As in many other methods that have integrated nanoparticles (NPs), the chemical nose/tongue strategy has also progressed greatly since the entrance of NPs into this field. The fascinating tunable ...physicochemical properties of NPs have made them powerful candidates for array-based sensing platforms and have enabled the development of real-time, sensitive and portable systems that are able to target complex mixtures of analytes. In particular, the unique optical properties of NPs have a key role in providing promising array-based sensing approaches. This review will describe the main aspects and processes of most common NP-based optical sensor arrays. The fundamental steps in the design of a sensor array together with details of each step would be provided. The review begins with the principles of optical sensor arrays and presents the concept of cross-reactivity as the main criterion in the selection of sensing elements. Changes in the absorption and emission properties of the assembled sensing elements are categorized into two main classes of optical signals (colorimetric and fluorometric). Popular chemometric methods used for analyzing the data acquired by a sensor array have also been briefly introduced. On the basis of the objective and the desired application, different types of plasmonic and fluorescent NP that possess unique opto-physical properties have been presented as available choices in the design of sensing elements. The vast number of applications of NP-based optical sensor arrays published throughout the literature have then been reviewed according to their mechanism of interaction and the type of optical signal. Finally, the remaining challenges and future directions in this topic have been highlighted.
Recent progress in nanoparticle-based optical sensor arrays toward the detection and discrimination of a wide range of analytes.
Signal generation techniques for visual detection of analytes have received a great deal of attention in various sensing fields. These approaches are considered to be advantageous when ...instrumentation cannot be employed, such as for on-site assays, point-of-care tests, and he althcare diagnostics in resource-constrained areas. Amongst various visual detection approaches explored for non-invasive quantitative measurements, ratiometric fluorescence sensing has received particular attention as a potential method to overcome the limitations of intensity-based probes. This technique relies on changes in the intensity of two or more emission bands (induced by an analyte), resulting in an effective internal referencing which improves the sensitivity of the detection. The self-calibration, together with the unique optophysical properties of nanoparticles (NPs) have made the ratiometric fluorescent nanoprobes more sensitive and reliable, which in turn, can result in more precise visual detection of the analytes. Over the past few years, a vast number of ratiometric sensing probes using nanostructured fluorophores have been designed and reported for a wide variety of sensing, imaging, and biomedical applications. In this work, a review on the NP-based ratiometric fluorescent sensors has been presented to meticulously elucidate their development, advances and challenges. With a special emphasis on visual detection, the most important steps in the design of fluorescent ratiometric nanoprobes have been given and based on different classes of analytes, recent applications of fluorescent ratiometric nanoprobes have been summarized. The challenges for the future use of the technique investigated in this review have been also discussed.
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•Ratiometric fluorescent nanoprobes are known as promising sensing tools.•Ratiometric probes provide distinguishable color changes for visual detection.•The internal referencing in ratiometric probes greatly enhances their sensitivity.•Visual detection is helpful for onsite monitoring in resource-constrained areas.•Ratiometric design requires rational manipulation of nanostructured fluorophores.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Owing to its dual role as a hormone and neurotransmitter, norepinephrine (NE) detection is of great significance to biomedical diagnosis. In the present work, we have explored intense green ...fluorescence of poly (norepinephrine) (PNE) nanoparticles synthesized by oxidizing NE in alkaline condition, in combination with red fluorescent bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) for naked-eye detection of NE. The effect of sodium hydroxide on the emission behavior of NE was studied. The surface morphology and optical properties of PNE nanoparticles were characterized by UV–Vis, fluorescence, FTIR, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. For ratiometric sensing of NE, red fluorescent BSA-AuNCs were served as an internal reference while NE delivered a new emission peak at 527 nm, resulting in a wide distinguishable color change from strong red into red, pink, orange, and green under a UV lamp. The ratiometric approach was demonstrated to be highly sensitive and selective for NE detection against even structurally similar biomolecules with a detection limit of 49 nmol L−1. Furthermore, the proposed method was successfully applied to determine NE in urine samples.
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•The oxidation product of norepinephrine has intense green fluorescence.•A naked-eye ratiometric fluorescence method has been developed for norepinephrine detection.•Different concentrations of norepinephrine were identified by color changes from red to green.•High selectivity was achieved without the interference of structurally similar molecules.•A simple and low-cost sensor has been presented for norepinephrine detection in urine samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A simple and effective ratiometric fluorescence sensor for selective detection of dopamine (DA) in alkaline media has been developed by simply mixing thioglycolic acid (TGA) functionalized orange ...fluorescent cadmium telluride (CdTe) quantum dots (QDs) with amino-functionalized blue fluorescent carbon nanodots (CDs). Under a single excitation wavelength of 365 nm, the sensor exhibits dual-emissions centered at 445 and 603 nm. The fluorescence of CdTe QDs is selectively quenched by DA, whereas the fluorescence of CDs is insensitive to the analyte. In the presence of different amounts of DA, the variations in the dual emission intensity ratios exhibit a continuous color change from pink to purple and to blue, which can be clearly observed with the naked eye. The ratiometric fluorescent probe has been successfully applied for the detection of DA in water and urine with a detection limit of 1.3 μM. To facilitate their practical use, ratiometric fluorescent probe–agarose hydrogels were prepared as instrument-free and simple platforms for visual detection of DA.
•A simple and fast fluorescence approach was developed for visual detection of sulfide.•Fluorescence probe consists of blue emissive carbon dots and orange emissive gold nanoclusters.•The probe was ...successfully applied for sulfide detection in river and spring water.•The visual limit of detection of 4 µM is obtained.
Development of visual detection methods regarding water pollutants can effectively facilitate water resource monitoring programs. A wide color-varying ratiometric approach has been developed for sensitive determination of sulfide by mixing orange emissive glutathione stabilized gold nanoclusters (AuNCs) and blue emissive urea stabilized carbon dots (CDs) in an appropriate ratio. Under a single excitation wavelength of 365 nm, the ratiometric fluorescence (RF) probe exhibited two distinct emission bands at 452 and 607 nm corresponding to CDs and AuNCs, respectively. Owing to the high affinity of sulfide ions to AuNCs in alkaline medium, the fluorescence (FL) of AuNCs was turned-off while the emission of CDs remained unchanged, resulting in a distinguishable FL color change from pink to blue under an ultra-violet (UV) lamp. The I452/I607 ratio was linearly dependent to sulfide concentration in the range of 1.0 to 50.0 µM with a limit of detection (LOD) of 0.35 µM and a visual LOD as low as 4.0 µM that is less than the maximum allowable sulfide amount (10.0 µM) in drinking water. The RF probe was successfully applied for further determination of sulfide in river water and acceptable recoveries were obtained. We believe that the simplicity together with the great visual capability of this visual RF probe can improve and facilitate on-site sulfide determination.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A simple and effective ratiometric fluorescence sensor for selective detection of dopamine (DA) in alkaline media has been developed by simply mixing thioglycolic acid (TGA) functionalized orange ...fluorescent cadmium telluride (CdTe) quantum dots (QDs) with amino-functionalized blue fluorescent carbon nanodots (CDs). Under a single excitation wavelength of 365 nm, the sensor exhibits dual-emissions centered at 445 and 603 nm. The fluorescence of CdTe QDs is selectively quenched by DA, whereas the fluorescence of CDs is insensitive to the analyte. In the presence of different amounts of DA, the variations in the dual emission intensity ratios exhibit a continuous color change from pink to purple and to blue, which can be clearly observed with the naked eye. The ratiometric fluorescent probe has been successfully applied for the detection of DA in water and urine with a detection limit of 1.3 μM. To facilitate their practical use, ratiometric fluorescent probe-agarose hydrogels were prepared as instrument-free and simple platforms for visual detection of DA.
A simple and effective ratiometric fluorescence sensor for selective detection of dopamine (DA) in alkaline media has been developed by simply mixing thioglycolic acid (TGA) functionalized orange fluorescent cadmium telluride (CdTe) quantum dots (QDs) with amino-functionalized blue fluorescent carbon nanodots (CDs).
