Selective Optical Sensor Research Articles

A highly selective, colorimetric, and environment-sensitive optical potassium ion sensor.

Potassium ions (K+) play vital roles in many biological processes and thus highly selective sensors for K+ are critical for disease diagnosis and health monitoring. Herein, we report a colorimetric K+ sensor (KS7) in which a hemicyanine dye was used as a fluorophore and phenylaza-[18]crown-6 lariat ether (ACLE) was utilized as a K+ ligand. The maximum absorption peak of KS7 shifted hypsochromically by 77 nm (from 515 to 438 nm) with an isosbestic point at 452 nm upon the addition of K+ to its aqueous solution accompanied by a color change from red to yellow. This sensor exhibited a linear response range to K+ from 1 to 200 mM, indicating its wide detection range for cellular, urinary, and environmental potassium ions. Further, this sensor is solvent-sensitive, implying its environmental sensitivity. For the demonstration of its applications, we prepared filter paper-based K+ test strips, which were used to detect K+ in urine conveniently.

A selective and sensitive optical sensor for dissolved ammonia detection via agglomeration of fluorescent Ag nanoclusters and temperature gradient headspace single drop microextraction

In this paper, a simple sensor platform is presented for highly selective and sensitive detection of dissolved ammonia in aqueous solutions without pretreatment based on temperature gradient headspace single drop microextraction (HS-SDME) technique, and fluorescence and UV–vis spectrophotometry are utilized with the Ag nanoclusters (Ag NCs) functioned by citrate and glutathione as the probe. The sensing mechanism is based on the volatility of ammonia gas and the active response of Ag NCs to pH change caused by the introduction of ammonia. High pH can make the Ag NCs agglomerate and lead to the obvious decrease of fluorescence intensity and absorbance of Ag NCs solution. Moreover, the presented method exhibits a remarkably high selectivity toward dissolved ammonia over most of inorganic ions and amino acid, and shows a good linear range of 10–350μM (0.14–4.9mgNL−1) with a low detection limit of 336nM (4.70μgNL−1) at a signal-to-noise ratio of 3. In addition, the practical applications of the sensor have been successfully demonstrated by detecting dissolved ammonia in real samples.

Intensity-based plastic optical fiber sensor with molecularly imprinted polymer sensitive layer

For the detection of chemical agents in different environments, the combination of plastic optical fibers (POFs) and molecularly imprinted polymers (MIPs) receptors has been tested as a way to obtain low cost, highly selective and sensitive optical chemical sensors based on plasmonic resonance. In this work, a novel type of optical chemical sensor able to detect the binding reactions occurring between the MIP and analyte has been designed, fabricated and applied for the selective detection of dibenzyl disulfide (DBDS) in transformer oil. This analyte is important in the control of transformer oil, since it is responsible for the corrosive properties of the oil. The new optical sensor platform is based on two plastic optical fibers that work as segmented waveguides coupled through a polymer molecularly imprinted for the analyte. The prepolymeric MIP solution was deposited by drop coating in a trench milled between the two fibers. The experimental results indicated that this new sensor can be useful for the determination of DBDS in transformer oil and it paves the way to a new approach in the optical fiber sensors for MIPs.

Features of the use of optical reflection from thin porous silicon for detection of organic liquids

An express technique to define the thickness and rate of porous silicon (PS) layer growth during the electrochemical etching of silicon wafers is proposed. The method is based on the in situ measurement of reflected laser beam from PS layer in electrochemical cell during the etching process. Numerical simulation of the wavelength-dependent interference data obtained from the reflectivity showed the possibility of the selectivity improvement of thin layer PS sensors by the use of a set of PS layers with defined thicknesses and porosities. The different behavior of the reflection coefficients, shape and position of the maxima of the interference peaks during desorption of water-ethanol solutions and wines from the PS films were observed. The differences in the peak shape indicated the presence of inhomogeneity in the distribution of the film porosity with depth. On the other hand, the differences in the interaction modes between the adsorbed molecules and the pore surface caused differences in the kinetics of the optical characteristics during the desorption. The obtained results could be useful for development of selective optical sensors based on porous materials.

Development of a selective prilocaine optical sensor based on molecularly imprinted shell on CdTe quantum dots

A sensitive optical sensor, using a molecularly imprinted film on CdTe quantum dots (CdTe QDs), is developed for the selective detection of prilocaine. At the first step of this work, water-soluble thioglycolic acid capped CdTe QDs (TGA capped-CdTe QDs) were prepared using refluxing method. At the next step, a thin film of silica was formed, by reverse microemulsion technique, on the surface of CdTe quantum dots. Finally, molecularly imprinted polymer embedded CdTe QDs were obtained. In this step, 3-aminopropyltriethoxysilane (APTS) and tetraethoxysilane (TEOS) were applied as a functional monomer and a cross linker, respectively. Different variables affecting the optical signal were optimized. Under optimal conditions, the dynamic range of the optical sensor was 5.5–260.0nmolL−1 prilocaine with a detection limit as low as 0.6nmolL−1. The relative standard deviations of 5.3% and 7.5% for 126 and 35nmolL−1 prilocaine (n=3) were observed. The response of the optical sensor on common species in biological media was investigated. The results confirmed the good selectivity of the sensor for the measurement of prilocaine.

SBA-15 Functionalized with Naphthalene Derivative for Selective Optical Sensing of Cr2O7(2-) in Water.

A novel organic-inorganic hybrid optical sensor (NUS) was designed and prepared in two steps: the grafting of 3-(isocyanatopropyl)trimethoxysilane onto the surface of SBA-15, and then the attachment of naphthalene-1-amine. The obtained materials were characterized using low-angle XRD, N2 adsorption-desorption, TGA, FT-IR, and TEM techniques. A fluorescence study revealed that the NUS was a highly selective optical sensor for the detection of Cr2O7(2-) among various anions, including F(-), I(-), Cl(-), Br(-), CO3(2-), HCO3(-), NO3(-), H2PO4(-), CH3COO(-), and NO2(-) with a good linearity between the fluorescence intensity and the concentration of Cr2O7(2-) as well as a detection limit of 1.2 × 10(-7) M in a 100% aqueous medium. Moreover, the applicability of real samples of the sensor is also discussed.

A Highly Selective Sensor for Cyanide in Organic Media and on Solid Surfaces

The application of IR 786 perchlorate (IR-786) as a selective optical sensor for cyanide anion in both organic solution (acetonitrile (MeCN), 100%) and solvent-free solid surfaces was demonstrated. In MeCN, IR-786 was selective to two anions in the following order: CN− > OH−. A significant change in the characteristic dark green color of IR-786 in MeCN to yellow was observed as a result of nucleophilic addition of CN− to the fluorophore, i.e., formation of IR 786-(CN), which was also verified by a blue shift in the 775 nm absorbance peak to 430 nm. A distinct green fluorescence emission from the IR-786-(CN) in MeCN was also observed, which demonstrated the selectivity of IR-786 towards CN− in MeCN. Fluorescence emission studies of IR-786 showed that the lower detection limit and the sensitivity of IR-786 for CN− in MeCN was 0.5 μM and 0.5 to 8 μM, respectively. The potential use of IR-786 as a solvent-free solid state sensor for the selective sensing and monitoring of CN− in the environment was also demonstrated. On solvent-free solid state surfaces, the sensitivity of the IR-786 to CN− in water samples was in the range of 50–300 μM with minimal interference by OH−.

Biosensors Used for Quantification of Nitrates in Plants

Nitrogen is essential for the plant because it is used for the production of chlorophyll, proteins, nucleic acids, amino acids, and other cellular compounds; nitrogen is available in two forms: ammonium and nitrate. Several tools have been used to quantify nitrates in plants such as the Kjeldahl method and Dumas combustion digestion; however, they are destructive and long time-consuming methods. To solve these disadvantages, methods such as selective electrodes, optical sensors, reflectometers, and images based sensors have been developed; nonetheless, all these techniques show interference when carrying out measurements. Currently, biosensors based on genetic constructions, based on the response of promoter gene fused to Gene Fluorescent Protein (GFP), are gaining popularity, because they improve the accuracy of measurements of nitrate by avoiding the interference of carriers ion, high salt conditions, and other factors. The present review shows the different methods to quantify the nitrogen in plants; later, a biosensors perspective is presented, mainly focused on biosensors based on organism genetically modified. The review presents a list of promoter and reporter genes that could be used to develop different kind of sensors, and a perspective of sensors to measure quantitatively the nitrogen is presented.

A highly selective and sensitive acylhydrazone-based turn-on optical sensor for Al3+

The fluorescence turn-on probing of Al3+ in ethanol was realized by the utilization of a type of conjugated acylhydrazone-based compound.

A New Optical Sensor for Selective Monitoring of Nickel Ion Based on A Hydrazone Derivative Immobilized on the Triacetyl Cellulose Membrane

A new highly selective optical sensor was prepared by de-esterification of triacetyl cellulose transparent film and chemical immobilization of 1-acenaphthoquinone 1-thiosemicarbazone (L) on it. The absorbance variation of immobilized 1-acenaphthoquinone 1-thiosemicarbazone on hydrolyzed cellulose acetate film of upon addition of 1.5 × 10-5 mol L-1 aqueous solutions of Zn2+, Pb2+, K+, Cu2+, Ag+, Ni2 , Cd2+, Ca2+, CrO4 2-, Hg2+, Co2+, Mn2+, Cr3+, S2 O3 2-, Mg2+, Na+, Al3+, Tl+ and Fe3+ indicated a substantiality much larger variation for the Nickel ion in compare to other studied ions. Consequently, the new hydrazone derivative L possesses a high selectivity towards this metal ion. Influences of various experimental parameters on Ni2+ sensing, including the reaction time, the solution pH and the concentration of reagents were studied. A linear relationship was observed between the variance in membrane absorbance(∆A) at 337 nm and Ni2+ concentrations in a range from 5.01 × 10-10 to 2.04 × 10-5 mol L-1 with a detection limit (3σ) of 1.00 × 10-10 mol L-1. No significant interference from 100 times concentrations of a number of potentially interfering ions was detected for the nickel ion determination. The sensor showed a good durability and short response time with no evidence of reagent leaching. The optical sensor was successfully applied to the determination of nickel in real water samples.

A new optical sensor for selective quantitation of uranium by the immobilization of arsenazo III on an agarose membrane

A highly selective optical sensor was introduced for the determination of UO22+ through the chemical immobilization of arsenazo III on a transparent agarose membrane.

A wavelength selective application for an optical fiber surface plasmon resonance sensor

In this paper, a wavelength selective optical fiber surface plasmon resonance sensor, which provides a flexible detection capability, has been experimentally investigated. The light reflected from the sensor tip in response to flowing water and ethanol are monitored at several single wavelengths. The reflected light transient modulated by flowing solvent has an exponential form, which the change in magnitude and response time are dependent on the monitoring wavelength. Optimal wavelength best suited for measurement was determined by investigating the dynamic response curve. Rather than wavelength and angular interrogation methods commonly used in SPR measurement, this single wavelength monitoring scheme is a low-cost, flexible and reliable method.

Schiff Base Impregnated Plasticized Polyvinyl Chloride Optical Sensor for Selective and Efficient Detection of Copper (II) Ion: Central Composite Design

In this paper, a novel selective, sensitive, and reversible copper (II) ion optical sensor was prepared based on the impregnation of N, $\text{N}{}^{\prime }$ -bis (2-hydroxynaphthaldehyde)-1, and 3-phenylenediimine (HNPD) into plasticized polyvinyl chloride (PVC) film. The optimal values of pH and response time at which the maximum performance of prepared optical sensor is achieved were found to be 6 and 2 min, respectively. After the optimization of pH and response time, small central composite design (CCD) and desirability function were applied to evaluate the effects of variables including amount of dibuthylphthalate, anion excluder (sodium tetraphenylborate), PVC, and HNPD content on the sensor as figures of merit. The possible interactions between the variables were also investigated using the CCD. Low detection limit and good selectivity in presence of other ions such as Fe3+, Ag2+, Cr3+, Zn2+, Hg2+, and SO42− make it feasible to accurately and repeatedly monitor Cu2+ ions content in real samples with complicated matrices. The optode was successfully regenerated by its exposure in 0.1 mol/L of ethylenediaminetetraacetic acid solution while its response was reversible with the relative standard deviation lower than 1.5%. This optode was stable and stored for at least 17 days without observing any change in its sensitivity.

Lanthanum (III) Ion Determination by a New Design Optical Sensor

A new selective and sensitive Lanthanum (La) ions optical sensor based on immobilization of N-(2-aminoethyl)-salicylaldimine (AESI) on a triacetylcellulose membrane was prepared. The prepared optode exhibited a linear range of 30-150 part per billion (ppb) of the La (III) ion concentration with a detection limit of 14.38 ppb. The response time of the newly designed optode was derived within 30-60 s, depending on the La (III) ion concentration, however is independent to the pH of the solution in the range of 3-5. The proposed optode indicated a low detection limit, fast response time, and also remarkable selectivity regarding to the number of transition metals ions (i.e. Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Cd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , Zn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , and Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ). The optode was successfully regenerated with a thiourea solution, and its response which might be reversible and reproducible showed the relative standard deviation of less than 1.48%. This optode was applied for determining the La (III) ions in water samples.

Design of a highly sensitive and selective bulk optode based on fluorescence enhancement of N,N′-bis-(1-hydroxyphenylimine)2,2′-pyridil Schiff base: Monitoring of zinc(II) ion in real samples and DFT calculation

A novel highly sensitive and selective optical chemical sensor (optode) was fabricated for the determination of Zn2+ ion. The optical sensor was prepared by incorporating recently synthesized ionophore, HPP: N,N′-bis-(1-hydroxyphenylimine)2,2′-pyridil, sodium tetraphenylborate (NaTPB) as an anionic additive, dibutyl phthalate (DBP) as a plasticizer in a poly(vinylchloride) membrane. The novel ionophore was synthesized by conventional condensation reaction between 2,2′-pyridil and 2-aminophenol and characterized using different spectroscopic techniques. The response of the sensor is based on the strong fluorescent emission enhancement of ionophore HPP upon binding to Zn2+ ions. This can be correlated to the efficient Zn2+ binding of HPP which promotes a good chelation-enhanced fluorescence (CHEF) effect and prevents the photoinduced electron transfer (PET) effect. The effect of several parameters in determining Zn2+ were studied and optimized. Under the optimum conditions, a good linear relationship between the fluorescence response and concentration of Zn2+ was achieved with high sensitivity within a wide range from 1.0×10−10 to 1.0×10−2M and a limit of detection (LOD) 6.3×10−11M. Furthermore, the present probe exhibited a high selectivity for Zn2+ over other metal ions and was successfully assessed for determination of Zn2+ ions in real samples including some food and biological samples with satisfactory results. Theoretical calculations were employed to support the sensing mechanism of the sensor toward Zn2+.

Multicolor Emitting Block Copolymer-Integrated Graphene Quantum Dots for Colorimetric, Simultaneous Sensing of Temperature, pH, and Metal Ions

Highly selective optical sensors that are capable of detecting complex stimuli have attracted significant interest in environmental, biomedical, and analytical chemistry applications. In this Article, we report the development of novel and versatile platform for highly efficient, colorimetric multifunctional sensors using block copolymer-integrated graphene quantum dots (bcp-GQDs). In particular, the multisensing behavior is successfully generated simply by grafting blue-emitting, temperature-responsive block copolymers onto green-emitting, 10 nm size GQD that provides luminescent response to pH changes. Thus, the bcp-GQDs showed simultaneous, orthogonal sensing behavior to temperature and pH, as well as dose-dependent responses to different types of metal ions. In addition, the bcp-GQD sensor showed excellent reversibility and dispersion stability in pure water, indicating that our system is an ideal platform for environmental and biological applications. The detailed mechanism of the responsive behavior of the bcp-GQDs was elucidated by measurements of time-resolved fluorescence and dynamic light scattering.

A Novel Naphthalene-Immobilized Nanoporous SBA-15 as a Highly Selective Optical Sensor for Detection of Fe(3+) in Water.

A novel organic-inorganic hybrid optical sensor (SBA-NCO) was designed and synthesized through immobilization of isocyanatopropyl-triethoxysilane and 1-amino-naphthalene onto the surface of SBA-15 by post-grafting method. The characterization of materials using XRD, TEM, N2 adsorption-desorption, and FT-IR techniques confirmed the successful attachment of organic moieties and preserving original structure of SBA-15 after modification step. Fluorescence experiments demonstrated that SBA-NCO was a highly selective optical sensor for the detection of Fe(3+) directly in water over a wide range of metal cations including Na(+), Mg(2+), Al(3+), K(+), Ca(2+), Cr(3+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+),and Pb(2+) in a wide pH values.

A nanostructured LUS-1 based organic–inorganic hybrid optical sensor for highly selective sensing of Fe3+ in water

An organic–inorganic hybrid optical sensor (LQS) was prepared with post grafting of 8-hydroxy-5-quinoline sulfonic acid onto the surface of LUS-1. Its structure was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR), N2 adsorption/desorption, and thermogravimetry analysis (TGA). The fluorescence evaluation of LQS toward a wide range of cations including Na+, Mg2+, Al3+, K+, Ca2+, Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ revealed that LQS was a highly selective optical sensor for Fe3+ in a wide range of pH in pure water.

Rapid synthesis of highly stable silver nanoparticles and its application for colourimetric sensing of cysteine

A modified green approach for the synthesis of stable silver nanoparticles (AgNPs) using tea leaf extract is described. The method involves the reduction of silver salt by the polyphenols present in the green tea leaf extract and requires no additional capping/stabilising agents. Compared to other biogenic methods for the synthesis of AgNPs, the uniqueness of the approach described here lies in its simplicity, low-cost, and rapid synthesis rate; the reaction being completed within 10–15 min at room temperature. The reaction was carried out in alkaline medium without stirring and heating, and requires no special cleaning or drying of the glassware used. The synthesised AgNPs were characterised by UV–Vis spectroscopy and transmission electron microscopy (TEM). The results showed that AgNPs with a strong surface plasmon resonance peak around 410 nm and particle size in the 5–30 nm range were prepared. The synthesised AgNPs show excellent chemical stability for more than six months in aqueous solution. Additionally, we showed that the as-synthesised AgNPs can be used as highly selective colorimetric and optical sensors for the detection of cysteine. Thus, with a simple synthesis strategy, and enhanced stability, these green-tea-functionalised AgNPs have the potential for further applications as biosensors and antimicrobial agents.

A highly selective fluorescent sensor for glucosamine.

A new fluorescent chemical sensor for glucosamine is reported. The sensor is based on a boronic acid-containing coumarin aldehyde and shows excellent selectivity for glucosamine by forming a boronic ester with the sugar diol as well as an iminium ion with the amine group of glucosamine. The sensor successfully discriminates glucosamine over other similar biomolecules in terms of both fluorescence intensity and binding affinity. This method provides a new concept for the design and synthesis of very selective turn-on optical sensors for selective detection of multi-functional biomolecules.