Fluorescent starch-based hydrogel with cellulose nanofibrils and carbon dots for simultaneous adsorption and detection of Pb(II)

Pectin based Maillard reaction products: Formation mechanism and fluorescence characteristics

Pectin-based MR fluorescent product (PCD) was prepared using green-renewable pectin and l-lysine under the hydrothermal condition, which was characterized by bright yellow scaly powder. The chemical structural analysis showed that α-1,4-glucoside bonds linked active carbonyl compounds produced by demethoxylation and decarboxylation reactions in pectin, further react with l-lysine to form PCD with a moderate amount of π-conjugated structure, CN, CN, pyridine ring and pyrrole ring structure, causing yellow fluorescence in solid-state and stable blue fluorescence in liquid-state. Importantly, the steric hindrance and structural rigidity caused by pectin-like reticulated structure, more crystalline surfaces and structural complexity made PCD a good optical performance including covert apparent color, higher fluorescence quantum yield, less susceptibility to aggregated fluorescence quenching, excellent photostability, higher ion resistance, better solvent stability and wider pH application range than glucose-based MR product (GCD). This is favorable in the future for its potential application in anti-counterfeiting, fluorescence-responsive film preparation and bio-imaging.

Multifunctional natural starch-based hydrogels: Critical characteristics, formation mechanisms, various applications, future perspectives

With the growth of the global population and increasing concern for environmental issues, the development of sustainable and eco-friendly materials has become increasingly important. Starch, as a renewable resource, is one of the most abundant polysaccharides in nature, with the advantages of good biocompatibility, high biodegradability, and low cost. Starch-based hydrogels (SBHs) have attracted widespread attention due to their unique physical and chemical properties. This article provides a comprehensive review of the latest research progress in SBHs, discussing their main characteristics, formation mechanisms, diverse applications, and future development trends. First, it outlines the biocompatibility, degradability, water absorption and retention, environmental responsiveness, and mechanical strength of SBHs. Then, it elaborates in detail on the formation mechanisms of SBHs, including physical crosslinking (hydrogen bonding, electrostatic interactions, host-guest and coordination interactions), chemical crosslinking (such as initiators, heat, light, radiation, and click reactions), and synergistic effects. Subsequently, it analyzes the applications of SBHs in cutting-edge fields such as flexible sensors, medical dressings, drug delivery, tissue engineering, soil protection, wastewater treatment, and food packaging. Finally, it summarizes the challenges in current research and provides an outlook on future development trends, emphasizing the importance of further optimizing the performance of SBHs to meet broader industrial needs and environmental protection goals. This review not only provides a systematic theoretical framework for the study of SBHs but also charts a course for their innovative applications in the field of sustainable materials, playing a significant role in advancing the continuous development of this area.

Carboxymethyl cellulose and sodium alginate-enhanced hydrogel for carbon dots loading: A novel platform for pH sensing and sensitive detection of Al3+ and Ag. Int J Biol Macromol 2025;307:141955. [PMID: 40074127 DOI: 10.1016/j.ijbiomac.2025.141955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

To address the challenges associated with the storage and application of traditional carbon dot (CDs) solutions, this study introduces a cyan fluorescent carbon dot-based hydrogel (CDs-SCH). The hydrogel was synthesized by integrating cyan fluorescent CDs, derived from penicillamine and m-phenylenediamine, with carboxymethylcellulose (CMC) and sodium alginate (SA), which was then mixed with acrylamide (AM). The resulting CDs-SCH hydrogel was extensively characterized, focusing on its morphology, chemical structure, and fluorescence behavior. The fluorescence intensity of the hydrogel was enhanced by 3.23 times compared to the original CDs. The fluorescence response of the CDs-SCH hydrogel to pH variations was examined, demonstrating its capability to visually monitor the freshness of aquatic products such as fish and shrimp. Furthermore, Al3+ and Ag+ ions were found to significantly modulate the fluorescence, with Al3+ enhancing and Ag+ quenching the fluorescence, displaying reliable detection limits and linearity. The hydrogel's ability to detect glutathione (GSH) via Ag+ reduction to Ag was also explored. Additionally, the hydrogel exhibited stable Al3+ adsorption, with the process following pseudo-second-order kinetics and the Langmuir adsorption model. As a versatile and responsive material, the CDs-SCH hydrogel holds potential for applications in intelligent food packaging and environmental ion detection.

Cellulose as Source and Matrix for Fluorescent Chemo-Sensors

The review explores the pivotal role of cellulose in enhancing the sensing capabilities of fluorescent chemo-sensors, particularly carbon dots (CDs) and delineates cellulose's multifaceted contributions as both a precursor and stabilizing matrix, highlighting its structural adaptability across varied forms-hydrogels, aerogels, films-to bolster the stability, sensitivity, and selectivity of these sensors. Cellulose's structural versatility enables advanced functionalization, fostering a robust platform that amplifies the stability and functional efficiency of CDs across diverse sensing paradigms. The investigation encompasses utilization of cellulose as precursor for CDs, cellulose nanocrystals and matrix for the integration of CDs, elucidating their collective impact on advancing fluorescence-based detection technologies.

Development of an optode based on 2-amino-4-(4-nitrophenyl)diazenyl pyridine-3-ol and tri-n-octyl phosphine oxide for trace-level lead detection in complex samples

A new selective optode has been created for the ultra-sensitive detection of lead ions at trace levels. The membrane is created by incorporating tri-n-octylphosphine oxide (TOPO), 2-amino-4-(4-nitrophenyl)diazenyl pyridine-3-ol (ANPDP), and sodium tetraphenylborate (Na-TPB) into a matrix of plasticized poly(vinyl chloride) (PVC) and o-nitrophenyloctyl ether (o-NPOE). ANPDP serves as a chromophore in this design, while TOPO promotes the formation of a complex between lead ions (Pb2+) and ANPDP, resulting in a cooperative interaction. The composition of the optode was optimized to achieve maximum sensor performance. The sensor exhibits a linear dynamic range from 6.0 to 160 ng mL-1, with quantification and detection limits of 5.9 ng mL-1 and 1.8 ng mL-1, respectively. The membrane demonstrated rapid response times and long-term durability, with no detectable leaching of ANPDP. To ensure accurate total lead determination, Pb4+ ions were reduced to Pb2+ using 6.00 M HCl and freshly prepared 2.50% (w/v) sodium azide. The optode sensor exhibited superior specificity for Pb2+ ions, even when other ions that could potentially interfere were present. It could be effectively regenerated by treatment with 0.1 M ethylenedi-aminetetraacetic acid (EDTA), restoring its functionality for repeated use. The sensor was successfully applied to detect lead in various complex matrices, including biological fluids, environmental water, and food samples, demonstrating its broad applicability and reliability for real-world lead monitoring.

Sustainable Valorization of Rice Straw into Biochar and Carbon Dots Using a Novel One-Pot Approach for Dual Applications in Detection and Removal of Lead Ions

Lead (Pb) is a highly toxic heavy metal that causes significant health hazards and environmental damage. Thus, the detection and removal of Pb2+ ions in freshwater sources are imperative for safeguarding public health and the environment. Moreover, the transformation of single resources into multiple high-value products is vital for achieving sustainable development goals (SDGs). In this regard, the present work focused on the preparation of two efficient materials, i.e., biochar (R-BC) and carbon dots (R-CDs) from a single resource (rice straw), via a novel approach by using extraction and hydrothermal process. The various microscopic and spectroscopy techniques confirmed the formation of porous structure and spherical morphology of R-BC and R-CDs, respectively. FTIR analysis confirmed the presence of hydroxyl (-OH), carboxyl (-COO) and amine (N-H) groups on the R-CDs' surface. The obtained blue luminescent R-CDs were employed as chemosensors for the detection of Pb2+ ions. The sensor exhibited a strong linear correlation over a concentration range of 1 µM to 100 µM, with a limit of detection (LOD) of 0.11 µM. Furthermore, the BET analysis of R-BC indicated a surface area of 1.71 m2/g and a monolayer volume of 0.0081 cm3/g, supporting its adsorption potential for Pb2+. The R-BC showed excellent removal efficiency of 77.61%. The adsorption process followed the Langmuir isotherm model and second-order kinetics. Therefore, the dual use of rice straw-derived provides a cost-effective, environmentally friendly solution for Pb2+ detection and remediation to accomplish the SDGs.

XG and CS-based self-assembled nanocomposite hydrogel embedding fluorescent NCQDs capable of detection and adsorptive removal of the polar MO and Cr(VI) pollutants

Aiming at dealing with organic and inorganic pollutants dissolved in aquatic environments, we introduce self-assembled fluorescent nanocomposite hydrogel based on a binary polysaccharide network (xanthan gum/chitosan) embedding nitrogen-doped carbon quantum dots not only as a hybrid solid optical sensor for detecting Cr(VI) ions but also to remove anionically charged contaminants Cr(VI) and methyl orange (MO) by acting as an adsorbent. This fluorescent nanocomposite achieved a detection limit of 0.29 μM when used to detect Cr(VI) and demonstrated a fluorescence quantum yield of 59.7 %. Several factors contributed to the effectiveness of the adsorption of Cr(VI) and MO in batch studies, including the solution pH, dosage of the adsorbent, temperature, initial contamination level, and contact time. Experimental results showed 456 mg/g maximum adsorption capacity at pH 4 for MO compared to 291 mg/g at pH 2 for Cr(VI) at 25 °C. In addition to conforming to Langmuir's model, Cr(VI) and MO's adsorption kinetics closely matched pseudo-second-order. Using thermodynamic parameters, the results indicate that Cr(VI) and MO adsorb spontaneously and exothermically. Recycling spent adsorbent for Cr(VI) and MO using NaOH at 0.1 M was possible; the respective adsorption efficiency remained at approximately 82.2 % and 83 % after the fifth regeneration cycle.

Regulating the Surface State of Carbon Dots as Ultrahigh-Capacity Adsorbents for Water Treatment

Adsorption is one of the most widely researched and highly effective methods for mitigating the environmental threat posed by recalcitrant dyes in aqueous solutions. This paper presents a solvent-free synthesis method for the rapid and large-scale production of nitrogen (N) and phosphorus (P) co-doped carbon dots (N, P-CDs) which possess specific surface states and outstanding dye adsorption properties. Compared to the undoped CDs, the N, P-CDs not only exhibit a higher yield of solid-state luminescence but also endow them with the efficient adsorption and removal of Congo red (CR) from water. Due to the synergistic effects of π-π stacking, hydrogen bonding and electrostatic attraction, the N, P-CDs exhibit an ultra-high adsorption capacity (3118.87 mg g-1) and a removal efficiency (97.4%, at 500 mg L-1) for CR, and also display excellent selective adsorption in both single-dye and dual-dye systems. This method offers a rational strategy for synthesizing novel CDs-based adsorbents for CR, which provides a demonstration for future dye adsorption studies and practical wastewater treatment applications of CDs.

Use of Interfacial Interactions and Complexation of Carbon Dots to Construct Ultra-Robust and Efficient Photothermal Film From Micro-Carbonized Polysaccharides

Solar energy conversion technologies, particularly solar-driven photothermal conversion, are both clean and manageable. Although much progress has been made in designing solar-driven photothermal materials, significant challenges remain, not least the photobleaching of organic dyes. To tackle these issues, micro-carbonized polysaccharide chains, with carbon dots (CDs) suspended from the chains, are conceived, just like grapes or tomatoes hanging from a vine. Carbonization of sodium carboxymethyl cellulose (CMC) produces just such a structure (termed CMC-g-CDs), which is used to produce an ultra-stable, robust, and efficient solar-thermal film by interfacial interactions within the CMC-g-CDs. The introduction of the CDs into the matrix of the photothermal material effectively avoided the problem of photobleaching. Manipulating the interfacial interactions (such as electrostatic interactions, van der Waals interactions, π-π stacking, and hydrogen bonding) between the CDs and the polymer chains markedly enhances the mechanical properties of the photothermal film. The CMC-g-CDs are complexed with Fe3+ to eliminate leakage of the photothermal reagent from the matrix and to solve the problem of poor water resistance. The resulting film (CMC-g-CDs-Fe) has excellent prospects for practical application as a photothermal film.

Nanotechnology-based optical sensors for Baijiu quality and safety control

Baijiu quality and safety have received considerable attention owing to the gradual increase in its consumption. However, owing to the unique and complex process of Baijiu production, issues leading to quality and safety concerns may occur during the manufacturing process. Therefore, establishing appropriate analytical methods is necessary for Baijiu quality assurance and process control. Nanomaterial (NM)-based optical sensing techniques have garnered widespread interest because of their unique advantages. However, comprehensive studies on nano-optical sensing technology for quality and safety control of Baijiu are lacking. In this review, we systematically summarize NM-based optical sensor applications for the accurate detection and quantification of analytes closely related to Baijiu quality and safety. Furthermore, we evaluate the sensing mechanisms for each application. Finally, we discuss the challenges nanotechnology poses for Baijiu analysis and future trends. Overall, nanotechnological approaches provide a potentially useful alternative for simplifying Baijiu analysis and improving final product quality and safety.

Review of carbon dot-hydrogel composite material as a future water-environmental regulator

As water pollution and scarcity pose severe threats to the sustainable progress of human society, it is important to develop a method or materials that can accurately and efficiently detect pollutants and purify aquatic environments or exploit marine resources. The compositing of photoluminescent and hydrophilic carbon dots (CDs) with hydrogels bearing three-dimensional networks to form CD-hydrogel composites to protect aquatic environments is a "win-win" strategy. Herein, the feasibility of the aforementioned method has been demonstrated. This paper reviews the recent progress of CD-hydrogel materials used in aquatic environments. First, the synthesis methods for these composites are discussed, and then, the composites are categorized according to different methods of combining the raw materials. Thereafter, the progress in research on CD-hydrogel materials in the field of water quality detection and purification is reviewed in terms of the application of the mechanisms. Finally, the current challenges and prospects of CD-hydrogel materials are described. These results are expected to provide insights into the development of CD-hydrogel composites for researchers in this field.

Starch-based hydrogels for environmental applications: A review

Water sources have become extremely scarce and contaminated by organic and inorganic industrial and agricultural pollutants as well as household wastes. Poisoning water resources by dyes and metals is a problem because contaminated water can leak into subsurface and surface sources, causing serious contamination and health problems. Therefore, developing wastewater treatment technologies is valuable. Today, hydrogels have attracted considerable attention owing to their broad applications. Hydrogels are polymeric network compositions with significant water-imbibing capacity. Hydrogels have potential applications in diverse fields such as biomedical, personal care products, pharmaceuticals, cosmetics, and biosensors. They can be prepared by using natural (biopolymers) and synthetic polymers. Synthetic polymer-based hydrogels obtained from petrochemicals are not environmentally benign; thus, abundant plant-based polysaccharides are found as more suitable compounds for making biodegradable hydrogels. Polysaccharides with many advantages such as non-toxicity, biodegradability, availability, inexpensiveness, etc. are widely employed for the preparation of environmentally friendly hydrogels. Polysaccharides-based hydrogels containing chitin, chitosan, gum, starch (St), etc. are employed to remove pollutants, metals, and dyes. Among these, St has attracted a lot of attention. St can be mixed with other compounds to make hydrogels, which remove dyes and metal ions to variable degrees of efficiency. Although St has numerous advantages, it suffers from drawbacks such as low stability, low water solubility, and fast degradability in water which limit its application as an environmental adsorbent. As an effective way to overcome these weaknesses, various modification approaches to form starch-based hydrogels (SBHs) employing different compounds have been reported. The preparation methods and applications of SBH adsorbents in organic dyes, hazardous materials, and toxic ions elimination from water resources have been comprehensively discussed in this review.

Carbon Dot-Stabilized Hydrogel Composite: A New Adsorbent for Efficient and Sustainable Pb(II) Removal

In this paper, a carbon dot hydrogel composite (CDs-Hy) capable of efficiently removing Pb(II) was prepared by hydrogen bonding self-assembly in combination with carbon dots and a hydrogel. CDs-Hy was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and the effect of the adsorption conditions on the adsorption efficiency of CDs-Hy was studied. The results of the study showed that the incorporation of carbon dots, on the one hand, significantly increased the adsorption capacity of the material. On the other hand, it can increase the stability of hydrogels in aqueous solution. The possible adsorption mechanisms were further verified as ion exchange and coordination. CDs-Hy is a novel adsorbent material capable of removing Pb2+ efficiently, which can be reused several times with high stability.