads to a concentration-independent measure of pH., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work we investigate a mesoporous silica (MS) decorated with dipyridyl-pyridazine (dppz) ligands and further grafted with a mixture of Eu 3+ /Tb 3+ ions (28.45%:71.55%), which was investigated as a potential thermometer in the 10-360 K temperature range. The MS material was prepared employing a hetero Diels-Alder reaction: 3,6-di(2-pyridyl)-1,2,4,5-tetrazine was reacted with the double bonds of vinyl-silica (vSilica) followed by an oxidation procedure. We explore using the dppz-vSilica material to obtain visible emitting luminescent materials and for obtaining a luminescent thermometer when grafted with Eu 3+ /Tb 3+ ions. For the dppz-vSilica@Eu,Tb material absolute sensitivity S a of 0.011 K -1 (210 K) and relative sensitivity S r of 1.32 %K -1 (260 K) were calculated showing good sensing capability of the material. Upon temperature change from 10 K to 360 K the emission color of the material changed gradually from yellow to red., (Copyright © 2018 John Wiley & Sons, Ltd.)

Ratiometric MRI sensors consist of paramagnetic cores and pH-sensitive polymer shells. The core-shell nanostructure enables the coexistence of two incompatible NMR relaxation properties in one particle. The sensors show pH sensitivity in transverse relaxivity (r2 ), but not in longitudinal relaxivity (r1 ). Quantitative pH imaging is achieved by measuring the r2 /r1 value with a clinical 3 T MRI scanner., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)