Harnessing a Ratiometric Fluorescence Output from a Sensor Array

Fluorimetric sensing of ATP in water by an imidazolium hydrazone based sensor

Bisantrene, a simple anthracene derivative carrying two imidazolium hydrazone moieties, has been used as a highly selective sensor of ATP in water.

Ratiometric Fluorescent Sensor Array as a Versatile Tool for Bacterial Pathogen Identification and Analysis

Rapid and reliable identification of pathogenic microorganisms is of great importance for human and animal health. Most conventional approaches are time-consuming and require expensive reagents, sophisticated equipment, trained personnel, and special storage and handling conditions. Sensor arrays based on small molecules offer a chemically stable and cost-effective alternative. Here we present a ratiometric fluorescent sensor array based on the derivatives of 2-(4'- N, N-dimethylamino)-3-hydroxyflavone and investigate its ability to provide a dual-channel ratiometric response. We demonstrate that, by using discriminant analysis of the sensor array responses, it is possible to effectively distinguish between eight bacterial species and recognize their Gram status. Thus, multiple parameters can be derived from the same data set. Moreover, the predictive potential of this sensor array is discussed, and its ability to analyze unknown samples beyond the list of species used for the training matrix is demonstrated. The proposed sensor array and analysis strategies open new avenues for the development of advanced ratiometric sensors for multiparametric analysis.

Novel fluorescent anthracene–bodipy dyads displaying sensitivity to pH and turn-on behaviour towards Cu(ii) ions

The effect of the nature of the spacer in three new bichromophoric compounds showing intramolecular PET and EET processes has been studied.

Highly selective colorimetric and fluorescent detection for Hg2+ in aqueous solutions using a dipeptide-based chemosensor

A dipeptide-based chemosensor selectively and sensitively detected Hg^II in aqueous solutions by colorimetric change and fluorescent change.

Highly sensitive colorimetric detection of HgII and CuII in aqueous solutions: from amino acids toward solid platforms

A chemosensor (NBD-H) based on an amino acid with 7-nitro-2,1,3-benzoxadiazole was used for selective detection of Hg^II and Cu^II among 15 metal ions in aqueous solutions by a colorimetric change and fluorescence change.

Rapid identification of bacterial biofilms and biofilm wound models using a multichannel nanosensor

Identification of infectious bacteria responsible for biofilm-associated infections is challenging due to the complex and heterogeneous biofilm matrix. To address this issue and minimize the impact of heterogeneity on biofilm identification, we developed a gold nanoparticle (AuNP)-based multichannel sensor to detect and identify biofilms based on their physicochemical properties. Our results showed that the sensor can discriminate six bacterial biofilms including two composed of uropathogenic bacteria. The capability of the sensor was further demonstrated through discrimination of biofilms in a mixed bacteria/mammalian cell in vitro wound model.

Fluorescent nanohybrid of gold nanoclusters and quantum dots for visual determination of lead ions

Highly green emissive gold nanoclusters (Au NCs) are synthesized using glutathione as a stabilizing agent and mercaptopropionic acid as a ligand, and the intensity of fluorescence is specifically sensitive to lead ions. We then fabricated a ratiometric fluorescence nanohybrid by covalently linking the green Au NCs to the surface of silica nanoparticles embedded with red quantum dots (QDs) for on-site visual determination of lead ions. The green fluorescence can be selectively quenched by lead ions, whereas the red fluorescence is inert to lead ions as internal reference. The different response of the two emissions results in a continuous fluorescence color change from green to yellow that can be clearly observed by the naked eyes. The nanohybrid sensor exhibits high sensitivity to lead ions with a detection limit of 3.5 nM and has been demonstrated for determination of lead ions in real water samples including tap water, mineral water, groundwater, and seawater. For practical application, we dope the Au NCs in poly(vinyl alcohol) (PVA) film and fabricate fluorescence test strips to directly detect lead ions in water. The PVA-film method has a visual detection limit of 0.1 μM, showing its promising application for on-site identification of lead ions without the need for elaborate equipment.

Differentiation of Functional Groups and Biologically Relevant Anions Using AT-PAMAM Dendrimers

Biological anions have often proven to be difficult analytes to differentiate in solution. Many of the anions bear similar structural characteristics and similar charge states. Using a commercially available indicator and AT-PAMAM dendrimers, a sensing ensemble for a number of biological anions was constructed. The system was able to identify each of the different analytes as well as the regioisomers of three different tricarboxylates. The system shows responsiveness to not only functional group identity but also the charge state and identity of the anionic species.

Photoinduced electron transfer (PET) based Zn2+ fluorescent probe: transformation of turn-on sensors into ratiometric ones with dual emission in acetonitrile

Ratiometric sensors for the detection of metal ions have gained increasing attention due to its self-calibration tendency for the environmental effects. In this context, we have synthesized and characterized a dual emitting ratiometric Zn(2+) probe (1) having acridinedione as a fluorophore and N,N-bis(2-pyridylmethyl)amine (BPA) as a receptor unit. Existence of two different conformation of the molecule with photoinduced electron transfer (PET) from amine moiety to the acridinedione fluorophore leads to dual emission, namely locally excited (425 nm) and anomalous charge transfer emission (560 nm) in aprotic solvents. In the presence of one equivalent of Zn(2+), a 15-fold fluorescence enhancement in the locally excited state together with the quenching of charge transfer emission is observed. The intensity changes at the two emission peaks allow a ratiometric detection of Zn(2+) under PET signaling mechanism. The utilization of PET process for the ratiometric fluorescence change will further signify the importance of PET mechanism in sensing action. Addition of Zn(2+) to 1 in acetonitrile/water mixtures shows a single emission peak with fluorescence enhancement.

Dual fluorescence self-assembled multilayers bearing a fluorescent internal standard for interfacial sensing

A novel dual fluorescence film Quartz/PSS/AO/PSS/CS/CdTe sensor was constructed based on layer-layer electrostatic attraction using CdTe as a fluorescence probe. Acridine orange is shielded effectively by sodium poly(4-styrenesulfonate) and chitosan, thus its fluorescence intensity does not change in the presence of the analyte, thereby acting as a fluorescent internal standard providing a reference signal. The ratio of dual fluorescence intensities of the film sensor is not affected by the fluctuation of the external environment factors such as excitation intensity, detector voltage of photo multiplier tube and sensor position in the cell holder. Assays based on this dual fluorescence self-assembled multilayers sensor afforded an extremely high sensitivity for DNA with greatly accuracy.

The power of the weak: recognition of ion pairs in water using a simple array sensor

Thirty-five different ion pairs are recognized by a sensor array consisting of supramolecular hydrogel and six off-the-shelf pH indicators at pH = 5–9. Such recognition efficiency (6 : 35) with ≥93% classification accuracy is rare.