Search Results (132)

The green synthesis of zinc oxide (ZnO) nanoparticles using plant biomass offers a sustainable approach for developing photocatalytic materials for water treatment. In this study, ZnO nanoparticles were biosynthesized using aqueous extracts of Eichhornia crassipes from the Medio Atrato region, Chocó, Colombia, at 1%, 2%, and 4% (w/v). The materials were characterized by FTIR, UV-Vis, XRD, and SEM–EDX. All samples exhibited the hexagonal wurtzite structure of ZnO without detectable secondary crystalline phases. Average crystallite sizes were 38.66, 38.16, and 31.52 nm for EC-1%, EC-2%, and EC-4%, respectively, decreasing with increasing extract concentration. Photocatalytic activity was evaluated under UV irradiation using six organic dyes: amido black 10B, eosin yellow, methylene blue, methyl orange, methyl red, and rhodamine B. Performance depended on both pollutant type and extract concentration. EC-2% showed the most consistent overall performance, achieving 87% degradation of amido black 10B, 92% of methyl orange, 81% of methyl red, and 93% of rhodamine B. Eosin yellow reached approximately 97% removal at 90 min, while EC-4% achieved 95% methylene blue degradation after 180 min. EC-2% also removed approximately 56.78% of chlorpyrifos ethyl after 180 min. Overall, E. crassipes-mediated ZnO nanoparticles demonstrate promising photocatalytic activity toward diverse organic pollutants and provide a potential route for valorizing invasive aquatic biomass. Full article

While silver halides (AgX) are promising visible-light photocatalysts for water remediation, their practical deployment is severely hindered by intrinsic photocorrosion, rapid charge recombination, and macroscopic recovery challenges. Here, we demonstrate a monolithic AgX/biomass carbon aerogel composite platform, constructed by anchoring AgX nanocrystals in situ onto a 3D hierarchical carbon skeleton. The carbon network not only suppresses nanoparticle aggregation but also plays contrasting optical roles: amplifying the intrinsic visible-light absorption of AgBr while endowing the otherwise UV-confined AgCl with substantial visible-light response. Consequently, the optimal 30 wt% AgBr/CA composite achieves a 95.68% methylene blue degradation efficiency within 60 min—outperforming pristine AgBr by 2.6-fold—while establishing robust activity against two additional, structurally distinct pollutants: rhodamine B and the colorless antibiotic ciprofloxacin. Notably, the free-standing monolith retains exceptional activity over six consecutive cycles. Mechanistic investigations reveal that the carbon aerogel functions as an electron-accepting reservoir, which accelerates interfacial charge separation and steers electron flow toward superoxide radical generation. Notably, XRD and XPS analyses confirm that no detectable metallic Ag⁰ is present in the as-prepared composites. This work establishes a sustainable and scalable architectural paradigm for designing highly efficient, stable, and easily recyclable photocatalytic systems. Full article

Phosphogypsum (PG) is a major solid by-product generated during wet-process phosphoric acid production. Its stockpiling poses significant environmental risks due to the potential leaching of harmful substances. Therefore, conversion of PG into high-value-added products is urgent. In this work, nano-calcium carbonate (Nano-CaCO₃) was synthesized from PG via a phase-transfer precipitation method. The surface of the as-prepared product was then modified for Hg²⁺ detection. Initially, the nanoparticle surface was functionalized with (3-aminopropyl)triethoxysilane (APTES), followed by grafting with a synthesized rhodamine B-based derivative (RhoB-NCS). The acquired product was denoted as CaCO₃@RhoB-NCS. Physical characterization demonstrated its successful fabrication. The product is an effective sensor for Hg²⁺ detection, exhibiting enhanced fluorescence emission at 600 nm with a detection limit as low as 1.0 × 10⁻⁶ M. Moreover, the CaCO₃@RhoB-NCS was used as a filler for Hg²⁺ test paper. This work demonstrates a promising approach for valorizing solid waste into high-value-added product. Full article

Chili products are vulnerable to the addition of unauthorized substances, including Sudan dyes, Rhodamine B, Basic Orange 2, poppy-derived materials and improperly used processing chemicals. Their analysis is complicated by the high contents of lipids, carotenoids, capsaicinoids and other co-extracted matrix components in chili powder, chili oil, chili sauce and composite seasonings. This review critically evaluates conventional and emerging sample-preparation strategies, including solid-phase extraction; the quick, easy, cheap, effective, rugged and safe (QuEChERS) procedure; deep eutectic solvent (DES)-assisted extraction; enhanced matrix removal for lipids (EMR-Lipid); and molecularly imprinted sorbents. Laboratory methods based on high-performance liquid chromatography (HPLC), liquid chromatography–tandem mass spectrometry (LC–MS/MS) and gas chromatography–mass spectrometry (GC–MS) are compared with enzyme-linked immunosorbent assay (ELISA), surface-enhanced Raman spectroscopy (SERS), electrochemical sensors, miniature mass spectrometry and artificial intelligence-assisted hyperspectral imaging (AI–HSI). The comparison considers representative limits of detection and quantification, recovery, precision, sample-preparation burden, cost, portability, validation status and regulatory role. LC–MS/MS remains the preferred confirmatory platform for targeted multi-residue analysis, whereas rapid and portable methods are more appropriate for screening and sample triage. A three-tier workflow linking rapid screening, laboratory confirmation, and emerging-risk identification and traceability is proposed. Future priorities include standardized chili reference materials, open AI training and validation datasets, greener DES-based extraction and interlaboratory validation of field-deployable methods. Full article

Heterogeneous photocatalysis has attracted attention as an effective method for the degradation of a wide range of organic contaminants. Despite the growing interest in ceria- and manganese oxide-based photocatalysts, CeO₂/Na-birnessite heterostructures remain largely unexplored. Therefore, CeO₂/Na-birnessite composite materials were synthesized by a hydrothermal method and investigated for photocatalytic water treatment. XRD and WPPF analyses confirmed the coexistence of fluorite-type CeO₂ and layered Na-birnessite, while an additional hausmannite phase was detected in the Mn-rich samples. SEM, TEM and EDS analyses revealed close spatial contact between ceria nanoparticles and layered birnessite structures. The mixed samples exhibited higher specific surface areas than the pure oxides, reaching up to 121.7 m² g⁻¹ for the 50Mn:50Ce composition. UV–Vis DRS showed enhanced visible-light absorption with increasing manganese content. Photocatalytic activity was evaluated through Rhodamine B degradation under UV irradiation at solution pH values below and above the point of zero charge (pH_pzc = 6.46) determined for the 50Mn:50Ce sample. Significantly higher photocatalytic activity was observed at pH 7.5, where the 50Mn:50Ce sample achieved more than 90% Rhodamine B degradation after only 20 min of irradiation. These results suggest that photocatalytic performance depends on the combined effect of high specific surface area and surface charge control. Full article

Wastewater contamination with synthetic organic dyes is a significant environmental challenge. Zinc oxide (ZnO) has attracted considerable attention as a non-toxic, multifunctional material for electronics, optics, piezoelectric devices, and photocatalysis, where its performance is strongly governed by morphology. In this work, we investigate the effect of hexamethylenetetramine (HMTA) on the formation and photocatalytic behavior of ZnO nanostructures synthesized from different zinc precursors, namely zinc acetate and zinc nitrate, via a one-step sol–gel process at low temperature without any post-treatment. All samples crystallize in the hexagonal wurtzite phase without detectable impurities, and the incorporation of HMTA leads to smaller, more uniform rod- and flake-like nanostructures. Although ZnO derived from zinc acetate without HMTA exhibits the highest specific surface area, ZnO synthesized in the presence of HMTA shows more favorable crystallinity, morphology, and pore connectivity, which together enhance charge separation and reactive oxygen species generation. As a result, ZnO samples synthesized with HMTA exhibit improved photocatalytic degradation of rhodamine B under UV irradiation. Full article

Several strategies can be employed for the identification of novel microbial lipases. Despite the increasing importance of metagenomics in bioprospecting, significant limitations in the expression of recombinant proteins, and lipases in particular, remain. Culture-based bioprospecting approaches are, therefore, still valuable. In this work, a collection of bacterial isolates, mainly of marine origin, was screened for lipase activity through a culture-based approach. Screening for lipolytic bacteria was performed in solid media containing olive oil emulsions and rhodamine B. Positive isolates were subsequently grown in liquid media, to confirm lipase production. Significant hydrolytic activity towards the triglyceride substrates tributyrin and triolein could be observed with the biomass produced, although no lipase activity could be detected in the culture supernatants. Six isolates presenting high activity were characterized as whole-cell biocatalysts, and all were found to be active at temperatures ranging between 25 and 65 °C, and at pH values between 6 and 10.5. Genomic analyses of two of these Gram-negative lipase-producing isolates revealed the presence of several hypothetical genes encoding for lipolytic enzymes, including outer cell-bound enzymes, predicted through the application of machine-learning tools. These natural isolates, containing cell-associated lipases, may therefore be of special interest for application as whole-cell biocatalysts. Full article

Fifty-five batik textiles produced along coastal Java in the late 19th to early 20th century were analysed to study the red dyes and the cotton fabrics. Surface-Enhanced Raman Spectroscopy (SERS) classified the dyes into six groups and identified 70% of the samples as Morinda. High-Performance Liquid Chromatography coupled with a diode array detector and tandem Mass Spectrometry (HPLC-DAD-MS/MS) confirmed the SERS results and identified synthetic dyes in the remaining samples, which were used either alone or in mixtures with Morinda or indigo. Synthetic alizarin (C.I. 58000, Mordant Red 11) was the most frequently detected synthetic dye. Auramine O (C.I. 41000, Basic Yellow 2), fuchsin (C.I. 42510, Basic Violet 14), and rhodamine B (C.I. 45170, Basic Violet 10) were occasionally detected. The results also highlighted two possible types of Morinda and two variations of synthetic alizarin. The shades obtained from mixtures of natural and synthetic dyes were visually indistinguishable from those obtained with pure natural or synthetic dye, as confirmed by colourimetry. The variety of dyes and cotton fabrics shared across batik producers makes it challenging to attribute unsigned batiks to specific workshops. Nevertheless, this study demonstrated that synthetic dye uptake during this period was limited and experimental, with natural Morinda remaining the preferred choice despite the availability of European synthetic alternatives. Full article

Cost-effective, fluorescence-based biodiagnostic devices have the potential to expand point-of-care (POC) testing in resource-limited settings, thereby creating new opportunities for accessible and decentralised diagnostics. The objective of this study is to investigate the performance of a newly designed and simplified system that uses several cost-effective sensors for use in a fluorescence-based biodiagnostic setup. A collecting setup that includes an elliptical mirror to focus emitted fluorescence onto the semiconductor sensors was designed for an intensity-based readout. The readout was realised by various photodiodes, photoresistors, phototransistors and one multi-pixel photon counter (MPPC). Over a range of fluorophore concentrations using serial dilutions of Rhodamine B (RhB), the limit of detection (LOD) and limit of quantification (LOQ) at system level were evaluated. With the exception of the photodiodes, the system demonstrated promising performance with all sensors. The system using the photoresistors achieved the lowest LOD but showed limited repeatability, while the system using the MPPC and phototransistors exhibited high repeatability. A proof-of-concept demonstrated the feasibility of a photoresistor-based configuration by using a sandwich immunoassay for the detection of the antigen Human Epidermal growth factor Receptor 2 (HER2) (100 nM). While this study has not yet encompassed the full spectrum of clinically relevant concentrations, it has yielded valuable insights to enable further enhancements, without the necessity for highly specialised or costly equipment. The limitations and necessary improvements for further developments are discussed. Full article

Fluorescent dyes are commonly used as tracers in hydrological investigations to quantify transport pathways, residence times, mixing behavior, and connectivity in surface water, groundwater, and coastal systems. Despite their long history of application, the ecological implications of deliberate dye releases are not well understood. This review synthesizes current knowledge on the physico-chemical characteristics, environmental behavior, and ecotoxicological effects of major dye classes, with emphasis on rhodamines, fluorescein derivatives, and sulfonated xanthene dyes commonly used in water tracing studies. Toxicity data for algae, cyanobacteria, invertebrates, and fish show large inter-specific variability. Some dyes, particularly rhodamine B and eosin Y, show acute or sub-lethal effects at concentrations detected during poorly controlled applications. By contrast, dyes with high polarity and extensive sulfonation (e.g., rhodamine WT, sulforhodamine B, pyranine, and fluorescein) show consistently low toxicity and minimal bioaccumulation potential. Environmental fate processes, including photolysis, sorption, and transformation into potentially more reactive products, influence exposure dynamics, especially in clear, shallow, or slow-moving systems. This review also evaluates regulatory frameworks and operational guidance for safe use, identifies gaps in toxicological and fate data, and proposes recommendations for minimizing environmental impact through dye selection, mass optimization, injection design, and monitoring. The findings support the continued use of fluorescent dyes but highlight the need for more systematic assessment of transformation products, chronic and sub-lethal responses, and cumulative exposure in sensitive environments. Full article

Fluorescent carbon dots (CDs) were efficiently synthesized by a one-step microwave-assisted method using diphenylamine as a carbon precursor. The obtained CDs exhibit high stability and strong water solubility. Under UV irradiation, these CDs could emit bright green photoluminescence. These synthesized CDs have an average diameter of 1.8 nm (±0.46) and quantum yield (QY) as high as 44.69% using rhodamine-B as a reference. The CDs’ intensity can be quantitatively quenched by Hg²⁺ and Fe³⁺ ions with high sensitivity and low LOD about 9.58 nM and 22.27 nM, respectively, indicating that the CDs sensors can be potentially applied for Hg²⁺ and Fe³⁺ detection in aqueous solutions. Full article

Most reported fluorescent Al³⁺ probes rely on fluorescence signal enhancement or quenching. Since the change in fluorescence intensity is the sole detection signal, various factors such as instrumental efficiency, environmental conditions, and probe concentration can interfere with the signal output. In contrast, ratiometric probes, which utilize two emission bands for self-calibration, provide significant advantages by minimizing or eliminating these uncertainties. In this study, a naphthalimide-rhodamine based the transition between the cyclic and open-ring forms of rhodamine as an Al³⁺-selective ratiometric probe, in which chitosan was identified as an ideal bridge and biocompatibility. The design concept was that when the target metal ion was present, the fluorescence intensity of naphthalimide remained largely unchanged, serving as an internal standard. In contrast, rhodamine B was employed to label the target molecules, with its fluorescence intensity varying in accordance with the target concentration. A series of experiments were carried out to investigate the fluorometric properties of the grafted polymer P. The results demonstrated that P exhibited selective interaction with Al³⁺ among the various metals tested. Using the fluorescence intensity ratio (I_{603 nm}/I_{538 nm}) of P, a good linear relationship was achieved for Al³⁺ concentrations ranging from 1.0 to 35.0 μM with a detection limit of 0.33 μM was obtained. Meanwhile, we employed the standard addition method for the quantitative analysis and detection of Al³⁺ in commercially available bottled water and tap water, achieving an ideal recovery rate. Full article

We present the design, fabrication, and optical characterization of fully polymer-based high performance Fabry-Pérot microcavities for sensing and lasing applications. Two microcavity types (Cavity A and B) were realized using polymeric Distributed Bragg Reflector (DBR) films offering distinct spectral properties. Cavity A achieved a high quality factor (Q ≈ 2.15 × 10⁵), demonstrating excellent sensitivity for bulk refractive index sensing with an ultrahigh figure of merit of 5.89 × 10⁴ and a theoretical detection limit down 3.4 × 10⁻⁷ RIU. Cavity B was optimized for lasing applications. When filled with a Rhodamine B dye solution, it exhibited clear lasing action with a low threshold (1.83 μJ/mm²) and resonant peaks consistent with its free spectral range. These results highlight the potential of cost-effective polymeric cavities for disposable photonic sensor platforms and integrated biolaser devices. Full article

This paper introduces a novel Lateral Extraction Enhanced Desorption Electrospray Ionization (LEE-DESI) source. This source is specifically designed to tackle the crucial issue of electric field interference in dual-channel ambient ionization mass spectrometry (AIMS). By incorporating dual-channel spraying-based desorption and extraction into a 3D-printed chamber with optimized spatial parameters, the system effectively reduces cross-channel interference while boosting ionization efficiency. The desorption spray is responsible for desorbing analytes from untreated samples, and the extraction spray further ionizes more neutral droplets through charge transfer, which substantially enhances sensitivity. Compared with traditional DESI, the LEE-DESI source demonstrates improved detection limits, reproducibility, and operational simplicity, as validated using Rhodamine B, L-arginine, and Angiotensin I, as well as drug standards including methadone, ketamine, and fentanyl. This highlights its potential for high-throughput analysis of complex matrices in proteomics, metabolomics, and biomedical applications. Full article

Tribocatalysis is receiving more and more attention for its great potential in environmental remediation. In this study, a special tribocatalysis was explored as a powder-free catalytic technology for the degradation of organic dyes. Polytetrafluoroethylene (PTFE) and titanium (Ti) disks were first assembled as magnetic rotary disks and then driven to rotate through magnetic stirring in dye solutions in beakers with PTFE, Ti, and Al₂O₃ disks coated on bottoms separately. PTFE and Ti generated dynamic friction with the disks on the beaker bottoms in the course of magnetic stirring, from which some interesting dye degradations resulted. Among those dynamic frictions generated, 40 mg/L rhodamine b (RhB), 30 mg/L methyl orange (MO), and 20 mg/L methylene blue (MB) were effectively degraded by the one between PTFE and PTFE, the one between Ti and Ti, and the one between PTFE and Ti, respectively. Hydroxyl radicals and superoxide radicals were detected for two frictions, one between PTFE and PTFE and the other between Ti and Ti. It is proposed that Ti in friction increases the pressure in blocked areas through deformation and then catalyzes reactions under high pressure. Mechano-radicals are formed by PTFE through deformation, and are responsible for dye degradation. This work demonstrates a powder-free tribocatalysis for organic pollutant degradation and suggests an especially eco-friendly catalytic technology to wastewater treatment. Full article