CuInGaSe nanocrystals for detection of trace amount of water in D2O (at ppm level)

A dynamic Eu(III)-macrocycle served as the turn-on fluorescent probe for distinguishing H2O from D2O

H2O and D2O are an important pair of analogues, and their high-efficient detections are closely related to fields of chemical industry, food processing, semiconductor, environmental monitoring, etc. Because of their extremely similar physical and chemical properties, H2O and D2O can be mutually soluble in any ratios, and it is generally thought that the discrimination of H2O and D2O is an enormous challenge. Herein, upon the fact that vibrational frequency of O-H is greater than O-D, we design a dynamic Eu(III)-macrocycle Eu-2a with two emitters which exhibits the imine bond breakage of macrocycle emitter H2L2a in H2O or D2O, resulting in the turn-on fluorescence of Eu(III) emitter. For their differential fluorescence sensing signals of Eu-2a on three emission bands (433, 500 and 615 nm), the statistical analysis method is employed to produce fully separated fingerprints and thus high-throughput discrimination of 13 common solvents, especially the H2O and D2O. Fluorescent titration experiments by instrumental or smartphone-based analysis method also prove the successful determination of proportional H2O/D2O mixtures together with the good sensitivity and wide linear response range. Moreover, this H2O-triggered fluorescent complex Eu-2a used as the fluorescence ink also shows its potential in information encryption application. This article must be a valuable reference for the areas of lanthanide-based luminescent material, multianalyte detection and information encryption.

Simple Self-Powered Sensor for the Detection of D2O and Other Isotopologues of Liquid Water

Distinguishing between heavy water and regular water has been a continuing challenge since these isotopologues of water have very similar physical and chemical properties. We report the development and evaluation of a simple, inexpensive sensor capable of detecting liquid D2O and other isotopologues of liquid water through the measurement of electrical signals generated from a nanoporous alumina film. This electrical output, consisting of a sharp voltage pulse followed by a separate broad voltage pulse, is present during the application of microliter volumes of liquid. The amplitude and temporal characteristics of these pulses have been combined to enable four diagnostic parameters for sensing D2O and H218O. The sensing mechanism is based on different modification effects on the alumina surface by H2O and D2O, spatially localized variations in the surface potential of alumina induced by isotopically substituted water molecules, combined with the effect of isotopic composition on charge transfer. As a proof-of-concept demonstration, a sensing system has been developed that provides real-time detection of liquid D2O in a stand-alone system.

Role of Noncovalent Interactions in N,P-Functionalized Luminescent Carbon Dots for Ultrasensitive Detection of Moisture in D2O: Boosting Visible-NIR Light Sensitivity

It is highly desirable to design cost-efficient and eco-friendly fluorometric sensors that can efficiently detect water contamination in D₂O and other expensive organic solvents. Herein, we have synthesized N,P-codoped carbon dots (N,P-CDs) from o-phenylene diamine (o-PDA) and H₃PO₄ through the bottom-up carbonization method. Heteroatom co-doping increases the absorption cross section in the visible-NIR range, followed by the formation of stable emissive states in longer-wavelength regions. We have critically investigated the noncovalent interactions (especially H-bonding interactions) of various surface functional groups with surrounding solvent media through a detailed structure-property correlation. Based on the sensitivity of noncovalent H-bonding interactions to the stability of longer-wavelength emissive domains, we have utilized these N,P-CDs as cost-effective fluorometric sensors of water/moisture contamination in D₂O especially under visible-NIR light; the optical sensitivity reaches up to 0.1 volume (%) level. The detailed sensing mechanism has been further supported by a computational study through a simple visualization approach by mapping and analyzing all possible noncovalent interactions between the CDs and the solvent medium.

1O2-Relevant Afterglow Luminescence of Chlorin Nanoparticles for Discriminative Detection and Isotopic Analysis of H2O and D2O

Discriminative detection between D₂O and H₂O is important for diverse fields but challenging due to their high similarity in chemical and physical properties. Current molecular sensors for D₂O detection generally rely on the spectral change of fluorophores with suitable pK_a in response to D₂O and H₂O with slightly different pH acidity. Herein, we report a new and facile D₂O sensor by using singlet oxygen (¹O₂)-relevant afterglow luminescence of chlorin e4 nanoparticles (Ce4-NPs) to achieve distinguishable detection between D₂O and H₂O. As ¹O₂ is a key initiator involved in the afterglow luminescence process, it displays a 22-fold longer lifetime in D₂O relative to H₂O and thereafter generates more dioxetane intermediates after laser irradiation to lead to ultimate afterglow brightness of Ce4-NPs in D₂O. In addition, Ce4-NPs are capable of quantitatively detecting the amount of H₂O in D₂O with a limit of detection (LOD) of 1.45%. Together, this study broadens the utility of afterglow materials and presents a facile strategy for isotopic purity analysis of heavy water.

Modulating Dual Fluorescence Emissions in Imine-Based Probes to Distinguish D2O and H2O

How to distinguish D₂O and H₂O and determine the trace H₂O content in D₂O solvent, by using molecule-based spectral probes, is an intriguing topic in analytical chemistry, yet considerably few examples remain up to now, likely due to the very similar physical/chemical properties between D₂O and H₂O. In this work, we found that both the hydrolysis reactions to release fluorescent amines and aggregation-induced emission (AIE) of imines, functioning as dual fluorescence signals to distinguish D₂O and H₂O, could be modulated by changing the imine structures. The hydrophobicity of imines showed an important contribution to the ability of modulating the hydrolysis reactions and AIE, demonstrating a significant difference on fluorescence signals in D₂O and H₂O solvents. Among all tested imines, probe 3, condensed from 2-naphthylamine and salicylaldehyde, was found to have the potential ability to act as an ideal candidate for probing the H₂O content in D₂O solvent, particularly in a low H₂O content range, using the ratiomeric emission signals.

Ratiometric fluorescent and colorimetric dual-modal sensing strategy for discrimination and detection of D2O from H2O

A ratiometric fluorescent and colorimetric dual-modal sensing strategy is reported to distinguish and detect D₂O from H₂O based on ground-state proton transfer for the first time. It enables synchronous dual-modal changes towards different fractions of D₂O and facilitates naked-eye recognition. The probe can provide a more accurate monitoring protocol for D₂O analysis.

A water-soluble sensor for distinguishing D2O from H2O by dual-channel absorption/fluorescence ratiometry

A novel D2O optical sensor Cy with integrated great water-solubility, absorption/fluorescence dual-channel ratiometric response and even red-green-blue visual sensing application.

Analysis of the Isotopic Purity of D2O with the Characteristic NIR-II Phosphorescence of Singlet Oxygen from a Photostable Polythiophene Photosensitizer

D₂O plays important roles in a variety of fields (such as the nuclear industry and bioorganic analysis), and thus its isotopic purity (H₂O contents) is highly concerned. Due to its highly similar physical properties to H₂O and large excess amounts of H₂O over D₂O, it is challenging to distinguish D₂O from H₂O. On the basis of the characteristic NIR-II phosphorescence of singlet oxygen (¹O₂), and the fact that H₂O is a more efficient quencher for ¹O₂ than D₂O, here, we proposed to simply use the 1275 nm emission of ¹O₂ for the analysis of the isotopic purity of D₂O. In normal cases (a xenon lamp for excitation), such steady-state emission is extremely weak for valid analytical applications, we thus employed laser excitation for intensification. To this goal, a series of photosensitizers were screened, and eventually polythiophene PT10 was selected with high singlet oxygen quantum yield (Φ_Δ = 0.51), high H₂O/D₂O contrast, and excellent photostability. Upon excitation with a 445 nm laser, a limit of detection (LOD, 3σ) of 0.1% for H₂O in D₂O was achieved. The accuracy of the proposed method was verified by the analysis of the isotopic purity of several D₂O samples (with randomly added H₂O). More interestingly, the hygroscopicity of D₂O was sensitively monitored with the proposed probe in a real-time manner; the results of which are important for strengthening the care of D₂O storage and the importance of humidity control during related investigations. Besides D₂O isotopic purity evaluation, this work also indicated the potential usefulness of the NIR-II emission of singlet oxygen in future analytical detection.

Green preparation of carbon dots with different surface states simultaneously at room temperature and their sensing applications

It is a considerable challenge to develop environmental friendly, low-cost methodology for green preparation of carbon dots (CDs). Herein, CDs with different surface states are prepared using o-phenylenediamine (o-PD) and hydroquinone (HQ) as precursors via oxidation/polymerization and Schiff base reaction at room temperature without additional oxidizing agents. Two CDs products (YCDs and GCDs) are obtained after separation with silica gel column chromatography based on their polarity differences. The different surface states endow these two CDs with different properties. The rich NO₂ and OH groups on the surface of YCDs contribute to a narrow band gap, resulting in the red-shifted photoluminescence (PL) emission of this CDs product, making it a sensitive probe for the detection of toxic pollutant p-nitrophenol (p-NP) attributed to the inner filter effect, along with a detection limit of 0.08 μmol/L. GCDs are characterized with abundant surficial NH₂ groups, and can be used as a potential probe to detect H₂O content in D₂O, giving a detection limit of 0.17 vol%.

Discussions of Fluorescence in Selenium Chemistry: Recently Reported Probes, Particles, and a Clearer Biological Knowledge

In this review from literature appearing over about the past 5 years, we focus on selected selenide reports and related chemistry; we aimed for a digestible, relevant, review intended to be usefully interconnected within the realm of fluorescence and selenium chemistry. Tellurium is mentioned where relevant. Topics include selenium in physics and surfaces, nanoscience, sensing and fluorescence, quantum dots and nanoparticles, Au and oxide nanoparticles quantum dot based, coatings and catalyst poisons, thin film, and aspects of solar energy conversion. Chemosensing is covered, whether small molecule or nanoparticle based, relating to metal ion analytes, H2S, as well as analyte sulfane (biothiols-including glutathione). We cover recent reports of probing and fluorescence when they deal with redox biology aspects. Selenium in therapeutics, medicinal chemistry and skeleton cores is covered. Selenium serves as a constituent for some small molecule sensors and probes. Typically, the selenium is part of the reactive, or active site of the probe; in other cases, it is featured as the analyte, either as a reduced or oxidized form of selenium. Free radicals and ROS are also mentioned; aggregation strategies are treated in some places. Also, the relationship between reduced selenium and oxidized selenium is developed.

A dual-site controlled fluorescent sensor for the facile and fast detection of H2O in D2O by two turn-on emission signals

A dual-site controlled fluorescent sensor based on FRET mechanism was constructed for the facile and fast detection of H₂O content in D₂O.

Fe3+-Catalyzed low-temperature preparation of multicolor carbon polymer dots with the capability of distinguishing D2O from H2O

Carbon polymer dots (CPDs) exhibit differential optical responses to H₂O and D₂O due to the different surface states of CPDs.

Nanomaterials for luminescent detection of water and humidity

Significant advances of typical nanomaterials in the luminescent detection of water and humidity are presented.

Bandgap Tunable AgInS based Quantum Dots for High Contrast Cell Imaging with Enhanced Photodynamic and Antifungal Applications

Herein, we report a facile microwave-assisted synthesis of cadmium-free water-soluble silver indium sulfide (AgInS2 or AIS) and AgInS@ZnS (or AIS@ZnS) core-shell quantum dots (QDs) using glutathione (GSH) as stabilizer. The core and core-shell nanocrystals exhibit tunable bandgap ranging of 2.3-3.1 and 2.4-3.5 eV, mean particle size of 2.5 and 3.25 nm, quantum yield of 26% and 49%, and fluorescence lifetimes of 326 and 438 ns, respectively. The core-shell QDs exhibit color-tunable emission in the visible region (500 to 600 nm), where the tunability was achieved by varying the molar ratio of Ag:In in the precursors. In vitro evaluation of antifungal activity of these water/ buffer stable QDs against the fungal pathogen, Candida albicans demonstrated that these were not toxic to the fungal cells upto a concentration of 100 µg/ml for 16 hours of incubation. Confocal imaging and spectrofluorometric studies showed enhanced fluorescence inside the microbial cells suggesting that AIS@ZnS particles had the capability to easily penetrate the cells. The increased generation of reactive oxygen species was evaluated for the core-shell QDs (photosensitizers) by using 9, 10-anthracenediyl-bis(methylene)dimalonic acid (ABMDMA) as singlet oxygen (1O2) scavenger molecule. These QDs have the potential for use as high contrast cell imaging, photodynamic and antifungal agents.

Eco-friendly synthesis of CuInS2 and CuInS2@ZnS quantum dots and their effect on enzyme activity of lysozyme

We report on the green and facile aqueous microwave synthesis of glutathione (GSH) stabilized luminescent CuInS₂ (CIS, size = 2.9 nm) and CuInS₂@ZnS core–shell (CIS@ZnS, size = 3.5 nm) quantum dots (QDs). The core–shell nanostructures exhibited excellent photo- and water/buffer stability, a long photoluminescence (PL) lifetime (463 ns) and high PL quantum yield (PLQY = 26%). We have evaluated the comparative enzyme kinetics of these hydrophilic QDs by interacting them with the model enzyme lysozyme, which was probed by static and synchronous fluorescence spectroscopy. The quantification of the QD–lysozyme binding isotherm, exchange rate, and critical flocculation concentration was carried out. The core–shell QDs exhibited higher binding with lysozyme yielding a binding constant of K = 5.04 × 10⁹ L mol⁻¹ compared to the core-only structures (K = 6.16 × 10⁷ L mol⁻¹), and the main cause of binding was identified as being due to hydrophobic forces. In addition to the enzyme activity being dose dependent, it was also found that core–shell structures caused an enhancement in activity. Since binary QDs like CdSe also show a change in the lysozyme enzyme activity, therefore, a clear differential between binary and ternary QDs was required to be established which clearly revealed the relevance of surface chemistry on the QD–lysozyme interaction.

Eco-friendly synthesis of CIS and CIS@ZnS quantum dots was carried out, and their interaction with lysozyme revealed spontaneous and hydrophobic binding. Lysozyme helicity and enzymatic activity increased upon complexation.