A sulphonated carbon dot-chitosan hybrid hydrogel nanocomposite as an efficient ion-exchange film for Ca2+ and Mg2+ removal

Polymeric hydrogels-based materials for wastewater treatment

Low-cost and reliable wastewater treatment is a relevant issue worldwide to reduce the concentration of environmental pollutants. Industrial effluents containing dyes, heavy metals, and other inorganic and organic compounds can pollute water resources; therefore, novel technologies are required to mitigate and control their release into the environment. Adsorption is one of the simplest methods for treating contaminated water in which a wide spectrum of adsorbents can be used to remove emerging compounds. Hydrogels are interesting materials with high adsorption capacities that can be synthesized via green routes. These adsorbents are promising for large-scale industrial wastewater treatment applications; however, gaps still exist in achieving sustainable commercial implementation. This review focuses on the discussion and analysis of preparation, characterization, and adsorption properties of hydrogels for water purification. The advantages of these polymeric materials for water treatment were analyzed, including their performance in the removal of different organic and inorganic contaminants. Recent advances in the functionalization of hydrogels and the synthesis of novel composites have also been described. The adsorption capacities of hydrogel-based adsorbents are higher than 500 mg/g for different organic and inorganic pollutants, and can reach values of up to >2000 mg/g for organic compounds, significantly outperforming other materials reported for water cleaning. The main interactions involved in the adsorption of water pollutants using hydrogel-based adsorbents were described and explained to allow the interpretation of their removal mechanisms. The current challenges in the implementation of hydrogels for water purification in real-life operations are also highlighted. This review provides an updated picture of hydrogels as interesting materials to address water depollution worldwide.

Polysaccharide-based C-dots and polysaccharide/C-dot nanocomposites: fabrication strategies and applications

C-dots are a new class of materials with vast applications. The synthesis of bio-based C-dots has attracted increasing attention in recent years. Polysaccharides being the most abundant natural materials with high biodegradability and no toxicity have been the focus of researchers for the synthesis of C-dots. C-dots obtained from polysaccharides are generally fabricated via thermal procedures, carbonization, and microwave pyrolysis. Small size, photo-induced electron transfer (PET), and highly adjustable luminosity behavior are the most important physical and chemical properties of C-dots. However, C-dot/polysaccharide composites can be introduced as a new generation of composites that combine the features of both C-dots and polysaccharides having a wide range of applications in biomedicines, biosensors, drug delivery systems, etc. This review demonstrates the features, raw materials, and methods used for the fabrication of C-dots derived from different polysaccharides. Furthermore, the properties, applications, and synthesis conditions of various C-dot/polysaccharide composites are discussed in detail.

Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review

Due to the wonderful property of hydrogels, they can provide a platform for a wide range of applications. Recently, there is a growing research interest in the development of potential hydrogel adsorbents in wastewater treatment due to their adsorption ability toward aqueous pollutants. It is important to prepare such a hydrogel that possesses appropriate robustness, adsorption capacity, and adsorption efficiency to meet the need of water treatment. In order to improve the property of hydrogels, much effort has been made by researchers to modify hydrogels, among which incorporating inorganic components into the polymeric networks is the most common method, which can reduce the product cost and simplify the preparation procedure. Not only can hydrogel be applied as adsorbent, but it also can be used as matrix for catalyst immobilization. In this review, the key advancement on the preparation and modification of hydrogels is discussed, with special emphasis on the introduction of inorganic materials into polymeric networks and consequential changes in the properties of mechanical strength, swelling, and adsorption. Besides, hydrogels used as adsorbents for removal of dyes and inorganic pollutants have been widely explored, but their use for adsorbing emerging contaminants from aqueous solution has not received much attention. Thus, this review is mainly focused on hydrogels' application in removing emerging contaminants by adsorption. Furthermore, hydrogels can be also applied in immobilizing catalysts, such as enzyme and photocatalyst, to remove pollutants completely and avoid secondary pollution, so their progress as catalyst matrix is overviewed.

Hydrogel applications for adsorption of contaminants in water and wastewater treatment

During the last decade, hydrogels have been used as potential adsorbents for removal of contaminants from aqueous solution. To improve the adsorption efficiency, there are numerous different particles that can be chosen to encapsulate into hydrogels and each particle has their respective advantages. Depending on the type of pollutants and approaching method, the particles will be used to prepare hydrogels. The hydrogels commonly applied in water/wastewater treatment was mainly classified into three classes according to their shape included hydrogel beads, hydrogel films, and hydrogel nanocomposites. In review of many recently research papers, we take a closer look at hydrogels and their applications for removal of contaminants, such as heavy metal ion, dyes, and radionuclides from water/wastewater in order to elucidate the reactions between contaminants and particles and potential for recycling and regeneration of the post-treatment hydrogels. Graphical abstract ᅟ.

Nitrogen-doped carbon nanodots for bioimaging and delivery of paclitaxel

Carbon nanodots (CNDs) hold great potential in imaging and drug delivery applications. In this study, nitrogen-doped CNDs (NCNDs) were coupled to the anticancer agent paclitaxel (PTX) through a labile ester bond. NCNDs showed excellent cell viability and endowed the NCND-PTX conjugate with good water solubility. The hybrid integrates the optical properties of the nanodots with the anticancer function of the drug into a single unit. Cytotoxicity was evaluated in breast, cervix, lung, and prostate cancer cell lines by the MTT assay while the cellular uptake was monitored using confocal microscopy. NCND-PTX induced apoptosis in cancer cells exhibiting slightly better anticancer activity compared to the drug alone. Moreover, the course of the NCND-PTX interaction with cancer cells was monitored using an xCELLigence system. The NCND-based conjugate represents a promising platform for bioimaging and drug delivery.

Carbon Dots as Nanodispersants for Multiwalled Carbon Nanotubes: Reduced Cytotoxicity and Metal Nanoparticle Functionalization

The colloidal stabilization of multiwalled carbon nanotubes (MWCNTs) in an aqueous medium through noncovalent interactions has potential benefits toward the practical use of this one-dimensional carbonaceous material for biomedical applications. Here, we report that fluorescent carbon nanodots can efficiently function as dispersing agents in the preparation of stable aqueous suspensions of CNTs at significant concentrations (0.5 mg/mL). The amphiphilic nature of carbon dots with a hydrophobic graphitic core could effectively interact with the CNT surface, whereas hydrophilic oxygenated functionalization on the C-dot surface provided excellent water dispersibility. The resultant CNT-C-dot composite showed significantly reduced cytotoxicity compared to that of unmodified or protein-coated CNTs, as demonstrated by cell viability and proliferation assays. Furthermore, the reducing capability of C-dots could be envisaged toward the formation of a catalytically active metal nanoparticle-CNT-C-dot composite without the addition of any external reducing or stabilizing agents that showed excellent catalytic activity toward the reduction of p-nitrophenol in the presence of NaBH₄. Overall, the present work establishes C-dots as an efficient stabilizer for aqueous dispersions of CNTs, leading to an all-carbon nanocomposite that can be useful for different practical applications.

Luminescent supramolecular hydrogels from a tripeptide and nitrogen-doped carbon nanodots

The combination of different components such as carbon nanostructures and organic gelators into composite nanostructured hydrogels is attracting wide interest for a variety of applications, including sensing and biomaterials. In particular, both supramolecular hydrogels that are formed from unprotected D,L-tripeptides bearing the Phe-Phe motif and nitrogen-doped carbon nanodots (NCNDs) are promising materials for biological use. In this work, they were combined to obtain luminescent, supramolecular hydrogels at physiological conditions. The self-assembly of a tripeptide upon application of a pH trigger was studied in the presence of NCNDs to evaluate effects at the supramolecular level. Luminescent hydrogels were obtained whereby NCND addition allowed the rheological properties to be fine-tuned and led to an overall more homogeneous system composed of thinner fibrils with narrower diameter distribution.