A polyethylenimine/salicylaldehyde modified cellulose Schiff base for selective and sensitive Fe3+ detection

Diaminonaphthalene functionalized LUS-1 as a fluorescence probe for simultaneous detection of Hg2+ and Fe3+ in Vetiver grass and Spinach

One of the important problems in the environment is heavy metal pollution, and fluorescence is one of the best methods for their detection due to its sensitivity, selectivity, and relatively rapid and easy operation. In this study, 1,8-diaminonaphthalene functionalized super-stable mesoporous silica (DAN-LUS-1) was synthesized and used as a fluorescence probe to identify Hg2+ and Fe3+ in food samples. The TGA and FT-IR spectra illustrated that 1,8-diaminonaphthalene was grafted into LUS-1. XRD patterns verified that the LUS-1 and functionalized mesoporous silica have a hexagonal symmetrical array of nano-channels. SEM images showed that the rod-like morphology of LUS-1 was preserved in DAN-LUS-1. Also, surface area and pore diameter decreased from 824 m2 g⁻1 and 3.61 nm for the pure LUS-1 to 748 m2 g⁻1 and 3.43 nm for the DAN-LUS-1, as determined by N₂ adsorption-desorption isotherms. This reduction demonstrated that 1,8-diaminonaphthalene immobilized into the pore of LUS-1. The DAN-LUS-1 fluorescence properties as a chemical sensor were studied with a 340/407 nm excitation/emission wavelength that was quenched by Hg2+ and Fe3+ ions. Hg2+ and Fe3+ were quantified using the fluorescence response in the working range 8.25-13.79 × 10-6 and 3.84-10.71 × 10-6 mol/L, with detection limits of 8.5 × 10-8 M and 1.3 × 10-7 M, respectively. Hg2+ and Fe3+ were measured in vetiver grass and spinach. Since the Fe3+ quenching can move in the opposite direction with sodium hexametaphosphate (SHMP) as a hiding compound for Fe3+, consequently, the circuit logic system was established with Fe3+, Hg2+, and SHMP as inputs and the fluorescent quench as the output.

Tree transpiration-inspired cellulose aerogel with engineered cold-evaporated surface for promoting structural stability and minimizing energy loss

Solar-driven evaporation technology could significantly relieve the fresh-water crisis in the world. However, several problems, such as poor structural stability, low photothermal conversion capacity, and single heat source of traditional evaporators limited the promotion of fresh-water production efficiency. Herein, inspired by tree transpiration, we report a hydrophilic three-dimensional (3D) cellulose-based evaporator similar to the root of a tree, which can pump the bottom water to the evaporation surface for vapor generation. The aldehyde-based cellulose nanocrystals/ethylene imine polymer (ACP) aerogel was developed through Schiff base reaction to enhance the chain entangle capacity of the cellulose nanocrystals (CNCs) aerogel in water. Coating the ACP aerogel with lignin-derived photothermal material created the double-layered solar-driven evaporator (ACP-7LM), achieving a remarkable surface temperature of 35.9 °C in water under 1 sun irradiation for 1 h. The ACP-7LM exhibited an impressive evaporation rate of 1.60 kg m-2 h-1, leveraging its structural stability and excellent photothermal conversion. Increasing the cold evaporation surface (adjusting exposure height from 0 cm to 4 cm) of ACP-7LM aerogel maintained a lower temperature compared to ambient temperature on the side surface during evaporation, which harvest heat energy from environment and minimize energy loss. This enhanced environmental heat absorption boosted the ACP-7LM's evaporation rate to 3.76 kg m-2 h-1, a 2.35-fold increase over the ACP-7LM (0 cm). This solar-driven evaporator offers an efficient, innovative approach to elevate evaporation rates and address the global water crisis by simultaneously enhancing heat absorption capacity and photothermal conversion efficiency.

PEI-based functional materials: Fabrication techniques, properties, and biomedical applications

Cationic polymers have recently attracted considerable interest as research breakthroughs for various industrial and biomedical applications. They are particularly interesting due to their highly positive charges, acceptable physicochemical properties, and ability to undergo further modifications, making them attractive candidates for biomedical applications. Polyethyleneimines (PEIs), as the most extensively utilized polymers, are one of the valuable and prominent classes of polycations. Owing to their flexible polymeric chains, broad molecular weight (MW) distribution, and repetitive structural units, their customization for functional composites is more feasible. The specific beneficial attributes of PEIs could be introduced by purposeful functionalization or modification, long service life, biocompatibility, and distinct geometry. Therefore, PEIs have significant potential in biotechnology, medicine, and bioscience. In this review, we present the advances in PEI-based nanomaterials, their transfection efficiency, and their toxicity over the past few years. Furthermore, the potential and suitability of PEIs for various applications are highlighted and discussed in detail. This review aims to inspire readers to investigate innovative approaches for the design and development of next-generation PEI-based nanomaterials possessing cutting-edge functionalities and appealing characteristics.

New fluorescent Schiff base modified nanocellulose-based chemosensors for the selective detection of Fe3+, Zn2+ and Cu2+ in semi-aqueous media and application in seawater sample

Stimulus-responsive fluorescent-modified biopolymers have received significant attention in the field of chemosensors. Herein, four new fluorescent dyes, namely, S1: (PDA-DANC), S2: (SAL-PDA-DANC), S3: (BrSAL-PDA-DANC) and S4: (ClSAL-PDA-DANC) have been successfully synthesized from 2,3-dialdehyde nanocellulose (DANC) for the detection of heavy metals. The microstructural and photophysical properties of nanocellulose (NC), microcrystalline cellulose (DANC) and the synthesized S1 to S4 dyes were investigated by FT-IR, SEM-EDX, XRD, TGA, DLS and photoluminescence. NC, obtained from conversion of MCC, shows an average size of 802.4 nm with 0.141 of polydispersity index (PdI), and a crystalline index (CI) of 82.40 % and crystallite size of 4.68 nm. The synthesized dyes present good fluorescent properties and have been therefore exploited for developing new probes for heavy metal ions detection. Remarkable "turn off" and/or "turn on" behaviors with Fe3+ and Cu2+ and with Zn2+ in DMF/water solution have been demonstrated, allowing the sensitive and selective determination of these heavy metal ions with a low limit of detection (LOD). Finally, the evaluation of the Fe3+ sensing in a real seawater sample was investigated.

Readily soluble cellulose-based fluorescent probes for the detection and removal of Fe3+ ion

Cellulose is an economical, biodegradable, widely available, and eco-friendly natural macromolecule. But its utilization has been restricted due to its insolubility in water and common organic solvents. In this work, soluble fluorescent probes based on cellulose were synthesized. Firstly, the primary hydroxyl group in glucose units was reacted with SOCl2 to introduce Cl and obtain chloro-cellulose (Cell-Cl). This operation breaks down the regular structure and hydrogen bonding of the original cellulose, enabling it to dissolve in DMSO. Secondly, the Cell-Cl reacted with CS2 and 2-mercaptobenzothiazole to obtain a cellulose-based macromolecular RAFT reagent (Cell-CTA). Finally, the fluorescent monomers which bears -C=C- and naphthalimide, and methacrylic acid (MAA) were grafted onto the main chain of cellulose through RAFT polymerization. Thus, cellulose-based readily soluble macromolecular fluorescent probes were obtained. The cellulose-based probes can specifically recognize Fe3+ in pure water and can be recycled and regenerated. Additionally, the cellulose-based probes exhibit remarkable adsorption and separation properties for Fe3+ ions. The modification of cellulose decreases its crystallinity and introduces hydrophilic groups and fluorophores, which enables cellulose to be soluble in both pure water and the organic solvent DMSO. This work expands the application range of cellulose-based copolymers.

Schiff base synergized with protonation of PEI to achieve smart antibacteria of nanocellulose packaging films

Microbial growth and reproduction can cause food spoilage. Developing the controlled release packaging films for food is an ideal solution. In this study, polyethyleneimine (PEI) was grafted to cellulose nanofibers (CNF) films by Schiff base, and when the CNF/PEI films were stimulated by pH, PEI released from the CNF/PEI films due to Schiff base hydrolysis, improving the antibacterial efficiency of PEI. Stimulated by acid with pH of 4, the PEI cumulative release rate of the CNF/PEI₈₀₀ and the CNF/PEI₂₀₀₀ films reached to 92.90 % and 87.28 %, respectively. At the same time, the amino groups of PEI protonated by obtaining H⁺, the charge density increased, and PEI molecular chains extended, enhancing the antibacterial activity of films. The Zeta potential value on the surface of the CNF/PEI film increased with the decrease of pH value. Schiff base synergized with protonation of PEI to achieve smart antibacteria of CNF packaging films. The antibacterial rates of the film against L. monocytogenes and E. coli were 94.7 % and 90.6 % at pH 4, but 29.5 % and 23.6 % at pH 8, respectively. The developed films also had good barrier properties of oxygen, visible light and mechanical properties, and had an attractive application prospect in food preservation to control release of antibacterial agent.

Cellulose Modified with Polyethylenimine (PEI) Using Microwave Methodology for Adsorption of Chromium from Aqueous Solutions

A large amount of agricultural waste was used to prepare cellulose (Cel) and then the surface was modified with PEI (Cel-PEI) using the microwave method. To be used as a metal adsorbent, the adsorption of Cr (VI) from an aqueous solution by Cel-PEI was measured using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) techniques. The parameters of Cr (VI) adsorption in solution by the Cel-PEI adsorbent were as follows: the pH of the solution was 3, the concentration of the chromium solution was 100 mg/L, and the adsorption time was 180 min at 30 °C using 0.01 g of adsorbent. Cel-PEI had a Cr (VI) adsorption capacity of 106.60 mg/g, while the unadjusted Cel was 23.40 mg/g and the material recovery showed a decrease in efficiency of 22.19% and 54.27% in the second and third cycles, respectively. The absorption isotherm of chromium adsorption was also observed. The Cel-PEI material conformed to the Langmuir model with an R² value of 0.9997. The kinetics of chromium adsorption showed that under pseudo-second-order analysis, with R² values of 0.9909 and 0.9958 for Cel and Cel-PEI materials, respectively. The G° and H° values of the adsorption process were negative, indicating that the adsorption is spontaneous and that the adsorption process is exothermic. The efficient preparation adsorbent materials for Cr (VI) was achieved using a short microwave method that is low-cost and environmentally friendly for use in the treatment of Cr-contaminated wastewater.

N-alkylation briefly constructs tunable multifunctional sensor materials: Multianalyte detection and reversible adsorption

A series of N-alkyl-substituted polybenzimidazoles (SPBIs), synthesized by simple condensation and N-alkylation, act as functional materials with tunable microstructures and sensing performance. For their controllable morphologies, the formation of nano-/microspheres is observed at the n(RBr)/n(PBI) feed ratio of 5:1. Products with different degrees of alkylation can recognize metal ions and nitroaromatic compounds (NACs). For example, SPBI-c, obtained at the feed ratio of 1:1, can selectively detect Cu2+, Fe3+, and NACs. By contrast, SPBI-a, obtained at the feed ratio of 0.1:1, can exclusively detect Cu2+ with high sensitivity. Their sensing mechanisms have been studied by FT-IR spectroscopy, SEM, XPS, and DFT calculations. Interestingly, the SPBIs can adsorb Cu2+ in solution and show good recyclability. These results demonstrate that polymeric materials with both sensing and adsorption applications can be realized by regulating the alkylation extent of the main chain, thus providing a new approach for the facile synthesis of multifunctional materials.

Dendrimer-assisted boronate affinity cellulose foams for the efficient and selective separation of glycoproteins

Surfaces engineered to identify and enrich glycoproteins are of considerable interest in the diagnostic and detection fields. A boronate affinity (BA) material was proposed as a potential candidate for the isolation of glycoproteins. However, this material has the disadvantages of low efficiency and non-degradability. Herein, a novel dendrimer-amplified BA cellulose foam (PEI-PBA-CF) was fabricated via a mild two-step approach. The as-prepared PEI-PBA-CF exhibited a rapid adsorption equilibrium rate (within 60 min) and outstanding adsorption capacity for horseradish peroxidase (537.4 mg g^-1) and ovalbumin (495.5 mg g^-1). Furthermore, competitive adsorption experiments demonstrated that PEI-PBA-CF could achieve selective separation and purification of glycoproteins from complex biological samples due to the synergistic effect of the improved BA capacity by the dendrimer and the well-interconnected porous structure of the biomass matrix. Consequently, these cellulose foams might present new application opportunities in analytical and biomedical fields.

A Multifunctional 3D Supermolecular Co Coordination Polymer With Potential for CO2 Adsorption, Antibacterial Activity, and Selective Sensing of Fe3+/Cr3+ Ions and TNP

A 3D supermolecular structure [Co₃(L)₂ (2,2′-bipy)₂](DMF)₃(H₂O)₃ 1) (H₃L = 4,4′,4″-nitrilotribenzoic acid) has been constructed based on H₃L, and 2,2′-bipy ligands under solvothermal conditions. Compound 1 can be described as a (3, 6)-connected kgd topology with a Schläfli symbol (4³)₂(4⁶.6⁶.8³) formed by [Co₃(CO₂)₆] secondary building units. The adsorption properties of the activated sample 1a has been studied; the result shows that 1a has a high adsorption ability: the CO₂ uptakes were 74 cm³·g⁻¹ at 273 K, 50 cm³·g⁻¹ at 298 K, the isosteric heat of adsorption (Q_st) is 25.5 kJ mol⁻¹ at zero loading, and the N₂ adsorption at 77 K, 1 bar is 307 cm³ g⁻¹. Magnetic measurements showed the existence of an antiferromagnetic exchange interaction in compound 1, besides compound 1 exhibits effective luminescent performance for Fe³⁺/Cr³⁺ and TNP.

Synthesis of a novel superabsorbent with slow-release urea fertilizer using modified cellulose as a grafting agent and flexible copolymer

In this work, a number of glucose unites in polymeric structure of cellulose was converted to 2,4-dihydroxy-3-(1-hydroxy-2-oxoethoxy)butanal (cellulose containing di aldehyde units (CCDAUs)) by oxidation with sodium periodate, followed by condensation with acetone to produce 5,7-dihydroxy-6-((1-hydroxy-4-oxopent-2-en-1-yl)oxy)hept-3-en-2-one unites (cellulose containing di ene units (CCDEUs)). This modified cellulose was characterized by different methods and applied as a copolymer and grafting agent to synthesize an eco-friendly (CCDEUs-g-poly(AA)/urea) superabsorbent with slow-release urea fertilizer. The created double bonds in C₂ and C₃ positions of β-d-glucose units increased the linkage between cellulose and acrylic acid, leading to the formation of a strong network for slow-release urea fertilizer. Also, this modification created an expanded network for storage a high amount of water by increasing the cellulose flexibility. The reaction conditions for modification and synthesis of the superabsorbent, the oxidation degree value of glucose units, kinetics models, the effect of different saline solutions, various pH and reswelling time on the water absorbency, water retention capacity, reusability, biodegradability, and slow-release property were investigated. Also, the effect of synthesized CCDEUs-g-poly(AA)/urea on plant growth was tested and excellent results were obtained.

Simple C3-symmetric triaminoguanidine-triphenylamine conjugate as an efficient colorimetric sensor for Cu(II) and fluorescent sensor for Fe(III) ions

The design and construction of novel C₃-symmetric triaminoguanidine-triphenylamine conjugate (L) has been demonstrated and it displays positive solvatochromic behaviour with an increase in solvent polarity. The probe L acts as a selective colorimetric sensor for Cu²⁺ ions over other metal ions. Further, it shows high selective and sensitive detection of Fe³⁺ ions through turn-on fluorescence response. Moreover, the detection limits for Cu²⁺ and Fe³⁺ ions were found to be within the allowable range of the World Health Organisation (30 μM). The real-time application of the probe was showed by paper strip experiments as well as detection of Fe³⁺ ions in pharmaceutical tablets.

Recent advances in cellulose-based membranes for their sensing applications

ABSTRACT

In recent years, sensing applications have played a very important role in various fields. As a novel natural material, cellulose-based membranes with many merits can be served as all kinds of sensors. This review summarizes the recent progress of cellulose membranes as sensors, mainly focusing on their preparation processes and sensing properties. In addition, the opportunities and challenges of cellulose membrane-based sensors are also prospected. This review provides some references for the design of cellulose membrane materials for sensing applications in the future.

Synthesis, crystal structures, and luminescent properties of Zn(ii), Cd(ii), Eu(iii) complexes and detection of Fe(iii) ions based on a diacylhydrazone Schiff base

Acylhydrazone Schiff bases are rich in N and O atoms to coordinate with metal ions to form multidentate complexes.