Sustainable Bio-Based Adsorbents for Simultaneous and Efficient Removal of Hazardous Dyes from Aqueous Solutions.

Dyes provide a notable environmental issue as a result of their intrinsic poisonous and carcinogenic characteristics. An estimated 60,000 metric tons of dyes has been discharged into the environment, leading to a substantial increase in water pollution. The mitigation of these dyes is a substantial and intricate challenge. The primary objective of this research is to conduct a comprehensive analysis of the adsorption of cationic dyes containing positively charged groups such as sulphonates, amines, and triphenylmethanes. The adsorption study was carried out using four different low-cost adsorbents derived from biowaste, specifically Groundnut Shell (GS), Mosambi Peel (MP), Mango Bark (MBARK), and Mango Leaves (ML). The adsorbent materials were characterized using FTIR, UV-Vis spectroscopy, scanning electron microscopy (SEM), point-of-zero charge (PZC), and BET techniques. The adsorption capacity was found to be between 1.5 and 2.2 mg/gm for Groundnut Shell, Mosambi Peel, Mango Bark, and Mango Leaves for individual dye removal (Crystal violet, Methylene blue, Rhodamine B, and Malachite green). It was observed that adsorbent derived from mango bark showed excellent adsorption (%) in a mono-component dye system and, thus, was explored for the simultaneous removal of a mixture of the same dyes. MBARK exhibited an excellent overall dye removal efficiency of 94.44% (Qe = 2.7 mg/g) for the dye mixture in 60 min. From a detailed kinetic investigation, it was concluded that the adsorption followed the pseudo-second-order model (R2= 0.99963 to 1 for different dyes and adsorbents) hinting at chemisorption. The effect of the pH of the analyte solution and the dosage of adsorbent was also studied for simultaneous removal. The isothermal studies demonstrated that the Langmuir adsorption model (R2 = 0.99416) was the best-fitted model, suggesting monolayer adsorption. The adsorption process was predicted to be governed by ion exchange, electrostatic interaction, hydrogen bonding, pi-pi interaction, etc., based on charge, functional groups, and pH of dyes and adsorbent. Thus, this study highlights the application of low-cost biowaste as a potential adsorbent for the mitigation of toxic industrial dyes present in wastewater.

Structural properties and adsorption performance relationship towards three categories of lignin and their derived biochar.

The growing interest in utilizing lignin for dye removal has gained momentum, but there is limited information on the intricate relationship between lignin structural characteristics and adsorption efficacy, especially for its biochar derivatives. This study focused on three types of lignin and their corresponding biochar derivatives. Among them, ZnCl2-activated acidic/alkali densified lignin preparation of lignin-derived active carbon exhibited superior adsorption performance, achieving 526.32 mg/g for methylene blue and 2156.77 mg/g for congo red. Its exceptional adsorption capacity was attributed to its unique structural properties, including low alkyl and O-alkyl group content and high aromatic carbon levels. Furthermore, the adsorption mechanisms adhered to pseudo-second-order kinetics and the Langmuir model, signifying a spontaneous process. Intriguingly, lignin-derived active carbon also demonstrated remarkable recovery capabilities. These findings provide valuable insights into the impact of structural attributes on lignin and its biochar's adsorption performance.

Selective visual staining of polyurethane microplastics by novel colorimetric and near-infrared (NIR) fluorescent dye: Application to environmental water and natural soil samples.

Microplastics can cause environmental pollution and ecosystem destruction as well as human health problems. Among the types of microplastics, polyurethane (PU) is particularly resistant to heat and difficult to decompose, causing disposal problems, and is evaluated as one of the most hazardous polymers. We present a novel colorimetric and near-infrared (NIR) fluorescence dye, (E)-N-(2-((4-(diphenylamino)benzylidene)amino)phenyl)- 7-nitrobenzo[c][1,2,5]oxadiazol-4-amine (DPNA), designed for selective visual PU microplastic staining. The intramolecular charge transfer (ICT) properties of DPNA are demonstrated through density functional theory (DFT) calculations along with solvatochromic shift. DPNA exhibits red color and red fluorescence emission, showing promising potential as a staining dye. To achieve selective PU microplastic staining, we establish an optimized experimental procedure with the staining dye DPNA by evaluating the staining efficiency under different staining solvent compositions and staining times. DPNA can distinguish PU by both red fluorescence signal and red coloration among different types of microplastics. In addition, DPNA well stain fresh PUs with diverse sizes and at various pH range of 5-9, and the aged PUs can also be dyed as effectively as the fresh PU. Most importantly, DPNA selectively stains PU among 11 types of microplastics and 5 types of natural particles in environmental water and soil with and without any pre-treatments. The adsorption mechanism of DPNA on PU microplastic is demonstrated through field emission scanning electron microscopes (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and non-covalent interaction (NCI)-reduced density gradient (RDG) analyses, and proposed that intermolecular hydrogen bonding has a significant effect.

Rapid in-EPON CLEM: Combining fast and efficient labeling of self-labeling enzyme tags with EM-resistant Janelia Fluor dyes and StayGold.

Correlative light and electron microscopy (CLEM) combines light microscopy (LM) of fluorescent samples to ultrastructural analyses by electron microscopy (EM). Pre-embedding CLEM often suffers from inaccurate correlation between LM and EM modalities. Post-embedding CLEM enables precise registration of structures directly on EM sections, but requires fluorescent markers withstanding EM sample preparation, especially osmium tetroxide fixation, dehydration and EPON embedding. Most fluorescent proteins (FPs) lose their fluorescence during such conventional embedding (CE), but synthetic dyes represent promising alternatives as their stability exceeds those of FP. We analyzed various Janelia Fluor dyes and TMR conjugated to ligands for self-labeling enzymes, such as HaloTag, for fluorescence preservation after CE. We show that TMR, JF525, JF549, JFX549 and JFX554 retain fluorescence, with JFX549 and JFX554 yielding best results overall, also allowing integration of high-pressure freezing and freeze substitution. Furthermore, we found the recently published FP StayGold to resist CE, facilitating dual-fluorescence in-resin CLEM.

Facile synthesis of amino-modified magnetic covalent organic framework for the efficient extraction and determination of anionic azo dyes in carbonated beverages.

In this work, a novel magnetic covalent organic framework (COF (TpPa-NH2) @ Fe3O4) was prepared via two step by simple solvent method for the extraction of anionic azo dye residues in food. The as-prepared COF (TpPa-NH2) @ Fe3O4 nanocomposite was characterised by scanning electron microscope, transmission electron microscope, Fourier transform-infrared spectroscopy, X-ray diffraction and vibrating sample magnetometer. Before high-performance liquid chromatography with ultraviolet detection (HPLC-UV) determination, it was used as magnetic adsorbent for magnetic solid-phase extraction (MSPE) to extract and pre-concentrate three anionic azo dyes in carbonated beverage samples. The several key extraction and desorption parameters affecting the extraction recovery rate were investigated, including extraction time, pH of the solution, amount of material, adsorption time, elution solvent, pH of elution solvent, type of elution solvent, elution volume and elution time. Under optimised conditions, this method has good linearity between 5 and 500 µg L-1 (correlation coefficient > 0.9986). The limit of detection was 2.3-3.4 µg L-1. The recoveries of the samples were between 87.5 and 96.9%, and the relative standard deviation lower than 4.6%. The developed method has broad application prospects for the analysis of anionic azo dyes in carbonated beverages.

An ultra-small organic dye nanocluster for enhancing NIR-II imaging-guided surgery outcomes.

PURPOSE: The accuracy of surgery for patients with solid tumors can be greatly improved through fluorescence-guided surgery (FGS). However, existing FGS technologies have limitations due to their low penetration depth and sensitivity/selectivity, which are particularly prevalent in the relatively short imaging window (< 900 nm). A solution to these issues is near-infrared-II (NIR-II) FGS, which benefits from low autofluorescence and scattering under the long imaging window (> 900 nm). However, the inherent self-assembly of organic dyes has led to high accumulation in main organs, resulting in significant background signals and potential long-term toxicity. METHODS: We rationalize the donor structure of donor-acceptor-donor-based dyes to control the self-assembly process to form an ultra-small dye nanocluster, thus facilitating renal excretion and minimizing background signals. RESULTS: Our dye nanocluster can not only show clear vessel imaging, tumor and tumor sentinel lymph nodes definition, but also achieve high-performance NIR-II imaging-guided surgery of tumor-positive sentinel lymph nodes. CONCLUSION: In summary, our study demonstrates that the dye nanocluster-based NIR-II FGS has substantially improved outcomes for radical lymphadenectomy.

Preparation of novel Fe-containing zeolite-A for KN-R decolorization by Fenton-like reaction.

Herein, novel catalysts of Fe-containing zeolite-A (Fe/zeolite-A) were synthesized by exchanging iron ions into zeolite-A framework, and short-chain organic acids (SCOAs) were employed as chelating agents. Reactive Brilliant Blue KN-R (KN-R) was used as a model pollutant to evaluate the performance of these catalysts based on the heterogeneous Fenton reaction. The results showed that Fe-OA/3A, which applied zeolite-3A as the supporter and oxalic as the chelating agent, presented the most prominent KN-R decolorization efficiency. Under the initial pH of 2.5, 0.4 mM KN-R could be totally decolorized within 20 min. However, the mineralization efficiency of KN-R was only 58.2%. Therefore, anthraquinone dyes were introduced to modify zeolite-3A. As a result, the mineralization efficiency of KN-R was elevated to 92.7% when using Alizarin Violet (AV) as the modifier. Moreover, the modified catalysts exhibited excellent stability, the KN-R decolorization efficiency could be maintained above 95.0% within 20 min after operating for nine cycles. The mechanism revealed that the Fe(II)/Fe(III) cycle was accelerated by AV-modified catalyst thus prompting the KN-R decolorization in Fenton-like system. These findings provide new insights for preparing catalysts with excellent activity and stability for dye wastewater treatment.

Comparative analysis among the degradation potential of enzymes obtained from Escherichia coli against the toxicity of sulfur dyes through molecular docking.

The common bacterium Escherichia coli has demonstrated potential in the field of biodegradation. E. coli is naturally capable of biodegradation because it carries a variety of enzymes that are essential for the breakdown of different substances. The degradation process is effectively catalyzed by these enzymes. The collaborative effects of E. coli's aryl sulfotransferase, alkanesulfonate moonoxygenase, and azoreductase enzymes on the breakdown of sulfur dyes from industrial effluents are investigated in this work. ExPASY ProtParam was used to confirm the stability of the enzyme, showing an instability index less than 40. We determined the maximum binding affinities of these enzymes with sulfur dye pollutants - 1-naphthalenesulfonic acid, sulfogene, sulfur green 3, sulfur red 6, sulfur red 1, sulfur yellow 2, thianthrene, thiazone, and thional - using comparative molecular docking. Significantly, the highest binding affinity was shown by monooxygenase (-12.1), whereas aryl sulfotransferase and azoreductase demonstrated significant energies of -11.8 and -11.4, respectively. The interactions between proteins and ligands in the docked complexes were examined. To evaluate their combined effects, co-expression analysis of genes and enzyme bioengineering were carried out. Using aryl sulfotransferase, alkanesulfonate monooxygenase, and azoreductase, this study investigates the enzymatic degradation of sulfur dye pollutants, thereby promoting environmentally friendly and effective sulfur dye pollutant management.

Synthesis of New D-π-A Phenothiazine-Based Fluorescent Dyes: Aggregation Induced Emission and Antibacterial Activity.

Highly solid-state fluorescent dyes based on phenothiazine bearing sulfa-drug derivatives were successfully prepared and fully characterized by NMR, mass spectra, and elemental analysis. The prepared phenothiazine dyes bearing sulfadiazine and sulfathiazole 4-(((10-hexyl-10 H-phenothiazin-3-yl)methylene)amino)-N-(pyrimidin-2yl) benzenesulfonamide (PTZ-1) and 4-(((10-hexyl-10 H-phenothiazin-3-yl) methylene) amino)-N-(thiazol-2-yl)benzenesulfonamide (PTZ-2), showed strong emission in polycrystalline form, and significant emission in solution was observed. The quantum yield of the prepared dyes varied and decreased by increasing the solvent polarity, with the maximum recorded value being 0.63 and 0.6 in dioxane. Aggregation-induced emission (AIE) and the effect of the solvent polarity on absorption and emission spectra were investigated. The dyeing application of polyester fabrics using the prepared phenothiazine-based dyes was studied, showing very good affinity to dyed fabrics. The antibacterial affinity against gram-positive and gram-negative bacteria for the dye powder as well as the dyed PET fabric was investigated, with PTZ-2 showing better affinity against bacteria compared to PTZ-1. This multifunctional property highlights the potential uses of PTZ-1 and PTZ-2 for advanced applications in biomedicine and optoelectronics.

Development of natural dye photosensitizers for dye-sensitized solar cells: a review.

Dye-sensitized solar cell (DSSC) is a photovoltaic device that can be produced from natural source pigments or natural dyes. The selection of natural dyes for DSSC application is currently under research. The utilization of natural dye materials that are easy to obtain, cost-effective, and non-toxic can reduce waste during DSSC fabrication. Natural dyes can be extracted from plants through extraction and chromatography methods. The suitability and viability of utilizing natural dyes as photosensitizers in DSSCs can be predicted using appropriate software simulation by varying related parameters to produce high power conversion efficiency. In this context, the purpose of the review is to highlight the evolution of performance improvement in the development of DSSCs with consideration of natural dye extraction and software simulation. This review also focuses on the results of extracting natural dyes from herbal ingredients, which are still very limited in information, and several parts of herbal plants that can be used as natural dye sources in the future of solid-state DSSCs have been identified. Based on the results of this review, the highest efficiency was obtained for the DSSC that used chlorophyll pigments as natural dyes using Peltophorum pterocarpum leaves with 6.07%, followed by anthocyanin pigments as natural dyes using raspberries (black) fruits with 1.5%, flavonoid pigments as natural dyes using Curcuma longa herbs with 0.64%, and flavonoid pigments as natural dyes using Indigofera tinctoria flowers with 0.46%.

Amine response smartphone-based portable and intelligent polyvinyl alcohol films for real-time detection of shrimp freshness.

Food freshness monitoring is an important component in ensuring food safety for consumers and the food industry. Therefore, there is an urgent need for a portable, low-cost, and efficient detection method to determine the freshness. In this study, polyvinyl alcohol (PVA) was used as polymer carrier to prepare electrospinning film containing curcumin (Cur) and gardenia blue (GB) as intelligent indicator label on food packaging for real-time nondestructive detection of freshness of shrimp. The detection limit of ammonia response is less than or equal to 20 ppm, and the detection time is about 1 min, indicating that it has a sensitive response effect. At the same time, a smartphone application that can identify amines in response to color changes has been developed, and consumers can understand freshness by scanning the label. This study demonstrates the huge potential of smart indicator labels for food freshness monitoring.

Radiation-Assisted Assembly of a Highly Dispersed Nanomolybdenum-Functionalized Covalent Organic Framework.

Two-dimensional covalent organic frameworks (2D COFs), featuring a large surface area and 1D pore structure, serve as promising scaffolds for anchoring functional guest compounds, which can significantly enhance their performance and thus expand their potential applications. Postsynthetic strategy for COFs functionalization is versatile but challenging because of their tedious procedure with high time and energy consumption, generation of excess reaction waste, and damage to COF crystallinity. We report in this work a general strategy for the synthesis of inorganic nanocompound-functionalized COF composites in a one-pot way. Specifically, a high-crystallinity nanoscale molybdenum compound is successfully introduced into a COF skeleton with high dispersion in situ during the crystallization process of the COF induced by gamma ray radiation under ambient conditions. The obtained COF@Mo composites exhibit remarkable sorption performance for methylene blue and many other organic dyes in aqueous solution with the advantages of ultrarapid uptake dynamics and high removal efficiency.

Use of Unprecedented Intramolecular 1,3-Dipolar Cycloaddition Reaction in meso-Nitrile Oxide-Containing BODIPY as a New Pathway for the Preparation of Fused NIR Platforms.

Meso-nitrile oxide group in 1,7-Diphenyl-containing BODIPYs can be involved in highly unusual [3+2] intramolecular cycloaddition reaction with the formation of the dihydrobenzo[d]isoxazole-containing BODIPYs. Oxidation of these compounds results in the formation of unprecedented either benzisoxazole- or benzo[b]azepine-fused fully conjugated NIR absorbing BODIPYs. The photophysical properties and electronic structures of the target compounds were studied by an array of experimental and theoretical methods.

Confinement of a Styryl Dye into Nanoporous Aluminophosphates: Channels vs. Cavities.

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host-guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield.

Nanoremediation and Antioxidant Potential of Biogenic Silver Nanoparticles Synthesized Using Leucena's Leaves, Stem, and Fruits.

Synthetic dyes are persistent organic environmental pollutants that can cause extensive damage to living beings and to the ecosystem as a whole. Cost-effective, sustainable, and efficient strategies to deal with this type of pollution are necessary as it commonly resists conventional water treatment methods. Silver nanoparticles (AgNPs) synthesized using the aqueous extract from the leaves, stem, and fruits of Leucaena leucocephala (Leucena) were produced and characterized through UV-vis, TEM, EDS, SDL, XPS, XRD, and zeta potential, and they proved to be able to promote adsorption to remediate methylene blue and tartrazine pollution in water. The nanoremediation was performed and did not require direct exposure to sunlight or any special lamp or a specific reduction agent. The AgNPs produced using the extract from the leaves exhibited the best performance in nanoremediation and also presented antioxidant activity that surpassed the one from butylated hydroxytoluene (BHT). Consequently, it is an interesting nanotool to use in dye nanoremediation and/or as an antioxidant nanostructure.

PyrAtes: Modular Organic Salts with Large Stokes Shifts for Fluo-rescence Microscopy.

The deployment of small-molecule fluorescent agents plays an ever-growing role in medicine and drug development. Herein, we complement the portfolio of powerful fluorophores, reporting the serendipitous discovery and development of a novel class with an imidazo[1,2-a]pyridinium triflate core, which we term PyrAtes. These fluorophores are synthesized in a single step from readily available materials (>60 examples) and display Stokes shifts as large as 240 nm, while also reaching NIR-I emissions at λmax as long as 720 nm. Computational studies allow the development of a platform for the prediction of λmax and λEm. Furthermore, we demonstrate the compatibility of these novel fluorophores with live cell imaging in HEK293 cells, suggesting PyrAtes as potent intracellular markers.

Self-assembly of metal-polyphenolic network on biomass for enhanced organic contaminant capturing from water with a high cost-to-benefit ratio.

Nanomaterials present a vast potential as functional materials in environmental engineering. However, there are challenges with nanocomplex for recyclability, reliable/stable, and scale-up industrial integration. Here, a versatile, low-cost, stable and recycled easily metal-polyphenolic-based material carried by wood powder (bioCar-MPNs) adsorption platform was nano-engineered by a simple, fast self-assembly strategy, in which wood powder is an excellent substrate serving as a scaffold and stabilizer to prevent the nanocomplex from aggregating and is easier to recycle. Life cycle analysis highlights a green preparation process and environmental sustainability for bioCar-MPNs. The metal-polyphenolic nanocomplex coated on the wood surface in bioCar-MPNs presents a remarkable surface adsorption property (1829.4 mg/g) at a low cost (2.4 US dollars per 1000 g bioCar-MPNs) for organic dye. Quartz crystal microbalance analysis (QCM) demonstrates an existing strong affinity between polyphenols and organic dyes. Furthermore, Independent Gradient Model (IGM) and Hirshfeld surface analysis reveal the presence of the electrostatic interactions, π-π interactions, and hydrogen bonding. Meanwhile, adsorption efficiency of bioCar-MPNs maintains over 95% in the presence of co-existing ions (Na+, 0.5 M). Importantly, the reasonable utilization of biomass for water treatment can contribute to achieving the high-value and resource utilization of biomass materials.

Multiplexed colorimetry collaborated with smartphone-based image analysis for simultaneous and fast visualization of dyes in both environmental and food samples.

In this work, a multiplexed colorimetric strategy was initiated for simultaneous and fast visualization of dyes using low-cost and easy-to-prepare indicator papers as sorbents. Response surface methodology (RSM) was employed to model statistically and optimize the process variables for dyes extraction and colorimetric assays. Multiplexed colorimetry was realized by virtue of synchronous color alignments from different dimensions of multiple dyes co-stained colorimetric cards under RSM-optimized conditions, and smartphone-based image analysis was subsequently performed from different modes to double-check the credibility of colorimetric assays. As concept-to-proof trials, simultaneous visualization of dyes in both beverages and simulated dye effluents was experimentally proved with results highly matched to HPLC or spiked amounts at RSM-predicted staining time as short as 50 s ∼3 min, giving LODs as low as 0.97 ± 0.22/0.18 ± 0.08 µg/mL (tartrazine/brilliant blue) for multiplexed colorimetry, which much lower than those obtained by single colorimetry. Since this is the first case to propose such a RSM-guided multiplexed colorimetric concept, it will provide a reference for engineering of other all-in-one devices which can realize synchronous visualization applications within limited experimental steps.

2-Aryl-3H-1,3-benzazaphosphole Oxides: Synthesis, Optical Properties, and Excited State Intramolecular Proton Transfer.

Inclusion of a heteroatom to the phosphole ring is a promising strategy to intrinsically modulate the optical properties of phosphole derivatives. We report on a series of 2-aryl-3H-1,3-benzazaphosphole oxides that were efficiently prepared via sequential C-P cross-coupling, dehydrative [3 + 2] cycloaddition, and ring-oxidation reactions. The inclusion of one nitrogen atom into the benzophosphole framework caused red shifting of the absorption and emission maxima, reflecting the greater stabilization of the LUMO level. 2-(2-Hydroxyphenyl)benzazaphosphole oxide underwent excited state intramolecular proton transfer and emitted a weak fluorescence from the excited state of the N-H tautomer.

Illegal synthetic dyes in spices: a Singapore case study.

Some synthetic dyes are fraudulently added into spices to appeal visually to consumers. Food regulations in several countries, including the United States, Australia, Japan and the European Union, strictly prohibit the use of unauthorised synthetic dyes in food. Nevertheless, illegal practices persist, where spices contaminated with potentially carcinogenic dyes have been documented, posing potential health risks to consumers. In the present study, 14 synthetic dyes were investigated through liquid chromatography/tandem mass spectrometry in 252 commercially available spices in the Singapore market. In 18 out of these (7.1%) at least 1 illegal dye was detected at concentrations ranging from 0.010 to 114 mg/kg. Besides potential health risks, presence of these adulterants also reflects the economic motivations behind their fraudulent use. Findings in the present study further emphasise the need for increased public awareness, stricter enforcement, and continuous monitoring of illegal synthetic dyes in spices to ensure Singapore's food safety.