Diketopyrrolopyrrole Amphiphile-Based Micelle-Like Fluorescent Nanoparticles for Selective and Sensitive Detection of Mercury(II) Ions in Water

Rapidly and simply detecting Cr (VI) in aqueous media via a diketopyrrolopyrrole-based chemosensor with both high selectivity and low LOD

BACKGROUND

The high toxicity of hexavalent chromium [Cr (VI)] could not only cause harmful effects on humans, including carcinogenicity, respiratory issues, genetic damage, and skin irritation, but also contaminate drinking water sources, aquatic ecosystems, and soil, impairing the reproductive capacity, growth, and survival of organisms. Due to these harmful effects, detecting toxic Cr (VI) is of great significance. However, the rapid, simple, and efficient detection at a low Cr (VI) concentration is extremely challenging, especially in an acidic condition (existing as HCrO4-) due to its low adsorption free energy.

RESULTS

A diketopyrrolopyrrole-based small molecule (DPPT-PhSMe) is designed and characterized to act as a chemosensor, which allows a high selectivity to Cr (VI) at an acidic condition with a low limit of detection to 10-8 M that is two orders of magnitude lower than the cut of limit (1 μM) recommended by World Health Organization (WHO). Mechanism study indicates that the rich sulfur atoms enhance the affinity to HCrO4-. Combining with favorable features of diketopyrrolopyrrole, DPPT-PhSMe not only allows dual-mode detection (colorimetric and spectroscopic) to Cr (VI), but also enables disposable paper-based sensor for naked-eye detection to Cr (VI) from fully aqueous media. The investigation of DPPT-PhSMe chemosensor for the quantification of Cr (VI) in real life samples demonstrates a high reliability and accuracy with an average percentage recovery of 102.1 % ± 4 (n = 3).

SIGNIFICANCE

DPPT-PhSMe represents the first diketopyrrolopyrrole-derived chemosensor for efficient detection to toxic Cr (VI), not only providing a targeted solution to the bottleneck of Cr (VI) detection in acidic conditions (existing as HCrO4-) caused by its low adsorption free energy, but also opening a new scenario for simple, selective, and efficient Cr (VI) detection with conjugated dye molecules.

Triphenylamine-Based Polythioacetal for Selective Sensing of Mercury(II) with High Specificity and Sensitivity

Utilizing the mercury (Hg2+)-triggered deprotection of thioacetals to aldehyde groups, we constructed a water-soluble triphenylamine (TPA)-based polythioacetal PTA-TPA with thioacetal groups in the backbones for efficient sensing of Hg2+ in aqueous solutions. PTA-TPA is conveniently prepared by polycondensation of 3, 6-dioxa-1,8-octanedithiol (DODT) with 4-(N,N-diphenylamino) benzaldehyde (TPA-CHO) using thiol-terminated mPEG2k-SH as a capping agent. The interaction of Hg2+ with PTA-TPA activates the aggregation-induced emission (AIE) process of TPA-CHO molecules, which makes the emission enhanced, and the emission color changes to sky blue, while other metal ions do not interfere with the sensing process. PTA-TPA can be used as a highly selective and ultrafast detection system for Hg2+ with a low detection limit (LOD) of 9.88 nM and a fast response of less than 1 min. In addition, the prepared test strips report the presence of Hg2+ with an LOD as low as 1 × 10-5 M. Intracellular imaging applications have demonstrated that PTA-TPA acts as a biocompatible fluorescent probe for efficient Hg2+ sensing in HeLa cells. Overall, the PTA-TPA fluorescence probes have the characteristics of easy synthesis, cost-effective, ultrafast detection speed, high selectivity, and high sensitivity, which can be used in practical applications.

Enzyme-free and rapid visual quantitative detection for pesticide residues utilizing portable smartphone integrated paper sensor

Serious toxicity for organisms from pesticide glyphosate (Gly) residues to the ecosystem and human health has become a consensus. Rapid and selective detection of glyphosate, especially using a simple and portable instrument, is highly desired. In this work, we develop a novel enzyme-free rapid and visual ratiometric fluorescence sensor for selectively quantitative detecting glyphosate by integrating the designed blue carbon nanodots (CDs) and gold nanoclusters (Au NCs). The fluorescence of CDs can be quickly quenched via aggregation-caused quenching (ACQ) within 2 s after introducing glyphosate, resulting from the formation of CDs-Gly-CDs complex aggregation. While the Au NCs serve as the reference signal without any change, therefore leading to obvious and instant ratiometric fluorescence variation from blue to pink to orange. The broad linear range was obtained from 0 to 180 nM with a satisfactory detection limit of 4.19 nM. Furthermore, this approach was successfully applied to detect glyphosate in real samples and a portable smartphone platform integrated paper sensor was developed for in-site visual quantitative glyphosate detection, offering a promising strategy for the construction of enzyme-free trace hazard detection system.

Biothiol-Functionalized Cuprous Oxide Sensor for Dual-Mode Sensitive Hg2+ Detection

Hg²⁺ ions are one of the highly poisonous heavy metal ions in the environment, so it is urgent to develop rapid and sensitive detection platforms for detecting Hg²⁺ ions. In this work, a novel electrochemical and photoelectrochemical dual-mode sensor (l-Cys-Cu₂O) was successfully fabricated, and the sensor exhibits a satisfactory detection limit (0.2 and 0.01 nM) for the detection of Hg²⁺, which is far below the dangerous limit of the U.S. Environmental Protection Agency. The linear ranges of dual-mode Hg²⁺ detections were 0.33-3.3 and 0.17-1.33 μM, respectively. Moreover, the sensor shows desirable stability, selectivity, and reproducibility for detecting Hg²⁺ ions. For river water samples, the recoveries of 96.6-101.4% (electrochemical data) and 93.0-105.6% (photoelectrochemical data) were obtained, indicating that the sensor could be successfully applied in the determination of Hg²⁺ ions in environmental water. Therefore, the designed sensor has a potential in the trace-level detection of Hg²⁺ ions.

Thiophene-Bipyridine Appended Diketopyrrolopyrrole Ligands and Platinum(II) Complexes

Straightforward palladium(II) catalyzed direct cross-coupling reaction between decyl, (S)-2-methyl-butyl, and dodecyl N-substituted diketopyrrolopyrrole thiophene (DPPT), including a 3-methoxy-thiophene derivative, and 6-bromo-2,2'-bipyridine afforded a series of mono- and bis-bipyridine substituted DPPT ligands 1-3. Complexation reactions with PtCl₂(DMSO)₂ provided ortho-metalated platinum(II) complexes 1-Pt and 2-Pt, together with the N^N^O complex 3d-Pt(N^N^O) resulted from the O-Me activation of the intermediary complex 3d-Pt(N^N). The ligand 1b and the mononuclear complexes 1a-Pt and 1b-Pt have been structurally characterized by single crystal X-ray structure, evidencing the establishment of numerous intermolecular π-π interactions in the solid state. Moreover, in the crystal structure of the model complex DMTB-Pt(N^N^O) (DMTB = 3,4-dimethoxy-(2,2'-bipyridine)) the chelating tridentate N^N^O mode is clearly evidenced. The chiral ligand 1b and its mononuclear complex 1b-Pt do not show any CD signal in solution, but they are CD active in the solid state with bisignate bands in the low energy region, opposite in sign between the ligand and the complex, suggesting helical supramolecular arrangement of the dpp chromophore in the solid state. Photophysical investigations demonstrate that all of the ligands are fluorescent with high quantum yields, while the emission is quenched for the complexes, except partially in 3d-Pt(N^N), very likely through an intersystem crossing mechanism promoted by the heavy metal. Density functional theory calculations support the differences observed between the absorption properties of the ligands, ortho- and non-ortho-metalated complexes. The highly fluorescent bipyridine ligands reported herein open the way toward multifunctional transition metal complexes and their use in organic electronics.

Single-Atom Switching as a General Approach to Designing Colorimetric and Fluorogenic Probes for Mercury Ions

By performing a single-atom replacement within common fluorophores, we have developed a facile and general strategy to prepare a broad-spectrum class of colorimetric and fluorogenic probes for the selective detection of mercury ions in aqueous environments. Thionation of carbonyl groups from existing fluorophore cores results in a great reduction of fluorescence quantum yield and loss of fluorescence emission. The resulting thiocaged probes are efficiently desulfurized to their oxo derivatives in the presence of mercury ions, leading to pronounced changes in chromogenic and fluorogenic signals. Because these probes exhibit high selectivity, excellent sensitivity, good membrane-permeability, and rapid responses towards mercury ions, they are suitable for visualization of mercury in both aqueous and intracellular environments.

Facile fabrication of self-reporting micellar and vesicular structures based on an etching-ion exchange strategy of photonic composite spheres of poly(ionic liquid)

Micellar and vesicular structures capable of sensing and reporting the chemical environment as well as facilely introducing user-defined functions make a vital contribution to constructing versatile compartmentalized systems. Herein, by combining poly(ionic liquid)-based photonic spheres and an etching-ion exchange strategy we fabricate micellar and vesicular photonic compartments that can not only mimic the structure and function of conventional micelles and vesicles, but also sense and report the chemical environment as well as introducing user-defined functions. Photonic composite spheres composed of a SiO2 template and poly(ionic liquid) are employed to selectively etch outer-shell SiO2 followed by ion exchange and removal of the residual SiO2 to afford micellar photonic compartments (MPCs). The MPCs can selectively absorb solvents from the oil/water mixtures together with sensing and reporting the adsorbed solvents by the self-reporting optical signal associated with the uniform porous structure of photonic spheres. Vesicular photonic compartments (VPCs) are fabricated via selective infiltration and polymerization of ionic liquids followed by etching of the SiO2 template. Subsequent ion exchange introduces desirable functions to the VPCs. Furthermore, we demonstrate that the thickness and the anisotropic functions of VPCs can be facilely modulated. Overall, we anticipate that the micellar and vesicular photonic compartments with self-reporting optical signals and user-defined functions could serve as novel platforms towards multifunctional compartmentalized systems.

Figure-eight arylene ethynylene macrocycles: facile synthesis and specific binding behavior toward Hg2+

Two figure-eight arylene ethynylene macrocycles (AEMs) were synthesized from non-helical precursors and the figure-eight shape was clearly imaged by STM.

Reusable, facile, and rapid aptasensor capable of online determination of trace mercury

Herein, we reported a homemade waveguide-based evanescent wave aptasensor for the facile online monitoring of mercury pollution. The aptasensor exploited the high selectivity of hairpin structure-based thymidine-Hg²⁺-thymidine coordination chemistry (T-T mismatch) for Hg²⁺ recognition and the stably regenerable capability of DNA-functionalized waveguide surfaces. The presence of Hg²⁺ caused the T-T mismatch of Cy5.5-labeled T-rich single-stranded DNA sequences. The formed hairpin structures blocked the further hybridization of T-rich single-stranded DNA sequences with the complementary DNA strands that are modified on the waveguide surface; this phenomenon was accompanied by the decrease in the fluorescent signals excited by the evanescent wave. The limit of detection in real water samples was determined to be 0.2 μg/L, which was comparable with that of 0.4 μg/L in an ultrapure water under controlled conditions. And the linear range was observed from 1.4 µg/L to 240.7 µg/L. The negligible environmental matrix effect on the performance ensured the reliability of the proposed aptasensor. Moreover, the cross reactivity of this method toward other investigated metal ions was negligible. Through the delicate surface modification with DNA molecules covalently, the chip was reused at least 31 times with a relative standard deviation (RSD) of less than 19%. A Hg²⁺ pollution accident was successfully detected within 30 min, shedding new light in pollution monitoring, environment restoration, and emergency treatment.

A review on nanostructure-based mercury (II) detection and monitoring focusing on aptamer and oligonucleotide biosensors

Heavy metal ion pollution is a severe problem in environmental protection and especially in human health due to their bioaccumulation in organisms. Mercury (II) (Hg²⁺), even at low concentrations, can lead to DNA damage and give permanent harm to the central nervous system by easily passing through biological membranes. Therefore, sensitive detection and monitoring of Hg²⁺ is of particular interest with significant specificity. In this review, aptamer-based strategies in combination with nanostructures as well as several other strategies to solve addressed problems in sensor development for Hg²⁺ are discussed in detail. In particular, the analytical performance of different aptamer and oligonucleotide-based strategies using different signal improvement approaches based on nanoparticles were compared within each strategy and in between. Although quite a number of the suggested methodologies analyzed in this review fulfills the standard requirements, further development is still needed on real sample analysis and analytical performance parameters.

Pyridine-Diketopyrrolopyrrole-Based Novel Metal-Free Visible-Light Organophotoredox Catalyst for Atom-Transfer Radical Polymerization

In the field of electronics, organocatalysts are in high demand for use in the synthesis of clean polymers using solar radiation rather than potentially contaminating metals. Combining theoretical design, simulation, and experiments, this work presents a novel, pyridine-diketopyrrolopyrrole (P-DPP)-based metal-free visible-light organophotoredox catalyst (P-DPP). It is effective in the photocontrolled organocatalytic atom-transfer radical polymerization (O-ATRP) of methyl methacrylate (MMA) and styrene. The use of this catalyst and white light-emitting diode (LED) irradiation produces polymers with a cross-linked feature. In O-ATRP, the P-DPP catalyst has an oxidative quenching catalytic mechanism with an excited-state reductive potential of -1.8 V, fluorescence lifetime of 7.5 ns, and radical-cation oxidative potential of 0.45 V. Through molecular simulation, we found that the adjacent pyridine group is key to reducing the alkyl halide initiator and generating radicals, while the diketopyrrolopyrrole core stabilizes the triplet state of the catalyst through intramolecular charge transfer. The findings related to this novel photoredox catalyst will aid in the search for much more effective organophotoredox catalysts for use in controlled radical polymerization. They will also be of value in the fields of polymer chemistry and physics and in various applications.

A Sensitive Isoniazid Capped Silver Nanoparticles - Selective Colorimetric Fluorescent Sensor for Hg2+ Ions in Aqueous Medium

Novel isonicotinic acid hydrazide functionalized silver nanoparticles (INH-AgNPs) were synthesized by wet chemical method and used for the detection of Hg²⁺ ions in aqueous medium. The INH-AgNPs exhibit good absorbance and emission peaks by sensing Hg²⁺ ions with visible color changes. The detection of Hg²⁺ ions was confirmed by FT-IR, EDAX spectra and by the changing morphology of INH-AgNPs, and after addition of Hg²⁺ was confirmed by SEM and TEM imaging studies. Based on the emission intensity the probe INH-AgNPs exhibit a lowest detection limit (LOD) of Hg²⁺ to 0.18 nM. The association constant (K_a) of INH-AgNPs + Hg²⁺ ions is calculated using the Bensei-Hildebrand equation. Also, the probe is successfully utilized for the detection of Hg²⁺ ions in real water samples obtained from different fields, which showed good results.

Visual detection of Hg2+ by manipulation of pyocyanin biosynthesis through the Hg2+-dependent transcriptional activator MerR in microbial cells

Mercury pollution has always been a huge threat to human health due to its significant toxicity. Thus, it's the continuing goal to obtain new mercury detection techniques that are cost-effective, operational stable, performance efficient, and applicable to the environmental and biological milieus. In this research, the soluble pigment pyocyanin with anti-bacterial and anti-fungal activities, the biosynthesis pathway of which was engineered under the regulation of Hg²⁺-dependent transcriptional activator MerR, was firstly used as the visual detection signal in the whole-cell biosensor. The engineered biosensor displayed optical sensing window and a good linearity for Hg²⁺ in the range of 25-1000 nM, and the detection limit could reach as low as 10 nM. It permitted on-site detection of bioavailable Hg²⁺ with extraordinary selectivity and could resist the interferences of extra metal ions. What's more, the developed biosensor performed function well in a wide pH range (pH 4-10) as well as the environmental water. By fully imitating and utilizing the biosystems from nature, the engineered colorimetric biosensor has great economic and performance advantages over most chemosensors as well as whole-cell biosensors in the practical application of detecting Hg²⁺ in the contaminated aquatic systems.

Construction of an effective ratiometric fluorescent sensing platform for specific and visual detection of mercury ions based on target-triggered the inhibition on inner filter effect

Sensitive and selective determination of mercury ion (Hg²⁺) is critical for human health and environmental monitoring. Herein we construct an effective ratiometric fluorescent sensing platform by combining green fluorescent polymer carbon dots (PCDs) and red fluorescent tetraphenylporphyrin tetrasulfonic acid hydrate (TPPS) for specific and visual detection of Hg²⁺. The fluorescence of PCDs can be quenched by TPPS through inner filter effect (IEF). In the presence of both Mn²⁺ and Hg²⁺, however, Hg²⁺ can expedite the complexation of TPPS and Mn²⁺, which causes the decrease in both fluorescence and absorption of TPPS, accompanied by the fluorescence recovery of PCDs due to the subdued IFE between TPPS and PCDs. Based on the change of fluorescence signal, a ratiometric fluorescent sensing platform is constructed for specific and visual detection of Hg²⁺. The proposed approach presents a fine linear range for Hg²⁺ over the range of 10-200 nM with a detection limit of 0.038 nM. Moreover, an easily distinguishable fluorescence color change from pink to green with the increase of Hg²⁺ concentration can be observed by the naked eye under a UV lamp. Such a simple and effective method shows great potential for visual sensing of Hg²⁺ in on-site and resource-limited settings.

Fluorescent organic nanoparticles (FONs) as convenient probes for metal ion detection in aqueous medium

Fluorescent organic nanoparticle (FON)-based chemosensors are emerging as a valuable tool for the fast and accurate detection of metal ions in aqueous media. In this review, we highlight the recent developments in this field.

A colorimetric paper sensor for visual detection of mercury ions constructed with dual-emission carbon dots

A ratiometric fluorescence nanosensor has been developed by mixing blue fluorescent carbon dots and red fluorescent carbon dots, where the blue fluorescence can be selectively quenched by Hg²⁺, while the red fluorescence is an internal reference.

Hydrophobicity-guided self-assembled particles of silver nanoclusters with aggregation-induced emission and their use in sensing and bioimaging

Hydrophobicity-guided self-assembled particles of silver nanoclusters with aggregation-induced emission were fabricated and used in sensing and bioimaging.

Recent advances in iridium(iii) complex-assisted nanomaterials for biological applications

Phosphorescent iridium(iii) complexes have gained increasing attention in biological applications owing to their excellent photophysical properties and efficient transportation into live cells.

A Target-Lighted dsDNA-Indicator for High-Performance Monitoring of Mercury Pollution and Its Antagonists Screening

As well-known, the excessive discharge of heavy-metal mercury not only destroys the ecological environment, bust also leads to severe damage of human health after ingestion via drinking and bioaccumulation of food chains, and mercury ion (Hg²⁺) is designated as one of most prevalent toxic metal ions in drinking water. Thus, the high-performance monitoring of mercury pollution is necessary. Functional nucleic acids have been widely used as recognition probes in biochemical sensing. In this work, a carbazole derivative, ethyl-4-[3,6-bis(1-methyl-4-vinylpyridium iodine)-9H-carbazol -9-yl)] butanoate (EBCB), has been synthesized and found as a target-lighted DNA fluorescent indicator. As a proof-of-concept, Hg²⁺ detection was carried out based on EBCB and Hg²⁺-mediated conformation transformation of a designed DNA probe. By comparison with conventional nucleic acid indicators, EBCB held excellent advantages, such as minimal background interference and maximal sensitivity. Outstanding detection capabilities were displayed, especially including simple operation (add-and-read manner), ultrarapidity (30 s), and low detection limit (0.82 nM). Furthermore, based on these advantages, the potential for high-performance screening of mercury antagonists was also demonstrated by the fluorescence change of EBCB. Therefore, we believe that this work is meaningful in pollution monitoring, environment restoration and emergency treatment, and may pave a way to apply EBCB as an ideal signal transducer for development of high-performance sensing strategies.