Small Dye Molecules Research Articles

Improving performance of SALDI-MS by regulating density of plasmonic nanoparticles

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) emerges as an effective method for analyzing small molecules. At the current stage, its application is still limited by its detection sensitivity. According to the mechanism of SALDI-MS, the sensitivity highly depends on the laser desorption/ionization (LDI) efficiency. In this study, we adjust the localized surface plasmon resonance (LSPR) between particles by changing the gap, thereby improving the efficiency of LDI. The gaps of nanoparticles can be adjusted by the ionic strength in the solution. With the decrease of the gaps, the thermal effect of the nanoparticles is gradually enhanced and the number of excited electrons is also increased, which improves the sensitivity of SALDI-MS. The prepared substrate with optimized gaps has wide applicability for the detection of small biomolecules and dye molecules. Moreover, the substrate can successfully detect trace small molecules in complex samples. The analysis of sulfonamide in lake water shows the commendable performance of the substrate. The relative standard deviations (RSD) of spot-to-spot and batch-to-batch are 3.73% and 7.22% respectively, confirming the high reproducibility and the detection limit is as low as 100 pM, indicating the high sensitivity of the substrate. The results demonstrate that adjusting the LSPR of metal nanoparticles is a promising method for improving the performance of SALDI-MS.

Central Ring Puckering Enhances the Stokes Shift of Xanthene Dyes.

Small-molecule dyes are generally designed based on well-understood electronic effects. However, steric hindrance can promote excited-state geometric relaxation, increasing the difference between the positions of absorption and emission bands (the Stokes shift). Accordingly, we hypothesized that sterically induced central ring puckering in xanthene dyes could be used to systematically increase their Stokes shift. Through a combined experimental/quantum-chemical approach, we screened a group of (9-acylimino)-pyronin dyes with a perturbed central ring geometry. Our results showed that an atom with sp3 hybridization in position 10 of (9-acylimino)-pyronins induces central ring puckering and facilitates excited-state geometric relaxation, thereby markedly enhancing their Stokes shifts (by up to ~2000 cm-1). Thus, we prepared fluorescent (9-acylimino)-pyronin pH sensors, which showed a Stokes shift disparity between acid and base forms of up to ~8700 cm-1. Moreover, the concept of ring puckering-enhanced Stokes shift can be applied to a wide range of xanthene analogues found in the literature. Therefore, central ring puckering may be reliably used as a strategy for enhancing Stokes shifts in the rational design of dyes.

Promoting the Near-Infrared-II Fluorescence of Diketopyrrolopyrrole-Based Dye for In Vivo Imaging via Donor Engineering.

Small-molecule dyes for fluorescence imaging in the second near-infrared region (NIR-II, 900-1880 nm) hold great promise in clinical applications. Constructing donor-acceptor-donor (D-A-D) architectures has been recognized to be a feasible strategy to achieve NIR-II fluorescence. However, the development of NIR-II dyes via such a scheme is hampered by the lack of high-performance electron acceptors and donors. Diketopyrrolopyrrole (DPP), as a classic organic optoelectronic material, enjoys strong light absorption, high fluorescence quantum yield (QY), and facile derivatization. Nevertheless, its application in the NIR-II imaging field has been hindered by its limited electron-withdrawing ability and the aggregation-caused quenching (ACQ) effect resulting from the planar structure of DPP. Herein, with DPP as an electron acceptor and through donor engineering, we have successfully designed and synthesized a DPP-based dye named T-27, in which the strong D-A interaction confers excellent NIR absorption and high-brightness NIR-II fluorescence tail emission. By strategically introducing long alkyl chains on the donor unit to increase intermolecular spacing and reduce the influence of solvent molecules, T-27 exhibits an improved anti-ACQ effect in aqueous solutions. After being encapsulated into DSPE-PEG2000, T-27 nanoparticles (NPs) show a relative NIR-II fluorescence QY of 3.4% in water, representing the highest value among the DPP-based NIR-II dyes reported to date. The outstanding photophysical properties of T-27 NPs enable multimode NIR-IIa bioimaging under 808 nm excitation. As such, the T-27 NPs can distinguish mouse femoral vein and artery and achieve cerebral vascular microscopic imaging with a penetrating depth of 800 μm, demonstrating the capability for high-resolution deep-tissue imaging. This work holds significant potential in the field of bioimaging and provides a new strategy for developing bright NIR-II dyes.

Effect of UV-absorbing small molecule dyes with different alkyl chain densities and branching positions on the photovoltaic performance of semitransparent DSSCs

To achieve dye-sensitized solar cells (DSSCs) with high transparency, multi-color capability, and long-term durability for future applications across various fields.

In situ confined encapsulation of ultrafine Fe2O3 nanoclusters in N/S co-doped graphene-based membranes for continuous chemical conversion.

Membranes with catalytic function can provide an effective approach for simultaneously transforming reactants to industrial chemicals and separation. However, rational design of stable and high-quality catalytic membranes with controlled structure remains a big challenge. We report a strategy for in situ confined encapsulation of ultrafine Fe2O3 nanoclusters in nitrogen and sulfur co-doped graphene-based membranes for continuous chemical conversion. By manipulation of the active ferric catalytic center and surrounding coordination atoms in doped rGO nanosheets, multiple coordination structures were provided to achieve improved catalytic properties. Angstrom-level confined interlayer structure (∼8 Å) was constructed by external pressurization of Fe/NS-rGO nanosheets on membrane substrate, and the adsorption energy of 4-nitrophenol (4-NP) molecule between Fe/NS-rGO layers was much stronger than that in traditional nanometer-level confined space due to extra interactions, achieving the catalytic efficiency with a high Turnover Frequency (TOF) value (1596.0 h-1). The prepared ultrathin Fe/NS-rGO catalytic membrane also exhibited excellent water flux and rejection rate for small dye molecules, as well as long-term separation activity toward naphthol green B (NgB) for at least 130 h. The progress offers a viable route to the rational design of high-quality catalytic membranes with tailored structures and properties for wide applications.

Two-dimensional graphene oxide/MXene lamellar membrane cross-linked by urea with adjustable interlayer spacing for efficient dye rejection and ion sieving

Two-dimensional (2D) membranes demonstrate good performance in molecular and ion separation due to their unique layer structure. However, the sieving performance of 2D membranes is severely limited by drawbacks such as poor stability and low mass transfer rates. Here, we propose a design strategy using urea as a cross-linking agent to construct stable and regular nanochannels inside the graphene oxide/MXene (GO/MXene) composite membranes. More importantly, by changing the composition, the effective interlayer spacing of the membrane can be easily adjusted within 4.47–8.92 Å with angstrom-level precision for tunable ion sieving. The composite membrane exhibits high water permeance (79.58 L m−2 h−1 bar−1) and excellent small molecule dye rejection (>99 %). Moreover, depending on the ionic valence state, the membrane exhibits significant ion sieving. The good Cl−/SO42− selectivity (11.64) makes it a promising alternative to conventional ion exchange membranes. This study demonstrates an innovative and facile way to construct 2D lamellar membranes with stable structures for efficient and precise separation.

Assessing Surface Adsorption in Cyclic Olefin Copolymer Microfluidic Devices Using Two-Dimensional Nano Liquid Chromatography-Micro Free Flow Electrophoresis Separations.

Surface interactions are a concern in microscale separations, where analyte adsorption can decrease the speed, sensitivity, and resolution otherwise achieved by miniaturization. Here, we functionally characterize the surface adsorption of hot-embossed cyclic olefin copolymer (COC) micro free-flow electrophoresis (μFFE) devices using two-dimensional nLC × μFFE separations, which introduce a 3- to 5 s plug of analyte into the device and measure temporal broadening that arises from surface interactions. COC is an attractive material for microfluidic devices, but little is known about its potential for surface adsorption in applications with continuous fluid flow and temporal measurements. Adsorption was minimal for three small molecule dyes: positively charged rhodamine 123, negatively charged fluorescein, and neutral rhodamine 110. Temporal peak widths for the three dyes ranged from 3 to 7 s and did not change significantly with increasing transit distance. Moderate adsorption was observed for Chromeo P503-labeled myoglobin and cytochrome c with temporal peak widths around 20 s. Overall, the COC surface adsorption was low compared to traditional glass devices, where peak widths are on the order of minutes. Improvements in durability, long-term performance, and ease of fabrication, combined with low overall adsorption, make the COC μFFE devices a practical choice for applications involving time-resolved continuous detection.

Relief of tumor hypoxia using a nanoenzyme amplifies NIR-II photoacoustic-guided photothermal therapy.

Hypoxia is a critical tumor microenvironment (TME) component. It significantly impacts tumor growth and metastasis and is known to be a major obstacle for cancer therapy. Integrating hypoxia modulation with imaging-based monitoring represents a promising strategy that holds the potential for enhancing tumor theranostics. Herein, a kind of nanoenzyme Prussian blue (PB) is synthesized as a metal-organic framework (MOF) to load the second near-infrared (NIR-II) small molecule dye IR1061, which could catalyze hydrogen peroxide to produce oxygen and provide a photothermal conversion element for photoacoustic imaging (PAI) and photothermal therapy (PTT). To enhance stability and biocompatibility, silica was used as a coating for an integrated nanoplatform (SPI). SPI was found to relieve the hypoxic nature of the TME effectively, thus suppressing tumor cell migration and downregulating the expression of heat shock protein 70 (HSP70), both of which led to an amplified NIR-II PTT effect in vitro and in vivo, guided by the NIR-II PAI. Furthermore, label-free multi-spectral PAI permitted the real-time evaluation of SPI as a putative tumor treatment. A clinical histological analysis confirmed the amplified treatment effect. Hence, SPI combined with PAI could offer a new approach for tumor diagnosing, treating, and monitoring.

HSA shrinkage optimizes the photostability of embedded dyes fundamentally to amplify their efficiency as photothermal materials

Focused on the performance promotion of organic small molecular dyes based photothermal agents via non-chemical modification, we found that heat-assisted binding of human serum albumin (HSA) to the dye causes shrinkage of the protein and encapsulate the dye to form nanoparticles. This revolutionizes the photostability of small molecule dyes which further improves their photothermal conversion efficiency and tumor ablation performance as photothermal agents significantly. In this work, the obtained photothermal agent named HSA-P2-T could accumulate in tumor and induce 22 °C enhancement of the tumor in xenograft models upon ultra-low dose (0.1 W/cm2) laser irradiation, which, as far as we know, is the lowest laser dose used in vivo photothermal therapy. Utilizing HSA-P2-T, we realized tumor ablation upon twice intravenous injections of the nanoparticles and four photothermal treatments.

Poloxamer 407 Combined with Polyvinylpyrrolidone To Prepare a High-Performance Poly(ether sulfone) Ultrafiltration Membrane.

At present, the design and fabrication of polymer membranes with high permeability and good retention ability are still huge challenges. In this study, the commercial Poloxamer 407 (Pluronic F127) is selected as a multifunctional additive, and polyvinylpyrrolidone is used as a pore-forming agent to modify the poly(ether sulfone) membrane by liquid-liquid phase conversion technology to prepare an ultrafiltration membrane with excellent performance. The hydrophobic poly(propylene oxide) segment in Poloxamer 407 guarantees that this copolymer can be firmly anchored to the poly(ether sulfone) matrix, and the hydrophilic poly(ethylene oxide) segments in Poloxamer 407 impart a stronger hydrophilic nature to the modified membrane surface. Therefore, the permeability and hydrophilicity of the modified membrane are significantly improved and the modified membrane also has good stability. When the amount of Poloxamer 407 added to the casting solution reached 0.6 g, the water flux of the modified membrane was as high as 368 L m-2 h-1, and the rejection rate of bovine serum albumin was close to 98%. In the test to isolate organic small molecule dyes, the retention rate of the modified membrane to Congo red is 94.27%. In addition, the modified membrane shows an excellent water flux recovery rate and antifouling ability. It performs well in subsequent cycle tests and long-term membrane life tests and can be used repeatedly. Our work has resulted in poly(ether sulfone) membranes with good performance, which show great potential in the treatment of biomedical wastewater and the removal of industrial organic dye wastewater, it provides ideas for the development and application of amphiphilic polymer materials.

Organic Dye Molecule Intercalated Vanadium Oxygen Hydrate Enables High-Performance Aqueous Zinc-Ion Storage.

Although the layered vanadium oxide-based materials have been considered to be one of the candidates for aqueous Zn-ion batteries (AZIBs), it still faces inevitable challenges of unsatisfactory capacities and sluggish kinetics because of strong electrostatic interactions between Zn-ions and structure lattice. This work addresses the strategy of pre-inserting guest materials to vanadium oxide cathode using different intercalants. To achieve this goal, the small organic dye molecules, methyl orange (MO), and methylene blue (MB) are proposed as the intercalants for vanadium oxygen hydrate (VOH). It has been demonstrated that use of these intercalants can facilitate reaction kinetics between Zn2+ and VOH, leading to an improvement of specific capacity (293mAhg-1 at 0.3Ag-1 for MO-VOH and 311mAhg-1 for MB-VOH) compared to VOH, a large enhancement of excellent energy density (237.1Whkg-1 for MO-VOH, 232.3Whkg-1 for MB-VOH), and a prolong lifespan operation at 3Ag-1 . The mechanism studies suggest that the weakened electrostatic interactions between the Zn-ions and V-O lattice after intercalating organic molecules contribute to boosting the electrochemical performance of AZIBs unveiled by charge density difference and binding energy.

Dye sieving and dye/salt separation PEI-based loose nanofiltration membrane modified by NH2-MIL-101(Fe) and polyphenol coating

Effective dye sieving and dye/salt separation could recycle valuable resources during textile wastewater treatment. In this work, a loose nanofiltration (NF) membrane with outstanding performance was constructed with facile materials including the surface polyphenol coating and the polyetherimide (PEI) support. Firstly, the mixed matrix support membrane was prepared by incorporating Fe-based MOF NH2-MIL-101(Fe) into PEI membrane via non-solvent induced phase separation (NIPS) method, then the polyphenol coating based on vanillyl alcohol, which was the characteristic component derived from Gastrodia elata Blume, was co-deposited on the support PEI membrane, followed by the treatment of 1,3-propane sultone. In this way, the optimal loose NF membrane could have a high good pure water permeability (87.9 L·m−2·h−1·bar−1) while high dye/salt selectivity was reached (Selectivity: 58.9 for Congo Red/NaCl; 46.8 for Conge Red/Na2SO4). Moreover, a mixture of large molecule dye and small molecule dye could be sieved and the optimal loose NF membrane showed outstanding antifouling capacity with the flux recovery ratio of 85.7%, 98.1%, and 97.9% respectively for bovine serum albumin (BSA), sodium alginate (SA), and humic acid (HA), which was further analyzed and calculated by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The long-term stability during EBT/Na2SO4 mixture filtration endowed the membrane with great potential in treating textile wastewater.

Selenadiazolesbenzothiadiazole‐Based Small Donor–Acceptor–Donor Dye for Photothermal Therapy in NIR‐II Window

AbstractRecently, photothermal therapy (PTT) has attracted enormous attention because of its low invasiveness, high spatiotemporal selectivity, and good therapeutic effect. Different types of photothermal conversion agents have been developed, particularly the second near‐infrared window (NIR‐II, 1000–1700 nm) organic small molecular dyes which have become an attractive research direction. Herein, a novel and simple donor–acceptor–donor (D–A–D) type NIR‐II dye SeC is designed and synthesized with 2λ4δ2‐[1,2,5]selenadiazolo[3,4‐f]‐2,1,3‐benzothiadiazole structure. To improve capability of SeC for biomedical applications, SeC molecules are encapsulated into DSPE‐PEG2000 to construct nanoparticles SeC‐NPs, which show high photostability and biocompatibility. More importantly, SeC‐NPs exhibited an excellent photothermal performance and display high photothermal conversion efficiency (PCE) of 62% under 808 nm excitation. Because of favorable fluorescence property in NIR‐II window and high PCE, SeC‐NPs are successfully used for NIR‐II imaging and PTT of 4T1 tumor‐bearing mice models. In vivo studies demonstrate SeC‐NPs’ ability to suppress tumor growth under NIR photoirradiation without visible damage to main organs. Overall, this study develops a strategy to design a simple small molecule dye containing selenium for NIR‐II imaging, and SeC‐NPs shows high performance for PTT toward tumor.

Silk nanofibrils-MOF composite membranes for pollutant removal from water

Membrane separation technology is considered an effective strategy to remove pollutants in sewage. However, it remains a significant challenge to fabricate inexpensive membranes with high purification efficiency. Therefore, the present study proposes the integration of silk nanofibrils (SNFs) and polydopamine⊂metal-organic framework (PDA⊂MOF) nanoparticles to prepare self-supporting membranes, which can effectively intercept nanoparticle pollutants through the size exclusion effect and can strongly adsorb organic dyes and metal ions by SNF. In addition, PDA⊂MOF enables these membranes to adsorb small molecules and heavy metal ions during the filtration process, thereby effectively removing various pollutants from sewage. The integration of size-exclusion and adsorption capabilities enables the SNF/PDA⊂MOF membrane to remove nanoparticles, small-molecule dyes, heavy metal ions, and radioactive elements. This work provides a rational approach for the design and development of the next generation of water treatment membranes and is expected to be used in environmental, food-related, and biomedical fields.

Design of novel organoboron small-molecule dyes based on dipolar nitrogen-boron-nitrogen unit for solution-processed photovoltaic devices

The nitrogen-boron-nitrogen (N–B–N) structure combined with strong polar B–N and B←N bonds simultaneously, opens a new window for the development of organoboron photovoltaic materials with narrow band gap and low highest occupied molecular orbital (HOMO) energy level. In this paper, two N–B–N-embedded blocks including boron dipyrromethane (BODIPY) and double B–N bridged bipyridyl (BNBP), are exploited to rationally regulate the band gap and energy level of the resulting material by virtue of their strong electron affinities. Thus, the thiophene as a weak electron-donating part is directly attached to strong electron-withdrawing BODIPY and BNBP respectively, giving much improved photoelectric properties for such simple push-pull architectures. To further improve photoelectric and thermal properties of the material, two novel extended D-π-A-π-D-type organoboron molecules namely BDPTPA and BNBPTPA, in which BODIPY and BNBP as strong electron-deficient core (A) connect strong electron-rich triphenylamine (D) via thiophene π-spacer, are synthesized by Stille reaction between BODIPY/BNBP and “π-D” segment. Therefore, BDPTPA exhibits a preferable electrochemical band gap as small as 1.36 eV close to near-infrared (NIR) region, which is one of the lowest values among the BODIPY-based small-molecule donors (SMDs). Furthermore, BNBPTPA shows stronger light absorption of up to 1.16 × 105 M−1 cm−1, deeper HOMO energy level of −5.28 eV and very excellent thermal stability (Td = 428 °C). It is mentioning that, BNBPTPA is first used as SMD material, blending with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) for solution-processed organic solar cell. Consequently, a reasonable power conversion efficiency (PCE) of 6.78% has been achieved with a satisfactory short-circuit density (Jsc) of 17.27 mA cm−2 and open-circuit voltage (Voc) of 0.87 V, which is the highest efficiency for BNBP-based SMDs so far. Our work demonstrates that a proposed molecular design and synthesis with dipolar N–B–N-containing unit and “π-D” fragment, can greatly broaden the types of new photovoltaic donor materials.

Novel Biomass-Based Polymeric Dyes: Preparation and Performance Assessment in the Dyeing of Biomass-Derived Aldehyde-Tanned Leather.

High-performance chrome-free leather production is currently one of the most concerning needs to warrant the sustainable development of the leather industry due to the serious chrome pollution. Driven by these research challenges, this work explores using biobased polymeric dyes (BPDs) based on dialdehyde starch and reactive small-molecule dye (reactive red 180, RD-180) as novel dyeing agents for leather tanned using a chrome-free, biomass-derived aldehyde tanning agent (BAT). FTIR, 1H NMR, XPS, and UV-visible spectrometry analyses indicated that a Schiff base structure was generated between the aldehyde group of dialdehyde starch (DST) and the amino group of RD-180, resulting in the successful load of RD-180 on DST to produce BPD. The BPD could first penetrate the BAT-tanned leather efficiently and then be deposited on the leather matrix, thus exhibiting a high uptake ratio. Compared with the crust leathers prepared using a conventional anionic dye (CAD), dyeing, and RD-180 dyeing, the BPD-dyed crust leather not only had better coloring uniformity and fastness but it also showed a higher tensile strength, elongation at break, and fullness. These data suggest that BPD has the potential to be used as a novel sustainable polymeric dye for the high-performance dyeing of organically tanned chrome-free leather, which is paramount to ensuring and promoting the sustainable development of the leather industry.

Facilely prepare high-performance loose nanofiltration membranes through regulation of polymer chain entanglements

The membrane forming process was fundamentally affected by the thermodynamics of polymer solution, the core of which involved the governance of polymer chain entanglements in the solution. In this work, a high-performance loose nanofiltration (LNF) membrane with high water permeance and high separation accuracy was facilely fabricated by the regulation of polymer chain entanglements through only changing CaCO3 nanoparticle (nano-CaCO3) size in the casting solution. The degree of polymer chain entanglements was characterized by the critical entanglement viscosity of the casting solution. The solution viscosity was markedly increased with the decrease of nano-CaCO3 size and then significantly reduced when nano-CaCO3 disappeared. While the mutual diffusion rate between the non-solvent (acidic water) and the solvent was increased to bring about rapid phase inversion with increasing the viscosity of the casting solution. The high solution viscosity and rapid phase inversion, which was a unconventional phenomenon, leaded to the formation of LNF membranes with outstanding performance. The LNF membranes obtained had a pore diameter of 1.4 nm (MWCO = 1625 Da) and a high pure water permeance of 98 L·m−2·h−1·bar−1, accompanying an excellent separation accuracy of small molecule dyes and NaCl mixtures (the rejection is 99.9% for eriochrome black T (EBT, Mw = 461 Da) and 4.5% for NaCl). This work provides general guidance for the structural regulation of high-performance separation membranes.

Three Generations of Surface Nanocomposites Based on Hexagonally Ordered Gold Nanoparticle Layers and Their Application for Surface-Enhanced Raman Spectroscopy

The fabrication technology of surface nanocomposites based on hexagonally ordered gold nanoparticle (AuNP) layers (quasi-arrays) and their possible application as surface-enhanced Raman spectroscopy (SERS) substrates are presented in this paper. The nanoparticle layers are prepared using a nanotextured template formed by porous anodic alumina (PAA) and combined with gold thin-film deposition and subsequent solid-state dewetting. Three types of hexagonal arrangements were prepared with different D/D0 values (where D is the interparticle gap, and D0 is the diameter of the ellipsoidal particles) on a large surface area (~cm2 range), namely, 0.65 ± 0.12, 0.33 ± 0.10 and 0.21 ± 0.09. The transfer of the particle arrangements to transparent substrates was optimized through three generations, and the advantages and disadvantages of each transfer technology are discussed in detail. Such densely packed nanoparticle arrangements with high hot-spot density and tunable interparticle gaps are very beneficial for SERS applications, as demonstrated with two practical examples. The substrate-based enhancement factor of the nanocomposites was determined experimentally using a DNA monolayer and was found to be between 4 × 104 and 2 × 106 for the different particle arrangements. We also determined the sensing characteristics of a small dye molecule, rhodamine 6G (R6G). By optimizing the experimental conditions (e.g., optimizing the laser power and the refractive index of the measurement medium with an ethylene-glycol/water mixture), concentrations as low as 10−16 M could be detected at 633 nm excitation.

Superior performance of novel chitosan-based flocculants in decolorization of anionic dyes: Responses of flocculation performance to flocculant molecular structures and hydrophobicity and flocculation mechanism

To achieve economical and efficient decolorization, two novel flocculants, weakly hydrophobic comb-like chitosan-graft-poly (N, N-Dimethylacrylamide) (CSPD) and strongly hydrophobic chain-like chitosan-graft-L-Cyclohexylglycine (CSLC) were synthesized in this study. To assess the effectiveness and application of CSPD and CSLC, the impacts of factors, including flocculant dosages, initial pH, initial dye concentrations, co-existing inorganic ions and turbidities, on the decolorization performance were explored. The results suggested that the optimum decolorizing efficiencies of the five anionic dyes ranged from 83.17% to 99.40%. Moreover, for accurately controlling flocculation performance, the responses to flocculant molecular structures and hydrophobicity in flocculation using CSPD and CSLC were studied. The Comb-like structure gives CSPD a wider dosage range for effective decolorization and better efficiencies with large molecule dyes under weak alkaline conditions. The strong hydrophobicity makes CSLC more effective in decolorization and more suitable for removing small molecule dyes under weak alkaline conditions. Meanwhile, the responses of removal efficiency and floc size to flocculant hydrophobicity are more sensitive. Mechanism studies revealed that charge neutralization, hydrogen bonding and hydrophobic association worked together in the decolorization of CSPD and CSLC. This study has provided meaningful guidance for developing flocculants in the treatment of diverse printing and dyeing wastewater.

Highly selective imaging of intratumoral hydrogen sulfide by NIR-II emissive fluorescent probes

Hydrogen sulfide (H2S) is an important signaling molecule that exists in a variety of tissues and has important effects on various physiological functions of the human body. Studies have shown that chronic kidney disease, liver cirrhosis and cardiovascular disease are closely related to abnormal levels of H2S in the body. In addition, endogenous H2S is closely associated with a variety of cancers and can be regarded as a biomarker for specific cancers. In this study, we have successfully designed a rhodamine hybrid polymethine-based small molecule dye (FL-NO2), whose fluorescence in the second near-infrared window (NIR-II, 900–1700 nm) can be dramatically enhanced after exposure to H2S. After being encapsulated by amphiphilic polymer F-127, the obtained water-soluble nanoparticles (n-FL-NO2) can be used for the sensitive detection of H2S in the NIR-II region, which provides large penetration depth and high signal-to-noise ratio. The probe also exhibited high selectivity towards H2S, avoiding interference from multiple biothiols. The detection of endogenous H2S in vivo was demonstrated with a colon cancer model, which expressed a high level of H2S. In summary, this study provides a promising NIR-II fluorescent probe for the rapid detection of H2S, which may become an effective tool for disease diagnosis.