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The development of fluorophores emitting in the near-infrared spectral window has gained increased attention given their suitable features for biological imaging. In this work, we have optimised a general and straightforward synthetic approach to prepare a small library of near-infrared-emitting C-bridged nitrobenzodiazoles using commercial precursors. C-bridged benzodiazoles have low molecular weight and neutral character as important features that are not common in most near-infrared dyes. We have investigated their fluorescence response in the presence of a wide array of 60 different biomolecules and identified compound 3i as a potential chemosensor to discriminate between Fe2+ and Fe3+ ions in aqueous media.

In this study, a novel 1,10-phenanthroline skeleton-based fluorescence chemosensor (IPN) was prepared and applied to investigate the metal ions sensing properties. The sensor exhibited an exceptional selective fluorescence response toward Ni2+ combined with the characteristic of high sensitivity, excellent specificity and fast response. The IPN-Ni2+ complex was formed in the ratio of IPN/Ni2+ of 1/2. Introduction of Ni2+ induced the change of fluorescence emission spectra of IPN at 340 nm and 392 nm. Based on Job diagram analysis, frontier molecular orbital calculation and infrared spectrum analysis, the possible mechanism of fluorescence detection Ni2+ was proposed. Moreover, the cell imaging using IPN indicates that IPN is expected to be a useful probe for Ni2+ in broad biological application.

Two novel rhodamine-based polystyrene solid-phase fluorescence sensors PS-PA-I and PS-PA-II with different lengths of polyamines were synthesized for Hg(II) determination. The detection mechanism involving the Hg(II) chelation-induced spirocycle open of rhodamine was proposed with the aid of theoretical calculation. The stronger N—Hg bond and the longer polyamine chain in PS-PA-II led to a better selectivity, much higher and more quickly fluorescence response to Hg(II).

A boronic acid-based anthracene fluorescent probe was functionalised with an acrylamide unit to incorporate into a hydrogel system for monosaccharide detection. In solution, the fluorescent probe displayed a strong fluorescence turn-on response upon exposure to fructose, and an expected trend in apparent binding constants, as judged by a fluorescence response where d–fructose > d–galactose > d–mannose > d–glucose. The hydrogel incorporating the boronic acid monomer demonstrated the ability to detect monosaccharides by fluorescence with the same overall trend as the monomer in solution with the addition of d–fructose resulting in a 10-fold enhancement (⩽ 0.25 mol/L).

Hydrogen sulfide (H2S) has recently been recognized as the third endogenous gaseous signaling molecule besides NO and CO. At the same time, H2S is responsible for an important proportion of faulty wines with potentially large economic losses. Thus, the H2S in wine not only contributes negatively to wine aroma but also faces a problem of food safety. So an efficient and practical sensor to detect H2S in wine was needed. A new fluorescent probe 4-methyl-2-oxo-2H-chromen-7-yl-thiophene-2-carboxylate (probe 1) was designed and synthesized for detection of H2S. Addition of H2S caused the fluorescence intensity of probe 1 increased and fluorescence saturation was reached in 15 min. The fluorescence of probe 1 was found turn-on under UV light at 365 nm. This noticeable change of probe 1 indicates that probe 1 could be employed as a visible detection agent for H2S. H2S can be detected quantitatively in the concentration range 0–20 μM, and the detection limit on fluorescence response of the probe was 18 nM. Moreover, probe 1 can be conveniently used as a signal tool to determine the H2S levels in wine.

A novel fluorescein-based dual probe was designed and synthesized. The probe exhibited highly sensitive and selective colormetric response to Fe3+ and turn-on fluorescence response towards OCl− with very low detection limits of 100 and 50 nM, respectively. It was successfully applied for quantitative detection of Fe3+ and OCl− in real water samples. Moreover, probe 1 was expected to be a potentially powerful tool for studying and providing further insights into OCl− and Fe3+ chemistry in the near future.

A new rhodamine-based fluorescent chemosensor (1) has been designed and synthesized by linking rhodamine 6G hydrazide with N-methylisatin via an imine linkage. The receptor can selectively recognize and sense Pb2+, Hg2+ and Cd2+ by showing different fluorescence characteristics. In ethanol/HEPES buffer medium, the addition of Cd2+ caused a yellowish-green fluorescence, while the presence of Pb2+ or Hg2+ gave rise to an orange fluorescence. Additionally, the sensor shows an irreversible fluorescence response to Pb2+ and reversible fluorescence responses to Hg2+ and Cd2+.

A new bi-functional chemosensor 1 based on 3,5-dichlorosalicylaldehyde and 2-(methylthio)aniline has been synthesized. It can detect Cu2+ with a color change from pale yellow to dark yellow in aqueous solution. The selective mechanism of 1 for Cu2+ was proposed to be the enhancement of the intramolecular charge transfer (ICT) band, which was explained by theoretical calculations. The sensor 1 could be used to detect and quantify Cu2+ in water samples. In addition, the sensor 1 displayed "turn-on" fluorescence response only to Zn2+, based on an effect of chelation-enhanced fluorescence (CHEF). Therefore, 1 can serve as a 'single sensor for two different targets' with dual modes.

Molecularly imprinted polymers (MIPs) are potent and established recognition phases in separation and enrichment applications. Because of their robustness, versatility and format adaptability, they also constitute very promising sensing phases, especially when the active sensing element is directly integrated into the MIP. Fluorescent MIPs incorporating fluorescent monomers are perhaps the best developed and most successful approach here. This article reviews the state of the art in this field, discussing the pros and cons of the use of fluorescent dye and probe derivatives as such monomers, the different molecular interaction forces for template complexation, signalling modes and a variety of related approaches that have been realized over the years, including Förster resonance energy transfer processes, covalent imprinting, postmodification attachment of fluorescent units and conjugated polymers as MIPs; other measurement schemes and sensing chemistries that use MIPs and fluorescence interrogation to solve analytical problems (fluorescent competitive assays, fluorescent analytes, etc.) are not covered here. Throughout the article, photophysical processes are discussed to facilitate understanding of the effects that can occur when one is planning for a fluorescence response to happen in a constrained polymer matrix. The article concludes with a concise assessment of the suitability of the different formats for sensor realization.

Flow-injection analysis is proposed for routine measurement of Maillard-derived Xuorescent compounds (FC) in cookies as a marker of the extent of baking. In addition, procedure was applied to investigate the formation of free and total (bound to protein free) FC in cookie-resembling models and in commercial wheat-based cookies as well. FC accounts for the overall Xuorescence response of Maillard-derived Xuorescent compounds (bound or not to protein) formed during baking but not for a single compound. Free and total FC values increased exponentially during baking at 200, 210 and 220 °C and an induction period of 10 min was observed for free FC. In the complex scenario of the progress of the Maillard reaction (MR) during baking, formation of FC (347/415, ext/emm) was not the limiting step for browning development at the advanced stage of the reaction. Furthermore, the formation of Maillard-derived Xuorescent compounds and browning during baking were a consequence of parallel reactions apart from the classical MR scheme of consecutive reactions. Total/free FC ratio was dependent on the baking conditions applied and ratio was signiWcantly decreased at severe baking conditions. Total/free FC ratio could be used as a reference marker for monitoring the process and to identify potential over-processing situations during baking. In addition, Xuorescent residues were originally bound to protein because total/free FC ratio decreased drastically as increased the temperature and time of the process. Levels of total FC were nearly 20-fold of free FC in commercial samples. Values of FC were positively correlated with acrylamide, a Maillard-derived food processing contaminant. © Springer-Verlag 2009.

Low temperature is one of the major environmental factors determining the growth rate ofCamellia sinensis (L.), and photosynthesis is one major metabolic process commonly used as a tool for identifying low temperature stress effects on plants. The Fv/Fm values at 6:30 a.m. (300-400 umol m-2s-1) did not vary much between the clones of tea plants. Further, when the light incidence increased at mid noon hours (1700-1800 µmol m-2s-1), the Fv/Fm values recorded a decline, irrespective of the clones. Of the 10 clones of tea plants under investigation, 3 clones, namely CRA-6017, TTL-6 and SMP-1, recorded a sharp decrease in the Fv/Fm ratio by 2 p.m. The malondialdehyde (MDA) levels in all the clones increased from 9 a.m. (1500-1700 µmol m-2s-1) to 2 p.m. and from 4:30 p.m. (900-1100 µmol m-2s-1) onwards it started to decrease and reach the levels equivalent to 6:30 a.m. by 7 p.m. (5–10 µmol m-2s-1 ). But the clones of TTL-1, TTL-4 and UPASI-9 showed low temperature tolerance as appeared in chlorophyll a fluorescence response. They showed a higher percentage increase in MDA levels, as compared to TTL-6, CRA-6017 and SMP-1, which showed low temperature susceptibility. But the reduction in the level of MDA by 4:30 p.m. (recovery) was faster in the clones TTL-1, TTL-4 and UPASI-9, as compared to TTL-6, SM/OM/54 and SMP-1. The result indicates that in TTL-6, SMP-1 and SM/ OM/54, the toxic oxygen species scavenging mechanisms may be less functional as compared to other clones. The percentage increase of proline and carotenoids was higher in clones TTL-1, TTL-4 and UPASI-9 as compared to TTL-6, CRA-6017 and SMP-1.

Time-resolved fluorescence spectroscopy and microscopy in both time and frequency domains provide very useful and accurate information on dynamic processes. Good quality data are essential in obtaining reliable parameter estimates. Distortions of the fluorescence response due to artifacts may have disastrous consequences. We provide here a concise overview of potential difficulties encountered under daily laboratory circumstances in the use of time- and frequency-domain equipment as well as practical remedies against common error conditions, elucidated with several graphs to aid the researcher in visual inspection and quality-control of collected data. A range of artifacts due to sample preparation or to optical and electronic pitfalls are discussed, as are remedies against them. Also recommended data analysis strategies are described.

This review provides a chronological survey of over fifty fluorescent chemosensors for carbohydrates from the period between 1992 to the present. The survey contains only those sensors that are synthetic or chemosensory, utilize boronic acids and display a fluorescence response in the form of intensity changes or shifts in wavelength. With each compound listed, a description of the saccharide probe is given with regard to concentration, excitation and emission wavelengths, pH and solvent mixture proportions. In addition, the selectivity of each chemosensor is provided as well as the trends in binding constants. Where possible, a description of the fluorescence signaling mechanism is given as well as commentary on the probe's unique features within this class of sensors.

A new class of reagentless optical biosensors are emerging based on the use of engineered proteins that are site-selectively labelled with a fluorescent reporter group. Such sensors can operate either by direct interaction of the analyte with the bound probe, or by generating a fluorescence response to an analyte induced conformational change in the protein. In this review, the preparation, characterization and use of fluorescently labelled proteins for the development of reagentless optical biosensors is described. Recent work involving the rational design of fluorescent protein biosensors, and efforts at characterizing the origins of responses from these systems is highlighted. An overview of the recent and potential future trends in this area is also given. Finally, methods of immobilizing such biomolecules for the development of reuseable sensors are described.