Utilization of a plasticized PVC optical sensor for the selective and efficient detection of cobalt(ii) in environmental samples

Ultrasensitive optical fiber SPR sensor enhanced by Au-NPs-film modified with functionalized CQDs for label-free detecting cobalt (II) ion

BACKGROUND

Cobalt, an essential trace element, is vital for maintaining human nervous system function, aiding in DNA synthesis, and contributing to red blood cell production. It is helpful for disease diagnosis and treatment plan evaluation by precisely monitoring its concentration changes in the human body. Despite extensive efforts made, due to its ultra-low concentration, the current limit of detection (LOD) as reported is still inadequate and cannot be satisfied with the precise clinical applications. Therefore, it is crucial to develop novel label-free sensors with high sensitivity and excellent selectivity for detecting trace amounts of Co2+.

RESULTS

Here, an ultrasensitive optical fiber SPR sensor was designed and fabricated for label-free detection of Co2+ with ultra-low concentration. It is achieved by modifying the carboxyl-functionalized CQDs on the AuNPs/Au film-coated hetero-core fiber, which can specifically capture the Co2+, leading to changes in the fiber's surface refractive index (RI) and subsequent SPR wavelength shifts in the transmission spectrum. Both the Au film and AuNPs on the fiber are modified with CQDs, leveraging their large surface area to enhance the number of active sites and probes. The sensor exhibits an ultra-high sensitivity of approximately 6.67 × 1019 nm/M, and the LOD is obtained as low as 5.36 × 10-20 M which is several orders of magnitude lower compared to other conventional methods. It is also experimentally demonstrated that the sensor possesses excellent specificity, stability, and repeatability, which may be adapted for detecting real clinical samples.

SIGNIFICANCE

The CQDs-functionalized optical fiber SPR sensor exhibits substantial potential for precisely detecting Co2+ of trace amounts, which is especially vital for scarce clinical samples. Additionally, the sensing platform with sample sensor fabrication and measurement configuration introduces a novel, highly sensitive approach to biochemical analysis, particularly adapting for applications involving the detection of trace targets, which could also be employed to detect various biochemical targets by facile modification of CQDs with specific groups or biomolecules.

Research progress of fluorescent composites based on cyclodextrins: Preparation strategies, fluorescence properties and applications in sensing and bioimaging

Fluorescence analysis has been regarded as one of the commonly used analytical methods because of its advantages of simple operation, fast response, low cost and high sensitivity. So far, various fluorescent probes, with noble metal nanoclusters, quantum dots, organic dyes and metal organic frameworks as representatives, have been widely reported. However, single fluorescent probe often suffers from some deficiencies, such as low quantum yield, poor chemical stability, low water solubility and toxicity. To overcome these disadvantages, the introduction of cyclodextrins into fluorescent probes has become a fascinating approach. This review (with 218 references) systematically covers the research progress of fluorescent composites based on cyclodextrins in recent years. Preparation strategies, fluorescence properties, response mechanisms and applications in sensing (ions, organic pollutants, bio-related molecules, temperature, pH) and bioimaging of fluorescent composites based on cyclodextrins are summarized in detail. Finally, the current challenges and future perspectives of these composites in relative research fields are discussed.

Eco-friendly optical sensor for precise detection of gold ions in diverse matrices through the integration of β-2-hydroxybenzyl-3-methoxy-2-hydroxyazastyrene in a PVC membrane

An environmentally conscious methodology is investigated for the precise and discerning identification of trace concentrations of gold ions in diverse matrices. A novel optical sensor membrane is proposed for the determination of Au3+ ions, utilizing the immobilization of β-2-hydroxybenzyl-3-methoxy-2-hydroxyazastyrene (HMHS) entrapped in polyvinyl chloride (PVC). The sensor incorporates sodium tetraphenylborate (Na-TPB) as the ionic additive and dibutyl phthalate (DBP) as a plasticizer. Under optimal conditions, the suggested sensor exhibits a linear calibration response to Au3+ ions within a concentration range of 5.0 to 165 ng mL-1. Detection and quantification limits are specified as 1.5 and 4.8 ng mL-1, respectively, with a rapid response time of 5.0 min. Upon presentation, this optical sensor not only affirms high reproducibility, stability, and an extended operational lifespan but also showcases exceptional selectivity for Au3+ ions. Notably, no discernible interference is observed when assessing the potential influence of other cations and anions on Au3+ ion detection. The adaptability of this optical sensor is validated through its successful application in determining Au3+ ion concentrations across various sample types, including water, environmental, cosmetics, and soil matrices.

The highly selective green colorimetric detection of yttrium ions in biological and environmental samples using the synergistic effect in an optical sensor

A new eco-friendly method for creating an optical sensor membrane specifically designed to detect yttrium ions (Y3+) has been developed. The proposed sensor membrane is fabricated by integrating 4-(2-arsonophenylazo) salicylic acid (APASA), sodium tetraphenylborate (Na-TPB), and tri-n-octyl phosphine oxide (TOPO) into a plasticized poly(vinyl chloride) matrix with dimethyl sebacate (DMS) as the plasticizer. In this sensor membrane, APASA functions dually as an ionophore and a chromoionophore, while TOPO enhances the complexation of Y3+ ions with APASA. The composition of the sensor membrane has been meticulously optimized to achieve peak performance. The current membrane exhibits a linear dynamic range for Y3+ ions from 8.0 × 10-9 to 2.3 × 10-5 M, with detection and quantification limits of 2.3 × 10-9 and 7.7 × 10-9 M, respectively. No interference from other potentially interfering cations and anions was observed in the determination of Y3+. The membrane showed strong stability and a swift response time of about 3.0 minutes, with no signs of APASA leaching. This sensor is highly selective for Y3+ ions and can be renewed by treating it with 0.15 M HNO3. It has been effectively applied to measure Y3+ in nickel-based alloys, as well as in biological and environmental samples.

Nanomaterials Based on 2,7,12,17-Tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine Exhibiting Bifunctional Sensitivity for Monitoring Chloramphenicol and Co2

Monitoring antibiotic retention in human body fluids after treatment and controlling heavy metal content in water are important requirements for a healthy society. Therefore, the approach proposed in this study is based on developing new optical sensors using porphyrin or its bifunctional hybrid materials made with AuNPs to accomplish the accurate detection of chloramphenicol and cobalt. To produce the new optical chloramphenicol sensors, 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine (TBAP) was used, both alone in an acid medium and as a hybrid material with AuNPs in a water-DMSO acidified environment. The same hybrid material in the unchanged water-DMSO medium was the sensing material used for Co2+ monitoring. The best results of the hybrid materials were explained by the synergistic effects between the TBAP azaporphyrin and AuNPs. Chloramphenicol was accurately detected in the range of concentrations between 3.58 × 10-6 M and 3.37 × 10-5 M, and the same hybrid material quantified Co2+ in the concentration range of 8.92 × 10-5 M-1.77 × 10-4 M. In addition, we proved that AuNPs can be used for the detection of azaporphyrin (from 2.66 × 10-5 M to 3.29 × 10-4 M), making them a useful tool to monitor porphyrin retention after cancer imaging procedures or in porphyria disease. In conclusion, we harnessed the multifunctionality of this azaporphyrin and of its newly obtained AuNP plasmonic hybrids to detect chloramphenicol and Co2+ quickly, simply, and with high precision.

Dual-emission ciprofloxacin-gold nanoclusters enable ratiometric sensing of Cu2+, Al3+, and Hg2

An innovative triple optical sensor is presented that utilizes gold nanoclusters (GNCs) stabilized with ciprofloxacin (CIP) and bovine serum albumin (BSA). The sensor is designed to identify three critical metal ions, namely Cu2+, Al3+, and Hg2+. Under 360 nm excitation, the synthesized CIP-BSA-GNCs demonstrate dual fluorescence emission with peaks at 448 nm (blue) and 612 nm (red). The red emission is associated with the interior of the CIP-BSA-GNCs, whereas the blue emission results from the surface-bound CIP molecules. The sensitive and selective fluorescent nanosensor CIP-BSA-GNCs were employed to detect Cu2+, Al3+, and Hg2+ ions. Cu2+ effectively quenched the fluorescence intensity of the CIP-BSA-GNCs at both peaks via the internal charge transfer mechanism (ICT). Cu2+ could be detected within the concentration range 1.13 × 10-3 to 0.05 µM, with a detection limit of 0.34 nM. Al3+ increased the intensity of CIP fluorescence at 448 nm via the chelation-induced fluorescence enhancement mechanism. The fluorescence intensity of the core CIP-BSA-GNCs at 612 nm was utilized as a reference signal. Thus, the ratiometric detection of Al3+ succeeded with a limit of detection of 0.21 nM within the dynamic range 0.69 × 10-3 to 0.07 µM. Hg2+ effectively quenched the fluorescence intensity of the CIP-BSA-GNCs at 612 nm via the metallophilic interaction mechanism. The fluorescence intensity of CIP molecules at 448 nm was utilized as a reference signal. This allowed for the ratiometric detection of Hg2+ with a detection limit of 0.7 nM within the concentration range 2.3 × 10-3 to 0.1 µM.

Utilization of a novel PVC- optical sensor for high sensitive and selective determination of zinc ion in real samples

A novel and highly specific bulk membrane optode was developed for the ultra-sensitive detection of zinc(II) in biological, pharmaceutical, and water samples. The polymer inclusion membrane (PIM) utilized in this study consists of 50% polyvinyl chloride (PVC) as a base polymer, 9.00% DOP (dioctylphthalate) as the plasticizer, and 40.0% D2EHPA (di(2-ethlyhexyl)phosphoric acid) as the carrier. To facilitate the spectrophotometric determination of zinc(II), a colorimetric reagent, namely 4-(2-arsonophenylazo) salicylic acid (APASA) {1.00%, m/v}, was employed. When Zn(II) was extracted into the PIM, it led to the creation of the zinc-D2EHPA complex. This complex then underwent a reaction with APASA, resulting in the formation of a red Zn - APASA complex with a maximum absorption wavelength (λmax) of 558 nm. To optimize the response of the optode, a central composite design was employed, considering variables such as the amount of additive and reagent, response time, and pH. When operated under the specific optimal conditions, the sensor demonstrated a limit of quantification (LOQ) of 0.74 ng/mL (equivalent to 1.17 × 10-8 M) and a limit of detection (LOD) of 0.22 ng/mL (equivalent to 3.44 × 10-9 M). The optode membrane demonstrated excellent reproducibility, stability, and a relatively long lifespan, making it suitable for precise and accurate monitoring of Zn(II) ion content. Regeneration of the optode was achieved effectively using 0.25 nitric acid solution, and its response exhibited reversibility and reproducibility, showed a relative standard deviation of less than 1.33%. Moreover, the PIM-APASA optode exhibited a high level of effectiveness in accurately determining the presence of Zn(II) ions in real environmental samples.

An innovative approach in titanium determination based on incorporating 2-amino-4-((4-nitrophenyl)diazenyl)pyridine-3-ol in a PVC membrane

A pioneering optical sensor has been effectively developed to achieve precise and reliable detection of titanium ions. The sensor employs an optode membrane composed of 2-amino-4-((4-nitrophenyl)diazenyl)pyridine-3-ol (ANPDP) and sodium tetraphenylborate (NaTPB) incorporated into a plasticized PVC matrix, with dioctyl sebacate (DOS) acting as the plasticizer. When exposed to Ti4+ ions at pH 8.25, the color of the sensing membrane undergoes a distinctive transformation from yellow-orange to violet. Extensive investigations were carried out to assess and optimize various factors influencing the efficiency of ion uptake. Through careful experimentation, the optimum conditions were determined to be 60.0% DOS, 6.0% ANPDP, 30% PVC, and 4.0% NaTPB, with a rapid response time of 5.0 min. Within these conditions, the developed optode demonstrates an impressive linear range of 3.0-225 ng mL-1, boasting detection (LOD) and quantification (LOQ) limits of 0.91 and 2.95 ng mL-1, respectively. Moreover, the precision of the sensor, as indicated by the relative standard deviation (RSD%), remained consistently below 1.55% in six replicate determinations of 100 ng mL-1 Ti4+ across diverse membranes. The selectivity of the sensor was rigorously examined for a range of cations and anions, successfully establishing the tolerance limits for interfering species. Notably, the presence of EDTA as a masking agent did not compromise the high selectivity of the sensor. Consequently, the innovative probe holds significant potential as a reliable analytical tool for quantifying titanium content in various samples, including water, geological materials, soil, plants, paints, cosmetics, and plastics.

A modified selective optical sensor for selenium determination based on incorporating xylenol orange in a poly(vinyl chloride) membrane

A novel optical sensor has been developed to measure selenium ions. The sensor membrane was created by mixing xylenol orange (XO) and sodium tetraphenylborate (NaTPB) with a plasticized poly(vinyl chloride) membrane that contained o-nitrophenyl octyl ether (o-NPOE) as a plasticizer. XO was previously established for use in a colorimeter to measure selenium in water and other media. At pH 6.6, the color of the detecting membrane changed from orange to pink when in contact with Se4+ ions. Various variables affecting the uptake efficiency were evaluated and optimized. Under optimum conditions (i.e., 30% PVC, 60% o-NPOE, and 5.0% of both XO and NaTPB for 5.0 min as the response time), the proposed sensor displayed a linear range 10-175 ng mL-1 with the detection and quantification limits of 3.0 and 10 ng mL-1, respectively. Also, the precision (RSD%) was better than 2.2% for six replicate determinations of 100 ng mL-1 Se4+ in various membranes. For the detection of Se4+, the selectivity of the sensor membrane was investigated for a number of possible interfering inorganic cations, but no appreciable interference was found. With the use of a 0.3 M HCl solution, the sensor was successfully restored, and the response that may have been reversible and reproducible exhibited an RSD% of less than 2.0%. The sensor has been successfully used to analyze Se4+ ions in environmental and biological materials.

Optical chemical sensor of Gd(iii) based on 5-(2'-bromophenyl- azo)-6-hydroxypyrimidine-2,4-dione immobilized on poly(methyl methacrylate) and 2-nitrophenyloctylether matrix

A novel optical chemical sensor (optode) was fabricated for the determination of Gadolinium ions. The optical sensor was prepared by incorporating a recently synthesized ionophore, 5-(2'-bromophenylazo)-6-hydroxy pyrimidine-2,4-dione (BPAHPD), and 2-nitrophenyloctylether (NPOE) as a plasticizer in poly(methyl methacrylate) (PMMA) membrane. The color of the sensing membrane in contact with Gd(iii) ions changed from yellow to red-orange due to the adsorption of Gd(iii) with the maximum absorbance (λ max) at 563 nm. The chemical sensor responds optimally towards Gd(iii) ions at the optimum conditions of pH 7.5, contact time 10 min, 150 ng mL-1 Gd(iii), and 5.0 mL solution. The linear regression equation achieved was A = 4.36C (μg mL-1) - 0.15 (r = 0.9976). A linear Gd(iii) calibration curve can be established in the concentration range of 5.0-250 ng mL-1 with R 2 = 0.9976. Detection and quantification limits are 1.47 and 4.75 ng mL-1, respectively. The molar absorptivity and Sandell sensitivity are found to be 6.86 × 107 L mol-1 cm-1 and 0.023 ng cm-2, respectively. In addition to its stability and reproducibility, the optode revealed a great selectivity toward Gd(iii) ions as compared to other coexisting ions in real samples. The recovery of Gd(iii) ions from the sensor material was achieved using 0.4 M HNO3 . The offered optode sensor membrane has been employed to monitor Gd(iii) in soil, sediments, river water, and urine with an internal standard addition method and compared statistically with the ICP-OES method. The results revealed calculated t-values between 1.11-1.85, whereas F values were in the range of 2.46-3.77 which did not exceed the theoretical values, indicating no significant difference at 95% confidence level. The observed percent recovery is in the range of 97.24-102.52%.

A novel sensor for the selective monitoring of trace ytterbium ions using an agarose-based optical membrane

A novel highly selective sensitive optical sensor was prepared via the chemical immobilization of β-2-hydroxybenzyl-5-bromo-2-hydroxyazastyrene (HBBHAS) on an epoxy-activated agarose membrane pieces. The absorbance variation of the immobilized azastyrene film on agarose upon the addition of 1.5 × 10⁻⁵ M aqueous solutions of La³⁺, Y³⁺, Al³⁺, Sc³⁺, Sm³⁺, Eu³⁺, Lu³⁺, Fe³⁺, Ce³⁺, Cr³⁺, S₂O₃²⁻, Tb³⁺, Mn²⁺ and KIO₃ revealed substantially higher changes for the Yb³⁺ ion compared to the other considered ions. Thus, using HBBHAS as an appropriate ionophore, a selective optical sensor for Yb³⁺ was prepared via its chemical immobilization on a transparent agarose membrane. The effects of pH, reagent concentration, and time duration of the reaction of immobilizing the reagent were examined. A distinct change in the maximum absorbance of the reagent was established on contact of the sensing membrane with Yb³⁺ ions at pH = 4.25. For the membrane sensor, a linear relationship was observed between the variation in membrane absorbance (ΔA) at 424 nm and Yb³⁺ concentrations in the range of 4.75 × 10⁻⁵ to 6.20 × 10⁻¹⁰ M with a detection limit of 1.9 × 10⁻¹⁰ M for Yb³⁺. The effects of some potentially interfering ions on the assessment of Yb³⁺ were analyzed, and no substantial interference was found. The sensor showed a short response time and decent durability with no reagent leaching. The recovery of Yb³⁺ ions from the sensor material was performed using 0.3 M HNO₃ and its response was reversible and reproducible with RSD ≥ 1.95%. This study reports a non-toxic, economical, stable, accurate, easy-to-use, and novel optical sensor material to assess Yb³⁺ in synthetic and environmental water samples.

The immobilized optical sensor preparation and its measurement procedure.