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Fluorescence emission spectra (excitation wavelength = 365 nm) of the hydrolysate of Cs4PbBr6 NCs (66 mg L⁻¹ in n-hexane) at different amount of water added after vigorous shaking for 2 min then keeping undisturbed under ambient temperature for 1 h for better separation of the aqueous microspheres and n-hexane. Insert: calibration curve for water determination (emission wavelength = 517 nm). The error bars show the standard deviation of three parallel determinations
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A smartphone-based ratiometric fluorescence device was designed to monitor the reaction kinetic process under vigorous mixing conditions, demonstrated by the hydrolysis of Cs4PbBr6 nanocrystals (NCs). In the presence of trace water, part of Cs4PbBr6 NCs (non-fluorescent) was converted to CsPbBr3 NCs (strong fluorescent). Using anthracene as the ref...
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High‐quality perovskite films are essential for achieving high performance of optoelectronic devices; However, solution‐processed perovskite films are known to suffer from compositional and structural inhomogeneity due to lack of systematic control over the kinetics during the formation. Here, the microscopic homogeneity of perovskite films is succ...
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... On the other hand, the advent of universal digital imaging technology offers new possibilities for simple colorimetric detection. With the help of digital imaging technology, a colorimetric sensor becomes more real, simple, efficient, and sensitive in quantification [24]. At present, the use of portable devices such as SMARTPHONE for real-time monitoring has become an area of great interest [24][25][26][27][28][29][30][31][32][33][34][35]. ...
... With the help of digital imaging technology, a colorimetric sensor becomes more real, simple, efficient, and sensitive in quantification [24]. At present, the use of portable devices such as SMARTPHONE for real-time monitoring has become an area of great interest [24][25][26][27][28][29][30][31][32][33][34][35]. A proper synergy between the smartphone and the sensor is very important because the sensor will collect the data and then the mobile phone software can process the data and generate readable information [28][29][30]. ...
... In addition, other color spaces are also used, such as the following: cyan, magenta, yellow, and key (black) (CMYK) as well as hue, saturation, and value (HSV) [32]. Almost all optical analyses can be integrated with smart platforms, including absorbance, fluorescence [24,27,31], reflectivity [25], surface plasmon resonance (SPR) [27], and bioluminescence [30]. Detection methods based on RGB analysis using SMARTPHONE-like smart platforms do not require expensive instruments, making on-site detection and remote transmission and analysis of the results possible. ...
This paper reports the successful development and application of an efficient method for quantifying Pb2+ in aqueous samples using a smartphone-based colorimetric device with an imprinted polymer (IIP). The IIP was synthesized by modifying the previous study; using rhodizonate, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N,N′-methylenebisacrylamide (MBA), and potassium persulfate (KPS). The polymers were then characterized. An absorption study was performed to determine the optimal conditions for the smartphone-based colorimetric device processing. The device consists of a black box (10 × 10 × 10 cm), which was designed to ensure repeatability of the image acquisition. The methodology involved the use of a smartphone camera to capture images of IIP previously exposed at Pb2+ solutions with various concentrations, and color channel values were calculated (RGB, YMK HSVI). PLS multivariate regression was performed, and the optimum working range (0–10 mg L−1) was determined using seven principal components with a detection limit (LOD) of 0.215 mg L−1 and R2 = 0.998. The applicability of a colorimetric sensor in real samples showed a coefficient of variation (% RSD) of less than 9%, and inductively coupled plasma mass spectrometry (ICP-MS) was applied as the reference method. These results confirmed that the quantitation smartphone-based colorimetric sensor is a suitable analytical tool for reliable on-site Pb2+ monitoring.
... On the one hand, the rate of ion diffusion depended on temperature, which was one of the key factors for kinetics-tunable fluorescence. On the other hand, as the concentration of CsBr (escaped from the SiO 2 shell) gradually increased, the common-ion effect 58 of CsBr became dominant, making the PL quenching rate slower with prolonged reaction time. We speculated that the dissolved CsBr reduced the concentration gradient of Cs + inside and outside the SiO 2 shell, thereby decreasing the diffusion rate of Cs + decomposed from internal CsPbBr 3 , 59 and the same effect exists in CsI, as well. ...
The spoilage and forgery of perishable products such as food, drugs, and vaccines cause serious health hazards and economic loss every year. Developing highly efficient and convenient time-temperature indicators (TTIs) to realize quality monitoring and anticounterfeiting simultaneously is urgent but remains a challenge. To this end, a kind of colorimetric fluorescent TTI, based on CsPbBr3@SiO2 nanoparticles with tunable quenching kinetics, is developed. The kinetics rate of the CsPbBr3-based TTIs is easily regulated by adjusting temperature, concentration of the nanoparticles, and addition of salts, stemming from the cation exchange effect, common-ion effect, and structural damage by water. Typically, when combined with europium complexes, the developed TTIs show an irreversible dynamic change in fluorescent colors from green to red upon increasing temperature and time. Furthermore, a locking encryption system with multiple logics is also realized by combining TTIs with different kinetics. The correct information only appears at specific ranges of time and temperature under UV light and is irreversibly self-erased afterward. The simple and low-cost composition and the ingenious design of kinetics-tunable fluorescence in this work stimulate more insights and inspiration toward intelligent TTIs, especially for high-security anticounterfeiting and quality monitoring, which is really conducive to ensuring food and medicine safety.
A fast and efficient method was developed for obtaining europium(III)-doped surface-modified carbon dots with a
hydrophobic coating. This surface functionalization improved the dispersibility of the nanoparticles in non-polar media, as
well as modified the accessibility of water molecules to the europium ions. These two features allowed studying the application
of doped carbon dots as moisture nanochemosensor, demonstrating high stability over time of both the photoluminescent
signal intensity and the stability of the dispersions. The developed nanochemosensor was used to determine water in toluene
with a detection limit of 8.5 × 10 −4 M and a quantification limit of 2.4 × 10 −3 M. The proposed system matches and even
improves other methodologies for water determination in organic solvents; it has a low detection limit and a fast response
time (almost instantaneous) and requires neither expensive material nor trained personnel. The results suggest a promising
future for the development of a new sensing phase for moisture determination in lubricant base oil.
A luminescent hydroxyl-functionalized MIL-53(Al) (OH-MIL-53(Al)) was prepared by one-step solvent thermal method for multiresponsive fluorescence sensor. The OH-MIL-53(Al) exhibited uniform nanospheres with average diameter of 150±20 nm, flexible three-dimensional frameworks, and good dispersion in water. The OH-MIL-53(Al) emitted green fluorescence with a maximum wavelength of 515 nm which showed good fluorescence quenching response for sensing F⁻ and fluoresce fluorescence enhancement response for water, with good day-to-day stability. The mechanism was based on protonation/deprotonation of hydroxyl group located on OH-MIL-53(Al). Good linear relationship could be found between the luminescence intensity of 515 nm and F⁻ concentrations in the range of 0-60 μM with a determination limit of 70 nM. At the concentrations from 0% to 100%, the fitting curve for water content was in good agreement with the linear equation, and the detection limit was 0.10%. OH-MIL-53(Al) demonstrated excellent fluorescence sensing performance, indicating that it could be used as a multiresponsive sensor to practical application.
Detection of trace quantities of water in laboratory and industrial processes is very crucial. Monitoring humidity is of vital importance in maintaining ambient atmosphere in places like hospitals, in climate sciences, automated devices, intelligent systems, etc. Development of optical detection systems for water and humidity entails real time progress in industrial processing and storage, human–machine interactions, clinical diagnosis and security solutions and many more. This review provides a comprehensive study of developments made in the field of optical sensing of water and humidity in the last decade. The compilation has been segmented into various sub-sections based on various molecular scaffolds. It covers a library of structural motifs containing anthracene, rhodamine, coumarin, bodipy, pyrene, naphthalene, naphthalimide, anthraquinone, tetraphenylethene, triphenylamine, thioxanthone, triarylmethane, etc. These have followed versatile mechanistic pathways like intramolecular charge transfer, photo-induced electron transfer, aggregation induced emission, solvatochromism, forster resonance energy transfer, hydrogen bonding interactions, reaction- based formation or cleavage of bonds, etc. to respond to presence of water in organic solvents or atmosphere by colorimetry or fluorimetry. All the reported probes have been dealt in a case by case manner with respect to their working mechanisms, advantages, limitations and applications. The detection limit and quantification limit values have been assembled to compare the efficacies of different probes. Real life applications of the sensors have been demonstrated, which shows that the scope of employing chemosensors in solving various real-time problems is huge and bright. It outlays concretely the opportunities and scope for future works.
In organic solvents, water is the most frequently found impurity. It interferes with many reactions, so it can be a reason for importance of its determination. Karl Fischer titration is a commonly used method for this purpose. However, some disadvantages particularly the inability of continuous analysis limit its applications. The current study reviews the optical sensors/nanosensors developed for the determination of water and demonstrates their applications in checking water impurity in organic solvents. Such optical sensors are highly demanded in the sensing procedures due to their simplicity and low price. Almost these methods do not need any expensive or complicated vehicles. This review focuses on optical sensors/nanosensors for the quantification of water content in organic solvents from 2016 to 2020 and is an update of Jung et al. work in 2016. The reported sensors/nanosensors are categorized into two types: spectrophotometry and spectrofluorimetry; each of them is classified based on the used materials for water sensing. The details of each reported method are explained in this review in detail, and their analytical characteristics are given as a table.
Total volatile basic nitrogen (TVB-N) content is the most widely used index for the assessment of fish freshness. Herein, a smartphone-integrated colorimetric sensor of TVB-N is developed based on a functional hydrogel loaded with [email protected]2 core-shell nanocomposites and β-d-glucose pentaacetate (β-d-GP). In the sensing hydrogel, [email protected]2 serves as a colorimetric substance and β-d-GP is a precursor of reducing agent. TVB-N can permeate the sensing hydrogel, causing an alkaline environment in which β-d-GP is hydrolyzed to produce β-d-glucose. A redox reaction between MnO2 and β-d-glucose can occur and thus the TVB-N can induce the etching of MnO2 layer of the [email protected]2. Owing to the change of localized surface plasma resonance (LSPR) effect, the color of AuNPs changing from purple to red is easily distinguished by the naked eye. To quantify the variation conveniently, the color information is digitized by a smartphone combined with RGB analysis. The hydrogel sensing platform is further used for real-time monitoring of fish spoilage successfully. The introduction of smartphone avoids the usage of expensive instrument and opens a practical way for cost-effective, non-invasive, and portable monitoring of foodstuff freshness.
