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In this work, solid-surface fluorescence spectra of Rhodamine B (RhB) and fluorescein (FLU), two extensively used fluorophores, were studied and their concentrations were semi-quantitatively determined using the three-dimensional excitation–emission matrix (3D-EEM) data. In order to measure the solid fluorescence spectra, a trace amount of fluorophores was physically adsorbed on a piece of filter paper as a fluorescent paper, and the fluorescence spectra were recorded from the surface of the fluorescent paper instead of the inner parts of the solution. The spectral measurement was performed utilizing a routine spectrofluorimeter designed to measure the fluorescence of solution only by placing the fluorescent paper in a simple handmade holder at an adjusted incident angle of radiation. The results revealed a significant increase in the fluorescence intensity of the fluorescent paper strip compared to the solution phase. Moreover, in the RhB–FLU paper strip the forster resonance energy transfer was observed between FLU and RhB, similar to the observed phenomenon in the solution phase. For quantifying fluorophores, the EEM data were successfully resolved by applying multivariate partial least squares and parallel factor analysis (PARAFAC) modeling, and the results were compared with the univariate method. This study may provide a general guideline in further developing the solid fluorescence measurement of concentrated solutions or solid samples that have fluorescence measurement limitations such as high self-absorption and highly scattered spectra by using a conventional spectrofluorimeter, and also of biological samples where a trace amount of the analyte is available and high sensitivity is required. [ABSTRACT FROM AUTHOR]

Fluorescent sensors with single reading are generally subject to unpredictable disturbs from environmental and artificial factors. In order to overcome this barrier of detection reliability, a paper-based optical sensor with proportional fluorescence was established and further combined with a smartphone for visual, on-site and quantitative detection of Fe3+, which affects the color, smell and taste of water, and endangers the health of plants and animals. The ratio fluorescent probe was fabricated by rhodamine B and carbon quantum dots derived from xylan. The red fluorescence of rhodamine B was inert to Fe3+, which was referred to as background. And blue emitting carbon quantum dots functioned as signal report units, which would be quenched by Fe3+ and make the fluorescence of the ratio probe change from purple to red. The quantitative detection of Fe3+ was conducted by investigating the RGB value of fluorescent images with a smartphone. With the increase of Fe3+ concentration, the R/B (red/blue) value of the fluorescent paper gradually increased. The linear detection range was 10–180 μM, and the limit of detection was 198.2 nM. The application of ratio fluorescent paper with a smartphone provides a facile method for the rapid detection of ions. [ABSTRACT FROM AUTHOR]

The surface-enhanced Raman scattering (SERS) properties of low-dimensional semiconducting MXene nanoflakes have been investigated over the last decade. Despite this fact, the relationship between the surface characteristics and SERSing performance of a MXene layer has yet to be comprehensively investigated and elucidated. This work shows the importance of surface morphology on the overall SERS effect by studying few-layer Ti3C2Tx MXene-based SERS substrates fabricated by vacuum-assisted filtration (VAF) and spray coating on filter paper. The VAF deposition results in a dense MXene layer suitable for SERS with high spot-to-spot and substrate-to-substrate reproducibility, with a significant limit of detection (LoD) of 20 nM for Rhodamine B analyte. The spray-coated MXenes film revealed lower uniformity, with a LoD of 50 nM for drop-casted analytes. Moreover, we concluded that the distribution of the analyte deposited onto the MXene layer is affected by the presence of MXene aggregates created during the deposition of the MXene layer. Accumulation of the analyte molecules in the vicinity of MXene aggregates was observed for drop-casted deposition of the analyte, which affects the resulting SERS enhancement. Ti3C2Tx MXene layers deposited on filter paper by VAF offer great potential as a cost-effective, easy-to-manufacture, yet robust, platform for sensing applications. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots (CQDs) and rhodamine B (RhB) were physically mixed to construct a highly selective and sensitive ratiometric fluorescent sensor (CQDs@RhB) for the quantitative and visual detection of Hg2+. After adding Hg2+, the emission peak of CQDs at 445 nm was quenched and the peak of RhB at 575 nm remained unchanged; the ratio of the two emission peaks had a linear relationship with the Hg2+ concentration. The CQDs@RhB had a detection range of 0–15 µM and the limit of detection (LOD) is 65.93 nM and a color change from blue to pink was visible to the naked eye under ultraviolet light. The study revealed a static quenching mechanism of CQDs@RhB. The established method was successfully applied to the detection of Hg2+ in real water and rice samples with satisfactory results. In addition, a portable fluorescent paper-based sensor platform was developed using computer software assistance. The relationship with Hg2+ concentration was constructed by converting the pictures obtained under ultraviolet light to RGB color mode for visualization and quantitative detection of Hg2+. This study provides a valuable strategy for constructing a rapid detection system for Hg2+ in the field. [ABSTRACT FROM AUTHOR]

[Display omitted] • FeCu@BC catalysts were synthesized using a simple one-step pyrolysis method. • FeCu@BC 600-2 exhibited good magnetic separation ability and excellent reusability. • The synergistic effect of Fe 3 O 4 , Cu0 and Biochar maintains high RhB removal. • Key ROS involves •OH at pH 3, and •OH and 1O 2 at pH 7, respectively. • sp2 C = C in biochar and Cu(I) from Cu0 facilitated the reduction of Fe(III) Treating the wastes generated from pulp and paper mills, such as black liquor and Fenton sludge is challenging. In this study, the biochar-supported Fe-Cu bimetallic catalysts were synthesized by a one-step pyrolysis method using Fenton sludge as iron source, acid-precipitated black liquor (APBL) as carbon source and copper nitrate as copper source. The catalysts were used to remove rhodamine B (RhB) dye from aqueous solution by Fenton-like reaction. The optimal catalyst (FeCu@BC 600-2) was pyrolyzed at 600 °C with an Fe/Cu mixing ratio of 2 and consisted of mesoporous biochar supported nanoscale Fe 3 O 4 and Cu0. It had a specific surface area of 104.6 m2·g−1 and a saturation magnetization of 33.3 emu·g−1. In the FeCu@BC 600-2 /H 2 O 2 system, RhB dye (10 mg·L-1) was completely removed within 60 min at acidic pH (initial pH 3, 0.2 g·L-1 catalyst, 1 mM H 2 O 2) or 6 h at neutral pH (initial pH 7, 0.25 g·L-1 catalyst, 25 mM H 2 O 2) at 30 °C. Moreover, the FeCu@BC 600-2 exhibited good magnetic separation ability, low metal leaching, excellent reusability and broad applicability to other synthetic dyes. The dye removal mechanism involved the synergistic effect of adsorption and catalytic oxidation (especially heterogeneous catalytic oxidation). At acidic pH, RhB degradation was due to •OH radical, which was generated from the activation of H 2 O 2 by ≡Cu(I) or Cu(I) oxidized from Cu0 and ≡Fe(II) in Fe 3 O 4. At neutral pH, RhB degradation was mainly due to •OH and 1O 2 with the former being produced by ≡Cu(I) and ≡Fe(II). Furthermore, Cu(I) oxidized from Cu0 and the active functional groups (such as sp2 C = C) in the biochar facilitated the reduction of Fe(III) to Fe(II), resulting in a high catalytic oxidation efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] The O-vacancy Bi 2 WO 6 /SrTiO 3 heterojunction photocatalyst with Z scheme photogenerated electron transfer mechanism was loaded on cellulose fibers to construct a visible light-responsive photocatalytic composite paper for efficient and recyclable degradation of organic dyes in water. The introduction of O vacancies in Bi 2 WO 6 by alkali etching increased the utilization rate of Bi 2 WO 6 for visible light and achieved effective regulation of the energy band structure and Fermi level, which transformed Bi 2 WO 6 /SrTiO 3 type-II heterojunction into Z scheme heterojunction. The light-excited electrons in the conduction band of O-vacancy Bi 2 WO 6 directly migrated to the valence band of SrTiO 3 , which improved the separation efficiency of photogenerated carriers and maximized the redox capability of semiconductors. Compared with other control papers, O-vacancy Bi 2 WO 6 /SrTiO 3 paper exhibited the best photocatalytic performance, and its degradation rate for rhodamine B could reach 71.1% under 100 min of Xe lamp irradiation. The O-vacancy Bi 2 WO 6 /SrTiO 3 paper also showed good photocatalytic cycle stability. Loading heterojunction on the cellulose fibers solved the problem of poor reusability and difficult in recovery for powder semiconductor photocatalyst in practical applications. This study provides a novel strategy for constructing Z scheme heterogeneity on cellulose fibers to prepare composite paper with high photocatalytic activity and good reusability. [ABSTRACT FROM AUTHOR]

The textile industry is one of the most important industries in the European Union. The main environmental problems of the textile industry are the high water consumption, the generated pollution, the variety of chemicals used and the high energy demand. Recently, adsorbents with a large specific surface area and low weight, such as aerogels, have attracted great interest as promising materials for removing dyes from polluted water. Cellulose aerogels are inexpensive and non-toxic. Langmuir and Freundlich isotherms were chosen as the best method to describe the performance of the adsorbent. In this study, the adsorption efficiency of Congo red, Naphthol green B, Rhodamine B and Methylene blue were determined by using an adsorbent synthesized from paper and cardboard waste. The total organic carbon concentration was chosen as an indicator of the concentration of the dyes in the solutions. The aerogel capsules had 5% cellulose content. It was found that the adsorption capacity of the aerogel in the solutions of Congo red varied from 0.028 mg/g to 14.483 mg/g; in the solutions of Naphthol green B, from 0.013 mg/g to 7.698 mg/g; in the solutions of Rhodamine B, from 0.020 mg/g to 8.768 mg/g; and in the solutions of Methylene blue, from 0.024 mg/g to 13.538 mg/g. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots (CQDs) and rhodamine B (RhB) were physically mixed to construct a highly selective and sensitive ratiometric fluorescent sensor (CQDs@RhB) for the quantitative and visual detection of Hg2+. After adding Hg2+, the emission peak of CQDs at 445 nm was quenched and the peak of RhB at 575 nm remained unchanged; the ratio of the two emission peaks had a linear relationship with the Hg2+ concentration. The CQDs@RhB had a detection range of 0–15 µM and the limit of detection (LOD) is 65.93 nM and a color change from blue to pink was visible to the naked eye under ultraviolet light. The study revealed a static quenching mechanism of CQDs@RhB. The established method was successfully applied to the detection of Hg2+ in real water and rice samples with satisfactory results. In addition, a portable fluorescent paper-based sensor platform was developed using computer software assistance. The relationship with Hg2+ concentration was constructed by converting the pictures obtained under ultraviolet light to RGB color mode for visualization and quantitative detection of Hg2+. This study provides a valuable strategy for constructing a rapid detection system for Hg2+ in the field. [ABSTRACT FROM AUTHOR]

A novel platform of a polydiacetylene combined with rhodamine B (PDA-Rho) colorimetric chemosensor array was prepared from a diacetylene monomer and rhodamine B derivative. Rhodamine B derivative as the ion-recognition element was embedded in the polydiacetylene matrix. To fabricate chemosensor, diacetylene monomer connected rhodamine B derivatives (DA-Rho) was coated onto a filter paper surface via drop-casting technique and transformed to polydiacetylene by polymerisation through ultraviolet (UV) irradiation. From the result, PDA-Rhoen exhibited high sensitivity and selectivity for Au3+ and could be monitored directly by naked eyes providing a fast, portable and easy-to-use as a molecular device in the real system. The DFT calculation results showed a stable complex between PDA-Rho and Au3+. We believe that, this method offers a sensitive and accurate process for Au3+ ion detection in real environmental and biological applications. [ABSTRACT FROM AUTHOR]

Continuous waste discharge into natural water resources in many countries is a severe global issue, and seeking an effective solution is a researcher's concern. Herein, toilet paper waste was a low-cost precursor for preparing carbon nanoparticles (TPCNPs). The characterization of TPCNPs revealed a 30 nm to 50 nm particle size, a 264 m2 g−1 surface area, and a cubical graphite lattice XRD pattern. The TPCNPs were tested for removing malachite green (MG), indigo carmine (IC), rhodamine B (RB), and methylene blue (MB) dyes from water. The solution parameters were examined for the sorption process, and a pH of 5.0 suited the MB removal, while a pH of 6.0 was suitable for MG, IC, and RB. The effect of concentration investigation showed an adsorption capacity of 110.9, 64.8, 73.5, and 98 mg g−1 for MG, IC, RB, and MB, respectively. The sorption of the four dyes fitted the Langmuir isotherm model; it was exothermic and spontaneous. The water remediation was tested using groundwater and seawater samples (GW and SW) spiked with pollutants. It is worth mentioning that one treatment sufficed for the remediation of GW and SW contaminated by 5 mg L−1 concentration, while a double treatment was required for 10 mg L−1 pollution in both samples. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (Ag NPs) were fabricated on the fibers of the filter paper by the reaction between silver nitrate (AgNO 3 ) and hydrazine hydrate (N 2 H 4 ·H 2 O). By using the Ag NPs-coated paper, the limit of detection as low as 10 − 11 M for Rhodamine B (RhB) and 10 − 10 M for crystal violet (CV) was achieved. Moreover, the uniformity, reproducibility and stability of the Ag NPs-coated paper were also involved. Meanwhile, the detection of 10 − 4 –10 − 6 M moxifloxacin in deionized water and tap water was also carried out successfully by using the paper-based substrates. The fabrication process is easy to handle, cost-efficient and the as-prepared paper-based SERS substrate is ideal for rapid and simple detection of low-abundance molecules. [ABSTRACT FROM AUTHOR]

An ultra-sensitive paper-based molecularly imprinted sensor for detection of H5N1 was described. The results can not only be detected quantitatively by fluorescence, but also can be directly read with naked eyes under visible light or ultraviolet light within 10 min. With naked eye detection, its sensitivity is obviously better than that of commercial kits. In particular, the cost of the sensor is cheap (Original size: RMB 1.53 Yuan each; Smaller size: RMB 0.08 Yuan each), which is beneficial to application. [Display omitted] • Paper-based molecularly imprinted sensor; • Ultra-sensitive detection of H5N1 (LOD, 0.58 fM); • Rapid visual detection of influenza H5N1 within 10 min; • More intuitive and sensitive results than commercially available kit; • Low cost (Original size, 1.53 yuan/piece; Smaller size, 0.08 yuan/piece). The rapid detection of pathogens is important to the control of epidemics. Here, a paper-based molecularly imprinted sensor has been developed for the visual detection of influenza H5N1 virus. Firstly, the paper-based molecularly imprinted was prepared by a sol–gel reaction. Then, H5N1 ∼ Apt was covalently bound to the surface of the ZIF-8-NH 2 coated with rhodamine B (RhB) through an amide bond, to produce the fluorescent and colorimetric probe ZIF-8-NH 2 @RhB ∼ Apt. When H5N1 and ZIF-8-NH 2 @RhB ∼ Apt are added to the paper-based MIPs, the H5N1 will be combined with MIPs through the synergistic effects of shape and size compatibility and interaction with the functional groups of the monomers, and ZIF-8-NH 2 @RhB ∼ Apt will bind to H5N1 through its aptamers to form a sandwich structure. The sensor has ultra-high sensitivity and the detection limit is 0.58 fmol/L by using fluorescence spectroscopy. A semi-quantitative signal can also be observed with the naked eye within 10 min. A comparative study showed that direct visual detection was highly reliable, and the sensitivity was better than that achieved with a commercially available kit. Importantly, the paper-based sensor is low in produce cost (Original size: RMB 1.53 Yuan each; Smaller size: RMB 0.08 Yuan each) and is easy to cut, store and carry. This sensor is expected to allow self-service, visual, high-throughput, and real-time virus detection, which is of great significance for epidemic prevention and control. [ABSTRACT FROM AUTHOR]

A rhodamine‐based colorimetric and fluorescent pH chemosensor (RhA) was designed and synthesized via a coupling reaction between rhodamine ethylenediamine and succinic anhydride. RhA showed excellent pH response in aqueous solutions. In addition, common cations (Na+, K+, Ag+, Mg2+, Ca2+, Pb2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Al3+, Cr3+, Fe3+, Au3+, Pt2+, and Ru2+) did not interfere with the pH response. As it has the potential to be used as a portable pH sensor, RhA was immobilized on activated cellulose paper using N,N'‐dicyclohexylcarbodiimide (DCC) and N,N'‐dimethylpyridin‐4‐amine (DMAP) as the coupling reagent to obtain a composite pH sensor (CP‐RhA). CP‐RhA was characterized by ATR‐FTIR, UV–vis, and fluorescence spectroscopy, and by scanning electron microscopy (SEM). CP‐RhA showed a rapid response in the pH range 1–8 through color and fluorescence changes. DFT calculations showed a blue‐shifted spectrum in the protonated form compared to the neutral form. Moreover, the pH sensor paper could be reused by dipping in NaOH. Thus, our work demonstrates the potential of the rhodamine dye composite for visualizing pH changes in real systems. [ABSTRACT FROM AUTHOR]

The precise detection of pathogenic microorganisms is crucial for the reduction of water-borne diseases. Herein, a filter-paper-based florescent chemosensor was fabricated for the detection of Escherichia coli and Staphylococcus aureus contamination exploiting protein-DNA interaction between the target and a specific probe. The sensing mechanism involved the self-assembly of Rhodamine B (RhB) on silver nanoparticles (AgNPs) surface that was labeled with a single-stranded DNA probe. This causes the fluorescence quenching of RhB by a distant-dependant process. The hybridization between pathogen-specific probe and bacterial surface protein causes the release of fluorescence of RhB, which was observed under UV light. For paper-based bio-surface preparation, the mixture comprising RhB-AgNP-ssDNA was drop-casted on filter paper discs. The conditions were optimized using isolated genomic DNA of the microbes. The method was applied for E.coli detection using an eae gene-based probe targeting intimin protein and S. aureus detection using tuf gene-based probe targeting EF-tuf protein on the microbe's surface. The chemosensor had a notable specificity and selectivity for E.coli, and S. aureus, with detection limits of 0.6 × 108 and 0.37 × 103 CFU/mL respectively. Moreover, the sensor was tested on real water samples, which presented excellent reproducibility of results (RSD ≤ 0.24%). Furthermore, the gradient change of fluorescence was captured by a smartphone, which allows direct detection of pathogens in a sensitive semi-quantitative way without the need for expensive instruments. The designed chemosensor can serve as a simple, inexpensive, and rapid method for the on-site detection of microbial contamination in drinking water. [ABSTRACT FROM AUTHOR]

Abstract: Acquisition of reproducible surface-enhanced Raman scattering (SERS) signals using paper-based SERS sensors is difficult because of the non-uniformity of the paper surface, which possesses a large number of pores and high surface roughness. To overcome the poor reproducibility of paper-based SERS sensors, they were coated with cellulose nanofibrils (CNF) obtained from pulp fibers, which fill the pores and decrease the local height differences on the paper’s surface. The combination of hydrophobic modification and the improved uniformity and smoothness of the surface after CNF coating increased the coverage of silver nanoparticles (AgNPs) in the SERS spots from 87 to 95% and gave a more uniform distribution of the AgNPs on the SERS substrate. When a high magnification lens was used for sensitive molecular detection, the hydrophobic CNF-coated paper-based SERS sensor reduced the relative standard deviation of the SERS intensity and improved the limit of detection for rhodamine 6G. The CNF coating on paper was found to afford a more effective and reproducible paper-based SERS sensor than conventional filter paper.Graphical Abstract: [ABSTRACT FROM AUTHOR]

A cellulose‐based photocatalytic membrane was fabricated by in situ growth of the NH2‐MIL‐125 nanoparticles onto the surfaces of the ultrathin titania (TiO2) gel layers pre‐coated cellulose nanofibres of natural cellulose substance (commercial laboratory filter paper). The NH2‐MIL‐125 nanoparticles were grown on the surface of the titania gel coated cellulose nanofibres via a one‐step solvothermal method. The resultant composite membranes maintained the initial hierarchical network structures of the bulk cellulose substance, consisting titania gel layer coated cellulose nanofibres with NH2‐MIL‐125 nanoparticles anchored on the surfaces. Owing to the hierarchical porous structure of the cellulose substrates as well as the effective heterostructure formation between the NH2‐MIL‐125 particles and the TiO2 layers, the composites showed enhanced photocatalytic performances. The NH2‐MIL‐125/TiO2/cellulose composite composed of 15.82 wt% NH2‐MIL‐125 content with nanoparticles sizes of 100–200 nm showed an apparent rate constant of 0.032 min−1 in photocatalytic degradation of Rhodamine B (RhB), which was higher than those of the NH2‐MIL‐125/cellulose composite and the TiO2/cellulose composite. It was demonstrated that pre‐coating of the cellulose nanofibres with ultrathin titania gel layers was essential for the growth of the NH2‐MIL‐125 nanoparticles thereon. [ABSTRACT FROM AUTHOR]

Synthetic cannabinoids are one of the many substances of abuse widely spreading in modern society. Medical practitioners and law enforcement alike highly seek portable, efficient, and reliable tools for on-site detection and diagnostics. Here, we propose a colorimetric lateral flow assay (LFA) combined with dye-loaded polymersome to detect the synthetic cannabinoid JWH-073 efficiently. Rhodamine B–loaded polymersome was conjugated to antibodies and fully characterized. Two LFA were proposed (sandwich and competitive), showing a high level of sensitivity with a limit of detection (LOD) reaching 0.53 and 0.31 ng/mL, respectively. The competitive assay was further analyzed by fluorescence, where the LOD reached 0.16 ng/mL. The application of the LFA over spiked synthetic saliva or real human saliva demonstrated an overall response of 94% for the sandwich assay and 97% for the competitive LFA. The selectivity of the system was assessed in the presence of various interferents. The analytical performance of the LFA system showed a coefficient of variation below 6%. The current LFA system appears as a plausible system for non-invasive detection of substance abuse and shows promise for synthetic cannabinoid on-site sensing. [ABSTRACT FROM AUTHOR]

In recent years, organic room‐temperature phosphorescence (RTP) has been widely investigated owing to its fascinating afterglow characteristics. Consequently, it has been applied in anti‐counterfeiting and information security. However, these applications are limited by cost, substrates, and technological processes. Hence, a simple and environmentally friendly adsorption‐induced RTP system containing sulfonic acid groups is designed for convenient and efficient application. A pure organic compound of (1,1″‐biphenyl)‐4,4″‐disulfonic acid can be easily ionized and dispersed in water. When it is adsorbed on different types of paper and cloth substrates rich in hydroxyl groups, bright RTP emissions with maximum lifetimes of ≈1.1 s are achieved after drying the substrates. The destructive effect of H2O on the intermolecular hydrogen bonds between the phosphor and substrates makes the RTP emissions responsive to the stimuli of water and heat. Furthermore, a white afterglow is realized after doping with Rhodamine B for energy transfer. On the account of the adsorption‐induced RTP effect, four economical applications are demonstrated, wherein one dollar's worth of the phosphor can be used for anti‐counterfeiting 7692 banknotes, printing and dyeing 1538 graphs on cloth, making 196 Chinese knots, and producing 385 writes of encryption information, promoting the further development and commercialization of RTP materials. [ABSTRACT FROM AUTHOR]

In this work, zinc oxide (ZnO) and titanium dioxide (TiO2) nanostructures were grown on different cellulose paper substrates, namely, Whatman, office, and commercial hospital papers, using a hydrothermal method assisted by microwave irradiation. Pure ZnO and TiO2 nanostructures were synthesized; however, the growth of TiO2 above ZnO was also investigated to produce a uniform heterostructure. Continuous ZnO nanorod arrays were grown on Whatman and hospital papers; however, on office paper, the formation of nanoplates originating nanoflower structures could be observed. TiO2 nanoparticles homogeneously covered all the substrates, in some conditions forming uniform TiO2 films. Structural characterization was carried out by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy. The optical characterization of all the materials was carried out. The produced materials were investigated for multifunctional applications, like photocatalyst agents, bacterial inactivators, and ultraviolet (UV) sensors. To evaluate the photocatalytic activity under UV and solar radiations, rhodamine B was the model-test contaminant indicator and the best photocatalytic activity was achieved with Whatman paper. Hospital paper with TiO2 nanoparticles showed significant antibacterial properties against Staphylococcus aureus. ZnO-based UV sensors demonstrated a responsivity of 0.61 μA W-1. [ABSTRACT FROM AUTHOR]

The surface-enhanced Raman scattering (SERS) properties of low-dimensional semiconducting MXene nanoflakes have been investigated over the last decade. Despite this fact, the relationship between the surface characteristics and SERSing performance of a MXene layer has yet to be comprehensively investigated and elucidated. This work shows the importance of surface morphology on the overall SERS effect by studying few-layer Ti3C2Tx MXene-based SERS substrates fabricated by vacuum-assisted filtration (VAF) and spray coating on filter paper. The VAF deposition results in a dense MXene layer suitable for SERS with high spot-to-spot and substrate-to-substrate reproducibility, with a significant limit of detection (LoD) of 20 nM for Rhodamine B analyte. The spray-coated MXenes film revealed lower uniformity, with a LoD of 50 nM for drop-casted analytes. Moreover, we concluded that the distribution of the analyte deposited onto the MXene layer is affected by the presence of MXene aggregates created during the deposition of the MXene layer. Accumulation of the analyte molecules in the vicinity of MXene aggregates was observed for drop-casted deposition of the analyte, which affects the resulting SERS enhancement. Ti3C2Tx MXene layers deposited on filter paper by VAF offer great potential as a cost-effective, easy-to-manufacture, yet robust, platform for sensing applications.

Electrokinetic stacking (ES) is effective for improving sensitivity of paper-based analytical device (PAD) for charged analytes. In this paper, we successfully demonstrated ES of electrically neutral analytes on PAD, and the performance was characterized by smartphone-based colorimetry and fluorescence. Firstly, SDS from cathode reservoir stacked as a micelle band on an open paper fluidic channel by ES, and the target analyte was swept by the micelle. Meanwhile, the probes at the other side were carried by electroosmotic flow (EOF). Eventually, neutral components preloaded on the channel were concentrated as the narrow stacking band. Taking the rhodamine B as a probe, the effects of EOF, background electrolyte concentration and anionic surfactant concentration were investigated. Fluorescence detection of rhodamine B and colorimetric analysis of Sudan III demonstrated the sensitivity enhanced and its potential for the semi-quantitative test. Under the optimized conditions, fluorescence detection limit of 50 nM of rhodamine B was achieved with a linear range of 1.0–10 μM (R 2 = 0.99). The colorimetric detection limit for Sudan III was 5.2 μM and the linear range was 5–40 μM (R 2 = 0.99). Compared with direct analysis without stacking, the signal levels of rhodamine B and Sudan III were increased by 30-fold and 6-fold, respectively. This study showed that with ES, sensitive and rapid PAD detection of electrically neutral analytes could be achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • New Schiff base sensor R4P developed using Rhodamine B fluorophore. • Highly sensitive and selective towards Al3+/Cu2+ in two solvent systems. • Low LOD, high K A , good anti-interference and reversibility properties. • Fabrication of strip for on-site detection using chromatography paper. • Low cytotoxicity of R4P makes it suitable for bio-imaging studies. In order to create a new Schiff base sensor R4P , rhodamine B hydrazide was directly combined with 4-propoxybenzaldehyde. The structure of this new sensor was completely revealed by spectroscopic methods, and a single crystal that could be used for X-ray diffraction techniques was produced. Under a UV lamp, the colourless and non-fluorescent R4P solution exhibits an orange fluorescence enhancement when Al3+ is present and showed a pink colour change when Cu2+ is present. Spectroscopic tools like UV, fluorescence, MS and NMR spectroscopy were used to study the recognition performance and complexation process of the sensor. The findings demonstrated that sensor R4P , with a limit of detection as low as 10-8 M and an association constant of ×104 M−1, is highly sensitive and selective towards both Al3+ and Cu2+ in two different solvent systems. Additionally, the designed system had a reasonable recovery range of above 89% for Al3+ and Cu2+ in two chosen water samples of natural mineral water and tap water. Moreover, a paper-based test strip that can detect target metal ions both colorimetrically and fluorometrically was created utilising chromatography paper. Aside from that, R4P 's minimal cytotoxicity marks it appropriate for bio-imaging studies on metal ion sensing using the fluorescence response in the HCT 116 cell line. [ABSTRACT FROM AUTHOR]

An analytical method combining fatty acid-emulsification liquid-liquid microextraction (FA-ELLME) with solidification of floating drops (SFD) and droplet digital image colorimetry (DDIC) was developed for the analysis of rhodamine B (RhB) in food and beverage samples. This work applied an emulsified amphiphilic fatty acid as an extracting solvent and a freezing procedure for extracting phase separation. A 7 mL sample volume adjusted to pH 5 was extracted with a drop of 35 μL of octanoic acid (0.5%v/v). The emulsification was initiated by shaking for 10 s followed by centrifugation for 5 min. The floating drops containing RhB were solidified in an ice bath, separated from the solution, defrosted, and dropped on the paper platform for DDIC analysis. The limit of detection (LOD) and limit of quantification (LOQ) were 1.8 μg L−1 and 6.0 μg L−1, respectively. The linear range was 10 - 40 μg L−1 (R2 = 0.997). The method was applied to determine RhB in beverage, candy, jelly, and chili sauce samples. The relative recovery percentages (RR%) between 73% and 113% were achieved.

The electrochemical degradation of tetraethylrhodamine, commonly known as Rhodamine B (RhB) in acidic aqueous solutions, was examined utilizing a platinum grid anode and a stainless steel cathode. This dye is a substance used to impart color to cotton, silk paper, bamboo, weed, leather, and other materials as well as to prepare carbon paper, ball pen, stamp pad inks, paintings, etc. In case of being swallowed by humans and animals, this chemical compound causes an irritation to the skin, eyes, gastrointestinal and respiratory tract, in addition to phototoxic and photoallergic responses. Experimental evidence of carcinogenicity, reproductive and developmental toxicity, neurotoxicity, and chronic toxicity in people and animals has been established. The effects of various experimental parameters on the RhB dye degradation were investigated. The optimum conditions are: a current of 100 mA, Fe(II) = 10 mg/L, and Na2SO4 = 10 mg/L. All the experiments were carried out at pH = 2.5. The % removal = 98.75 after 120 min. The combination of electro-Fenton and ultrasonic irradiation with a low frequency (sono-electro-Fenton process) was also studied. Sonoelectrochemical treatment of RhB-contaminated water yielded a significant, considerable percentage of 99% after 90 min at a current of 100 mA. [ABSTRACT FROM AUTHOR]

In this study, sludge-derived Fenton-like catalysts, namely potentially low cost, were successfully synthesized through a unique and original method, which was used to oxidative degradate Rhodamine B (RhB) as heterogeneous Fenton-like Fe/C catalysts. Two types of sludge sources were used as sludge-derived support carbon: paper mill sludge and municipal wastewater treatment sludge. This unique preparation method converted pyrolyzed sludge into a porous carbon-based carrier material by chemical activation and then used an iron loading impregnation method to synthesize the Fenton-like Fe/C catalyst. The prepared two types of catalysts including paper mill sludge-derived char-supported iron catalyst and municipal sewage sludge-derived char-supported iron catalyst were characterized in terms of Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and N2-adsorption/desorption. Compared with sludge-derived Fe/C catalyst without activation, both the PMSC-Fe and the MSSC-Fe catalyst exhibited much better catalytic performance in degrading RhB. Both PMSC-Fe and MSSC-Fe exhibited excellent catalytic stability and almost seldom Fe-ion leaching. A correlation could be found between surface area and RhB degradation, suggesting that surface area of the catalyst is an important factor for the catalytic performance. Two different sources of sludge also showed discrepancy in catalytic performance of RhB degradation, which is perhaps due to the different properties of the initial sewage sludge. The catalyst of PMSC-Fe and MSSC-Fe both has an excellent long-term stability. Possible degradation mechanism of RhB induced by sludge-derived Fe-C/H2O2 system is proposed. [ABSTRACT FROM AUTHOR]

In this work, a novel free‐standing three‐dimensional MoS2/rGO/Cu2O ternary composite grown on etched carbon paper is successfully synthesized by simple hydrothermal method and demonstrated for very fast photocatalytic degradation of methylene blue (MB), rhodamine B (RhB) and binary mixture MB‐RhB under natural sunlight irradiation. Interestingly, the ternary film exhibits fast dyes degradation of ∼98 % within 45 min of irradiation indicating its excellent photocatalytic activity owing to efficient absorption in broad range of spectrum and the combined synergistic effects of the nanostructures. In addition, the stable photocatalyst film is reused six times without any major loss in efficiency thus making it suitable for real time applications for sustainable environment. The as‐prepared free‐standing, reusable and stable film demonstrates a wide potential in environmental monitoring applications such as removal of organic pollutants and wastewater treatment. [ABSTRACT FROM AUTHOR]

A novel colorimetric-fluorescent dual-mode sensing sensor JT5 was successfully synthesized, and exhibited red fluorescence enhancement effect and red colorimetric sensing, and excellent applicability through solid-state fluorescent strips and biological imaging experiments on zebrafish to highly sensitive monitoring Sn4+ ions. [Display omitted] • A novel and effective rhdamine B-based sensor JT5 successful development. • JT5 can serve as a fluorescent and colorimetric on-off sensor for Sn4+. • The sensor JT5 was successfully studied using fluorescence and colorimetric of the test strips. • Biomaging experiments for the sensor JT5 were conducted on zebrafish using a confocal microscope. A novel colorimetric-fluorescent dual-mode chemosensor (JT5) based on rhodamine B has been produced for monitoring Sn4+ in the DMSO/H 2 O (4:1, v/v) medium. It has high sensitivity, a low detection limit, a short response time (1 s) and high stability, and can still be maintained after two weeks with the red dual fluorescence/ colorimetric response. Enhancement of red fluorescence (591 nm) and red colorimetric (567 nm) response of JT5 by Sn4+ addition. The electrostatic potential of the sensor JT5 molecule was simulated to speculate on the sensing mechanism, and the IR, mass spectrometry and 1H NMR titration were utilized to further demonstrate that JT5 was coordinated to Sn4+ with a 1:1 type, the rhodamine spironolactam ring of JT5 opens up to form a penta-membered ring with Sn4+, meanwhile, its system may have chelation enhanced fluorescence (CHEF) effect. In addition, theoretical calculations were carried out to give the energy gaps of JT5 and [ JT5 + Sn4+] as well as to simulate the electronic properties of the maximal absorption peaks. Notably, the sensor JT5 was successfully applied to monitoring Sn4+ in zebrafish, and the JT5 -loaded filter paper provided a solid-state platform for detecting Sn4+ by both naked eye and fluorescent methods. In summary, this work contributes to monitoring Sn4+ in organisms and solid-state materials and promotes understanding of Sn4+ functions in biological systems, environments, and solid-state materials. [ABSTRACT FROM AUTHOR]

In this work, a new turn-on fluorescent probe 1 for Hg2+ ions detection based on rhodamine B spirolactam was reported. Among tested metal ions, probe 1 shows high selectivity towards Hg2+ in the the mixture solution of methanol and 0.02 M HEPES buffer (V/V = 9:1, pH = 7.2). No absorption and emission band of probe 1 was observed in the range from 450 to 700 nm. While only addition of Hg2+ to probe 1 could lead to appearance of a new absorption band centered at 553 nm and a fluorescence emission band around 577 nm upon excitation at 520 nm. Moreover, it exhibits excellent linear relationship (R2 = 0.9993) between fluorescence intensity at 577 nm and the concentration of Hg2+ from 1.6 to 32 μM. The sensing mechanism was proven to be spirolactam ring open induced by Hg2+ through 1H NMR, MS, absorption and fluorescence spectra. In addition, probe 1 could detect Hg2+ in real water samples and on filter paper, which demonstrates its application in environment science. [ABSTRACT FROM AUTHOR]

This study focuses on the removal of organic dyes, such as Malachite Green (MG) and Rhodamine-B (Rh-B) from an aqueous solution with the help of a novel adsorbent (activated carbon) with magnetic property prepared by used disposal paper cups (AC@PC) at 500°C. The synthesized AC@PC adsorbent was characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and point of zero charge (pHZPC). Adsorption of MG and Rh-B onto the AC@PC adsorbent from aqueous solution was investigated systematically. Langmuir, Freundlich and Temkin isotherms were also studied, however, it has been observed that Langmuir isotherm model was best fitted for both the dyes, which describe the adsorption behaviour at equilibrium. Pseudo-first and pseudo-second order kinetic model describe the rate of adsorption. Kinetic study explained that the process of adsorption followed the pseudo-second order model. Thermodynamic parameters such as enthalpy (ΔH°), entropy (ΔS°) and Gibb’s free energy (ΔG°) were also studied and revealed that the adsorption of MG was endothermic, whereas adsorption of Rh-B was exothermic onto the AC@PC. The prepared adsorbent shows potentially high adsorption properties for both the dyes. [ABSTRACT FROM AUTHOR]

Two Schiff bases based on triphenylamine and phenothiazine, namely DTPA-SB and DPTZ-SB, respectively, were synthesized via facile organic transformations. The mixing of these two molecules with rhodamine B dye (Rh-B) resulted in efficient white light generation in the solution state as well as in the ionic liquid medium of [Bmim][Cl] with the Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.35) and (0.34, 0.35), respectively. Notably, the generation of white light in the ionic liquid medium has been reported for the first time. Several mechanistic studies, namely fluorescence titration, spectral overlap, Förster distance calculation and DFT studies, established that the mechanism of WLE is Förster resonance energy transfer with simultaneous emission. On a parallel note, DTPA-SB showed an excellent fluorescence sensing response towards 30% H2O2 with a remarkable limit of detection (LOD) of 8.4 × 10−7 M, while DPTZ-SB exhibited a slight decrease in the emission intensity with a LOD of 1.96 × 10−7 M. Both DTPA-SB and DPTZ-SB were specifically selective for 30% H2O2 without interference from fifteen other chemical species. Since DTPA-SB exhibited significant response towards hydrogen peroxide detection, a paper-based fluorescent sensor device was fabricated by embedding DTPA-SB on the filter paper with a LOD of 2.3 × 10−9 M. Additionally, a smartphone color-scanning app was tuned with the paper-based sensors to perform scanometric tests. A paper-based device for hydrogen peroxide sensing by applying a simple fluorescent Schiff base is reported herein for the first time. [ABSTRACT FROM AUTHOR]

• We introduce a colorimetric and SERS sensor for the dual-mode detection of H 2 S. • A simple and facile H 2 S assay was prepared by dropping of Ag nanoplate solution on paper. • We utilized the parameter b of CIE L*a*b color model for the quantitative color analysis. • The analytical performance of H 2 S sensing paper for dual-mode detection was evaluated. • This paper assay can detect endogenous H 2 S in live LNCaP cells under shorter incubation times. We report a simple and facile paper assay based on silver nanoplates (Ag NPls) for the colorimetric and surface-enhanced Raman scattering (SERS) dual-mode detection of hydrogen sulfide (H 2 S) gas released from live cancer cells. Ag NPls were prepared via seed-mediated growth and dropped on detection zones within the poly(dimethylsiloxane)-patterned paper substrate. The blue-colored Ag NPls on the paper react with H 2 S to form brown-colored silver sulfide, which simultaneously decreases SERS activity of Ag NPls. We quantitatively analyzed the color and Raman signal intensity changes in Ag NPl-coated detection zone on the paper, using the parameter b of L*a*b color space and Raman peak at 1356 cm−1 of Rhodamine B, respectively. As a result, our Ag NPl-coated H 2 S dual-sensing paper assay showed a good sensitivity with a linear range of 1.64–16.4 μM H 2 S and a detection limit of 520 nM for colorimetric detection. And, it also represented a high sensitivity with a linear range of 82–330 nM H 2 S for SERS detection. In addition, it possessed high selectivity, excellent reproducibility, and high stability over 1 month. Using this Ag NPl-coated H 2 S dual sensing paper, we successfully measured the H 2 S concentration in live prostate cancer cells at different incubation times and cell numbers. Therefore, the Ag NPl-coated paper assay can be utilized as a facile and effective tool for the dual-mode colorimetric and SERS detection of free H 2 S gas within live cells without complicated sample processing or labor-intensive bioanalytical methods. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Continuous waste discharge into natural water resources in many countries is a severe global issue, and seeking an effective solution is a researcher’s concern. Herein, toilet paper waste was a low-cost precursor for preparing carbon nanoparticles (TPCNPs). The characterization of TPCNPs revealed a 30 nm to 50 nm particle size, a 264 m2 g−1 surface area, and a cubical graphite lattice XRD pattern. The TPCNPs were tested for removing malachite green (MG), indigo carmine (IC), rhodamine B (RB), and methylene blue (MB) dyes from water. The solution parameters were examined for the sorption process, and a pH of 5.0 suited the MB removal, while a pH of 6.0 was suitable for MG, IC, and RB. The effect of concentration investigation showed an adsorption capacity of 110.9, 64.8, 73.5, and 98 mg g−1 for MG, IC, RB, and MB, respectively. The sorption of the four dyes fitted the Langmuir isotherm model; it was exothermic and spontaneous. The water remediation was tested using groundwater and seawater samples (GW and SW) spiked with pollutants. It is worth mentioning that one treatment sufficed for the remediation of GW and SW contaminated by 5 mg L−1 concentration, while a double treatment was required for 10 mg L−1 pollution in both samples.

Conventional indicator paper is disposable after use and requires a large amount of target solution. Herein, recyclable upconversion fluorescence indicator papers consisting of upconversion nanorods and plasmonic nanostructures are fabricated by electrospinning. This recyclable indicator paper exhibits good flexibility and superhydrophobicity with enhanced upconversion fluorescence. Rhodamine B (RhB) is selected as the target solution because it is prohibited as a food additive but often occurs in food, and conventional detection methods usually need a large volume of solution (>1 mL) to refine to higher concentrations because of the low detection sensitivity. Significantly different from the traditional detection system, this upconversion fluorescence fibrous indicator paper can detect RhB as low as 0.01 ppm, which is superior to most reported detection limits for fluorescence sensors. Moreover, this indicator paper can detect a single droplet (≈10 µL) of RhB without needing a large amount of solution. After detection, the target solution is easily removed for excellent recyclability, which is another advantage over the traditional detection system. [ABSTRACT FROM AUTHOR]

The crystal violet (CV) staining technique represents a prevalent approach for the development of latent fingerprints, especially on adhesive tape surfaces. Nevertheless, the technique necessitates intricate formulations to augment its performance. In this investigation, an optimized CV staining protocol was developed, characterized by the absence of residual dye on the target substrates and the capability of facilitating fingerprint visualization under ambient light conditions. Four donors, comprising two males and two females, deposited natural fingerprints on various substrates, including glass microscope slides, aluminum foil, and 115 g glossy coated paper, without any specific guidelines. Fingerprints developed using cyanoacrylate fuming served as benchmarks and were contrasted with those generated through alternative methods: CV, ardrox, rhodamine 6G, powdering, and the optimized CV staining protocol. The fingerprint development experiment was replicated at seven distinct time intervals, encompassing 1 day, 1 week, 1, 3, 6, 9, and 12 months, resulting in a dataset of 420 fingerprints. The evaluation of fingerprint identifiability employed a scoring system established by the Home Office Centre for Applied Science and Technology. The results indicated that the optimized CV staining technique demonstrated superior performance, boasting a 92.9% rate of identifiable fingerprint development in contrast to other employed methodologies. Consequently, this optimized CV staining approach is recommended as an efficient, rapid, and straightforward critical dyeing method, applicable to a wide array of substrates in forensic investigations. [ABSTRACT FROM AUTHOR]

Paper‐based surface‐enhanced Raman scattering (SERS) substrates have gained growing interest as an eco‐friendly and low‐cost tool for chemical and biosensing. However, paper‐based SERS substrates often suffer relatively low signal spatial homogeneity because of their nonuniform hot‐spot distribution. In this paper, a nanofibrillated cellulose paper (nanopaper) based SERS multiwell plate is developed for trace chemical detection with high sensitivity and high signal homogeneity. The SERS plate is fabricated from ultrasmooth (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl‐oxidized NFC paper (TO‐nanopaper) through wax‐printing‐based multiwell patterning followed by silver nanoparticle (AgNP) growth based on a successive ionic layer adsorption and reaction (SILAR) process. Taking advantage of the abundance of carboxyl groups on the TO‐nanopaper, uniformly distributed and densely arranged AgNPs are successfully synthesized through the SILAR process on the NFC multiwell surface under ambient conditions. The SERS performance of the device is evaluated for testing two Raman marker chemicals, rhodamine B and 2‐naphthalenethiol, and picomolar detection limit and high Raman enhancement factor (up to 1.46 × 109) are achieved. The Raman signal mapping results show superior signal spatial homogeneity of the device with low variations (≤11%). The nanopaper‐based SERS device represents a promising SERS platform for chemical and biomolecule detections with high sensitivity and high repeatability. [ABSTRACT FROM AUTHOR]

In this work, the Ag3PO4 modified with graphene quantum dots composites (GQDs-Ag3PO4) were synthesized via a facile precipitation method to further improve the photocatalytic performance of Ag3PO4. Interestingly, these GQDs-Ag3PO4 exhibited improved visible light photocatalytic performance for the degradation of rhodamine B than pure Ag3PO4. The composite with GQDs weight percentage of 0.48 showed the most excellent performance, which was completely almost 11.25 times than that of pure Ag3PO4. Furthermore, this composite also showed excellent photocatalytic performance for the photodegradation of para-chlorophenol, levofloxacin and negatively charged aromatic dye methyl orange. The remarkable enhancement of photocatalytic performance should be attributed to the larger surface area, the enhanced light absorption property and the effective suppression of electron-hole recombination. [ABSTRACT FROM AUTHOR]

Since the abuse of antibiotic oxytetracycline (OTC) poses a serious threat to the environment and human health, it is of great importance to develop sensitive fluorescent probes for its rapid and in situ detection. Herein, a dual fluorescence response probe based on an aluminum-incorporated metal–organic framework (MOF) was presented for OTC assay. Unlike internal references that demonstrate an independent and stable fluorescence signal intensity in traditional dual-emissive probes, the fluorescence of rhodamine B immobilized in a prepared probe was gradually enhanced at a 585 nm emission wavelength with increasing concentrations of OTC under 405 nm excitation, while OTC also experienced an obvious fluorescence enhancement at a 521 nm emission wavelength due to a molecular conformation transition from the twisted to the extended state, realizing a molecular conformational transition-induced dual fluorescence enhancement for OTC detection under a single excitation wavelength. In addition to the mechanism exploration and double linear range for OTC quantification with nM level detection limits in solution, a paper-based portable test strip was successfully fabricated by loading the probe on glass fiber filter paper with an obvious fluorescence color change from orange to yellow upon increasing the addition of OTC. We expect that the proposed probe in this work would provide an example for the design of organic fluorophore-based sensors exhibiting multiple fluorescence responses under a single excitation. [ABSTRACT FROM AUTHOR]

The demand for encoded surfaces has increased significantly over the past decade driven by the rapid digitalization of the world. Surface‐enhanced Raman scattering (SERS) offers unique capabilities in generation of encoded surfaces. The challenge is the limited versatility of SERS‐based encoding systems in terms of the applicable surfaces. This study addresses this challenge by using a temporary tattoo approach together with simplified fabrication of SERS‐active patterns by ink‐jet printing of a particle‐free reactive silver ink. Plasmonic silver nanostructures form on the tattoo paper upon ink‐jet printing and a brief thermal annealing. The SERS activity is sufficient to detect taggant molecules of rhodamine 6G, methylene blue, and rhodamine B with a nanomolar level sensitivity. Raman‐active taggants can be incorporated into the ink, for drop‐on‐demand patterning of multiple molecules in 1D and 2D barcode geometries. The SERS barcodes can be effectively transferred to a range of different substrates retaining high plasmonic activity and geometric integrity. The presented approach decouples the SERS‐active pattern preparation from the final substrate and greatly improves the versatility of the barcodes. [ABSTRACT FROM AUTHOR]

Many works include the use of nylon membranes to separate the solid particles of photocatalysts from the photocatalytic reactors, before using spectrophotometers to evaluate the catalysts’ performance in the photocatalytic degradation of many pollutants. This might lead to significant errors due to the adsorption of some pollutants within the structure of the membranes during the filtration process used to separate the solid particles of the photocatalysts to get a clear filtrate. This, consequently, leads to incorrect calculations, which in turn are translated into false high photocatalytic efficiencies of the used catalysts. In this work, the authors study the interaction between nylon membrane filters and five different model compounds—phenol red, methylene blue, rhodamine B, rhodamine 6G, and phenol. The study reveals a significant interaction between the nylon membranes and both rhodamine B and phenol red.

[Display omitted] • Recyclable silver immobilized chitosan/carboxy methyl chitosan macromolecules as visible light-responsive photocatalyst. • Structural tailoring morphological studies was scrutinized using advanced techniques. • Highly efficient photocatalytic degradation of methyl orange (MO) and rhodamine B (RB) dyes from wastewater. • Optimization of degradation using response surface methodology (RSM). This study explores the potential of modified chitosan (CH) resulting from carboxy methyl (CM) group substitution in the chitosan skeleton, producing carboxy methyl chitosan (CMCH). Silver (Ag) was loaded to chitosan and modified chitosan (carboxy methyl substituted chitosan) supported on cellulose filter paper (FP) to tailor organic–inorganic macromolecule composites "Ag-Chi/CFP and Ag-CMCH/CFP" further applied as substantial composite for the reductive removal of methyl orange (MO) and rhodamine B (RB) dyes from wastewater. The synthesized catalyst was characterized via FTIR, 1H NMR, XRD, and SEM analysis. The degree of substitution was also measured, which was approximately 0.85. The reductive elimination efficiency of Ag-CMCH/CFP and Ag-Chi/CFP for MO dye was 95.31% and 88.85 %. In comparison, the elimination of RB was 98.28 and 94.04 %, respectively, in 16 min time, 0.6 mM Ag concentration, 40 mg/L, dye concentration and 0.3 M NaBH 4 concentration. The synthesized catalysts were recycled three times. The degradation of MO and RB dyes using Ag-CMCH/CFP and Ag-Chi/CFP catalysts can be described by the first-order kinetic model. The determination coefficients (R2) and rate constants (k) values for MO degradation were found to be 0.9934 and 0.1736 s−1 for Ag-CMCH/CFP, and 0.9242 and 0.1001 s−1 for Ag-Chi/CFP, respectively. Similarly, for RB degradation, the R2 values were 0.9866 for Ag-CMCH/CFP and 0.9803 for Ag-Chi/CFP, with corresponding k values of 0.219 s−1 and 0.1548 s−1, respectively. The degradation process was optimized using response surface methodology (RSM) to determine the optimal conditions for maximum dye removal efficiency. The RSM models were statistically significant, as validated by ANOVA and correlation coefficient values. The F values of MO and RB models are significant as they have 2450.15 and 21999.37, respectively. The P value for both was <0.0001. [ABSTRACT FROM AUTHOR]

Magnetic chicken bone-based biochar (MCBB) was successfully prepared and efficiently adsorbed rhodamine-B (RB) dye and tetracycline (TC) in multi-component systems. The magnetisation value, surface area, and pHpzc of the MCBB were found to be 66.5 emu/g, 328 m2/g, and 8.3, respectively. RB has higher saturation capacity (96.5 mg/g) and occupies more active sites on MCBB, thus limiting the sorption of TC with lower saturation capacity (63.3 mg/g). Langmuir isotherm suitably describes the sorption process in a single-component system; however, the multi-component system was well fitted to the Sheindorf-Rebhun-Sheintuch model. The selectivity factor values confirmed that MCBB had higher adsorption affinity toward RB than TC. The intraparticle diffusion model played a significant role in the sorption process. The MCBB can be easily desorbed with base-spiked H2O and reused without loss in stability or structural integrity. [ABSTRACT FROM AUTHOR]