Clustering-Triggered Emission of Carboxymethylated Nanocellulose

A novel approach for the green synthesis of iron nanoparticles using marigold extract, black liquor, and nanocellulose: Effect on marigold growth parameters

This study aimed to investigate a novel method for the green synthesis of iron nanoparticles (FeNPs) using marigold extract (Calendula officinalis L), kraft pulping black liquor, and nanocellulose. Then, the efficacy of FeNPs as a direct nanofertilizer on the growth parameters of marigold was investigated. Characterization techniques including FESEM, EDX, VSM, and FTIR were used to confirm the successful synthesis of FeNPs. The characterization results confirmed the formation and presence of FeNPs in the 20-100 nm range. FeNPs synthesized with nanocellulose notably enhanced marigold growth parameters compared to other materials. However, all nanoparticle variants, including those from marigold extract and black liquor, improved germination, plant height, root length, and plant dry weight compared to the control. Moreover, treatments exhibited higher available iron and total plant iron levels than the control. Thus, employing 10 mg FeNPs (prepared with 5.0 % nanocellulose) appears optimal for enhancing marigold growth and yield.

Synthesis and fluorescent property of carboxymethyl chitosan with different degrees of carboxymethylation and its application for fluorescence turn-on detection of Cd(II) ion

Recently, carboxymethyl chitosan (CMCS) has proved to be an intrinsically fluorescent material with aggregation-induced emission characteristic. In order to elucidate the influence of CMCS's chemical structure and solution behavior on its fluorescent intensity, two series of CMCS with different degrees of carboxymethylation (DCM) are synthesized by adjusting the mass ratio of monochloroacetic acid and sodium hydroxide to chitosan at various reaction temperature and time, and then characterized using Fourier-transform infrared spectroscopy and nuclear magnetic resonance. Their solution behaviors at different pH values are studied via zeta potential and ultraviolet-visible measurements. The data reveal that the isoelectronic point (IEP) of a CMCS decreases with increasing DCM, and all the CMCSs have good water solubility at pH range below their IEPs. Fluorescence spectra indicate that a CMCS shows the highest fluorescent intensity in a slightly acidic environment next to its IEP, and the photoluminescence of a CMCS solution increases significantly after heat treatment above T = 70 °C. Furthermore, we compare for the first time the use of heated CMCS solutions for the fluorescence turn-on detection of cadmium ion in pure and tap water, respectively. The limit of detection is found to be ca. 1 μM for the Cd2+ in pure water.

Polymerization-induced emission (PIE) of multifunctional polyamides synthesized by Ugi polymerization and targeted imaging of lysosomes

In this paper, a series of polyamide derivatives (PAMs) containing morpholine groups were prepared by Ugi polymerization from dialdehyde, diacid, N-(2-aminoethyl)-morpholine and isonitrile compounds as novel multi-responsive fluorescent sensors. As non-conjugated light-emitting polymers, PAMs were endowed with unique polymerization-induced emission (PIE) performance at 450 nm by through-space conjugation (TSC) between heteroatoms and heterocycles. It was also found that PAMs exhibited reversible responses to the external temperature and pH values and became responsive fluorescent switches. In addition, PAMs can specifically recognize Fe³⁺ with a limit of detection (LOD) of 54 nM and the introduction of EDTA reversibly restores the fluorescence of the quenched PAMs-Fe³⁺ system. By virtue of thermosensitivity, PAMs are easily separated from the above system by changing the temperature above or below the lower critical solution temperature (LCST). It is worth noting that PIE-active PAMs with good biocompatibility can selectively accumulate in lysosomes due to the presence of morpholine groups, and its Pearson colocalization coefficient is as higher as 0.91. Furthermore, a PIE-active PAM was successfully used to track exogenous Fe³⁺ in lysosomes. In conclusion, these multi-functional PIE-active PAMs have higher potential applications in biomedical or environmental fields.

Autofluorescence spectroscopy for quantitative analysis of cellulose nanocrystals

The ability to determine the physicochemical properties of nanoparticles, such as cellulose nanocrystals, in suspension is critically important to maximize their potential. Currently, various techniques are required to ascertain different properties, which results in a laborious analysis procedure. Here, autofluorescence arising from the cluster-triggered emission (CTE) photoluminescence mechanism is utilized as an analytical spectroscopic tool to determine multiple properties from one data acquisition sequence. This study confirms that key properties - including the nanoparticle concentration in suspension, the critical concentration for liquid crystal formation, and the surface charge content - can be obtained simultaneously. Measured values are accurate to within 10% of conventional techniques with average residual errors of 0.4 wt% for the critical concentration, and 11 mmol kg^-1 CNC for the surface charge content. This charge-coupled device (CCD) sensor-based methodology is rapid and does not require the addition of further chemicals. These results support the theory behind CTE and represent a new opportunity for quantitatively analysing non-aromatic, heteroatom-containing nanoparticles in flow based on understanding their inter- and intra-particle interactions.

Clustering-Triggered Emission of EPS-605 Nanoparticles and Their Application in Biosensing

Natural carbohydrates with intrinsic luminescent properties have drawn increasing attention thanks to their fundamental importance and promising applications. To expand the range of natural nonconventional biomacromolecule luminogens and to gain deep insights into their emission mechanism, we prepared EPS-605, a naturally occurring spherical nanoparticle based on negatively charged exopolysaccharides (EPS), and studied its emission behavior. It was found that EPS-605 was highly emissive in the aggregate state, such as powder and film. Furthermore, EPS-605 aqueous solutions exhibited concentration-enhanced emission characteristics. According to fluorescence spectra and confocal images, the fluorescence phenomenon of EPS-605 was not affected by the pH value and the carbon sources. The emission behavior of EPS-605 was attributed to the clustering-triggered emission (CTE) mechanism. Moreover, EPS-605 was successfully utilized for Fe3+ detection since its fluorescence could be selectively quenched by Fe3+. It could be used to detect Fe3+ with a low limit of detection (0.06 μM) and a wide detection range from 0.05 to 250 μM. Overall, these findings not only benefit the exploitation of EPS-based nonconventional biomacromolecule luminogens, but also reveal the potential applications of EPS-605 in biosensing/bioimaging, anticounterfeiting, and encryption owing to its excellent biocompatibility, environmental friendliness, and intrinsic photoluminescence property.

Sustainable aggregation-induced emission material based on pectin-l-lysine: Potential antibacterial and monitoring in food spoilage

The demand of smart food detection system which in detecting food spoilage is increasing. In this work, a new type of aggregation-induced emission (AIE) compound was synthesized based on pectin (P) and l-lysine (Lys). P-Lys is an AIE active compound which has the advantages of simple synthesis, easy modification and processability, it also has good water solubility and biocompatibility. Moreover, P-Lys has potential application in detecting Fe³⁺ (oxidation from Fe²⁺) and bacterial in monitoring pork spoilage. In addition, P-Lys also has spectral antibacterial properties which can prevent pork spoilage. The research results shown that P-Lys, as a new type of food testing agent has a useful future in monitoring and protecting the freshness of food.

Chitosan-salicylide Schiff base with aggregation-induced emission property and its multiple applications

Aggregation-induced emission (AIE) active compounds are fascinated due to their unique properties of limiting intramolecular rotation, and they have been developed in the biomedical fields. In this work, AIE material based on the Schiff base compound of chitosan (Cs) and salicylaldehyde (SA) was designed and synthesized. Cs-SA emits weak light in dilute aqueous solution, and emits bright light in concentrated solution and solid, showing obvious AIE performance. In addition, Cs-SA can also be used as a biosensor to detect Fe³⁺, and Cu²⁺, it has good bioimaging behavior. In addition, it can also be used as biosensor to quantitatively detect gram-positive bacteria and gram-negative bacteria, Moreover, Cs-SA shows excellent broad spectrum antibacterial performance in inhibiting E. coli and S. aureus.

Nonconventional luminophores: characteristics, advancements and perspectives

Nonconventional luminophores devoid of remarkable conjugates have attracted considerable attention due to their unique luminescence behaviors, updated luminescence mechanism of organics and promising applications in optoelectronic, biological and medical fields. Unlike classic luminogens consisting of molecular segments with greatly extended electron delocalization, these unorthodox luminophores generally possess nonconjugated structures based on subgroups such as ether (-O-), hydroxyl (-OH), halogens, carbonyl (CO), carboxyl (-COOH), cyano (CN), thioether (-S-), sulfoxide (SO), sulfone (OSO), phosphate, and aliphatic amine, as well as their grouped functionalities like amide, imide, anhydride and ureido. They can exhibit intriguing intrinsic luminescence, generally featuring concentration-enhanced emission, aggregation-induced emission, excitation-dependent luminescence and prevailing phosphorescence. Herein, we review the recent progress in exploring these nonconventional luminophores and discuss the current challenges and future perspectives. Notably, different mechanisms are reviewed and the clustering-triggered emission (CTE) mechanism is highlighted, which emphasizes the clustering of the above mentioned electron rich moieties and consequent electron delocalization along with conformation rigidification. The CTE mechanism seems widely applicable for diversified natural, synthetic and supramolecular systems.

Intrinsic Green Fluorescent Cross-Linked Poly(ester amide)s by Spontaneous Zwitterionic Copolymerization

The spontaneous zwitterionic copolymerization (SZWIP) of 2-oxazolines and acrylic acid affords biocompatible but low molecular weight linear N-acylated poly(amino ester)s (NPAEs). Here, we present a facile one-step approach to prepare functional higher molar mass cross-linked NPAEs using 2,2'-bis(2-oxazoline)s (BOx). In the absence of solvent, insoluble free-standing gels were formed from BOx with different length n-alkyl bridging units, which when butylene-bridged BOx was used possessed an inherent green fluorescence, a behavior not previously observed for 2-oxazoline-based polymeric materials. We propose that this surprising polymerization-induced emission can be classified as nontraditional intrinsic luminescence. Solution phase and oil-in-oil emulsion approaches were investigated as means to prepare solution processable fluorescent NPAEs, with both resulting in water dispersible network polymers. The emulsion-derived system was investigated further, revealing pH-responsive intensity of emission and excellent photostability. Residual vinyl groups were shown to be available for modifications without affecting the intrinsic fluorescence. Finally, these systems were shown to be cytocompatible and to function as fluorescent bioimaging agents for in vitro imaging.

Generating circularly polarized luminescence from clusterization-triggered emission using solid phase molecular self-assembly

Purely-organic clusterization-triggered emission (CTE) has displayed promising abilities in bioimaging, chemical sensing, and multicolor luminescence. However, it remains absent in the field of circularly polarized luminescence (CPL) due to the difficulties in well-aligning the nonconventional luminogens. We report a case of CPL generated with CTE using the solid phase molecular self-assembly (SPMSA) of poly-L-lysine (PLL) and oleate ion (OL), that is, the macroscopic CPL supramolecular film self-assembled by the electrostatic complex of PLL/OL under mechanical pressure. Well-defined interface charge distribution, given by lamellar mesophases of OL ions, forces the PLL chains to fold regularly as a requirement of optimal electrostatic interactions. Further facilitated by hydrogen bonding, the through-space conjugation (TSC) of orderly aligned electron-rich O and N atoms leads to CTE-based CPL, which is capable of transferring energy to an acceptor via a Förster resonance energy transfer (FRET) process, making it possible to develop environmentally friendly and economic CPL from sustainable and renewable materials.

Dramatically Enhanced and Red-shifted Photoluminescence Achieved by Introducing an Electron-withdrawing Group into a Non-traditional Luminescent Small Organic Compound

Small organic compounds without any traditional fluorescent chromophores are generally non-emissive, and only very few are reported to emit weak blue fluorescence. Here we synthesized a non-traditional luminescent small organic compound N-(2,2,2-trifluoroethyl)acrylamide (TFAM) with dramatically enhanced and red-shifted photoluminescence by introducing a strong electron-withdrawing group into acrylamide (AM). Very impressively, TFAM emits cyan (472 nm) and yellow-green (560 nm) fluorescence in solutions and solid state, respectively. TFAM also shows aggregation-induced emission enhancement (AIEE) and excitation-dependent fluorescence (EDF) characteristics, as well as temperature and metal cations-responsive fluorescence. Theoretical calculations show that the introduction of electron-withdrawing group leads to a lower energy gap between the HOMO-LUMO energy levels in TFAM than in AM. And strong cooperative hydrogen bonds are formed in TFAM molecules, resulting in rigidification of molecular conformations. The study provides a strategy for preparing non-traditional luminescent compounds with enhanced and red-shifted photoluminescence.

Seeking brightness from nature: Sustainable AIE macromolecule with clustering-triggered emission of xanthan gum and its multiple applications

Unconventional biomacromolecule luminescent agents have attracted widespread attention due to the potential applications in diverse fields. In order to explore new luminescent agents and gain a comprehensive understanding of their emission mechanism, the emission behavior of xanthan gum was investigated. Xanthan gum shown obvious aggregation-induced emission (AIE) characteristics in concentration solution. Moreover, xanthan gum has shown potential values in intracellular imaging and can be used as a biosensor for detecting Fe³⁺ and Cu²⁺ in human serum.

Wood-Derived Carbon Materials and Light-Emitting Materials

Wood is a sustainable and renewable material that naturally has a hierarchical structure. Cellulose, hemicellulose, and lignin are the three main components of wood. The unique physical and chemical properties of wood and its derivatives endow them with great potential as resources to fabricate advanced materials for use in bioengineering, flexible electronics, and clean energy. Nevertheless, comprehensive information on wood-derived carbon and light-emitting materials is scarce, although much excellent progress has been made in this area. Here, the unique characteristics of wood-derived carbon and light-emitting materials are summarized, with regard to the fabrication principles, properties, applications, challenges, and future prospects of wood-derived carbon and light-emitting materials, with the aim of deepening the understanding and inspiring new ideas in the area of advanced wood-based materials.

Clustering-triggered emission of poly(vinyl) alcohol

PVA can emit blue light under UV light and the mechanism of this fluorescence was studied in this paper. PVA can be added to other materials to broaden their properties. The fluorescence of PVA has great application prospects.

Ecofriendly multifunctional thiolated carboxymethyl chitosan-based 3D scaffolds with luminescent properties for skin repair and theragnostic of tissue regeneration

Luminescent biopolymers, namely carboxymethyl chitosan, have become a target of attention due to their potential for biomedical applications. In this context, biomaterials capable of improving theragnostic tissue regeneration and provide a tissue repair remain a challenge. This study introduces a new 3D scaffold based on two innovative thiolated carboxymethyl chitosan with cysteine (CMCCys) and 11-mercaptoundecanoic acid (CMCMerc) resulting in enhanced fluorescence of CMC for repair and theragnostic of tissue regeneration. Those thiolated CMCs were intensively characterized by spectroscopy techniques (FTIR, NMR), swelling degree, chemical stability (Gel-fraction, GF) and morphological analysis (SEM, microtomography, BET). In addition, the photoluminescence properties were evaluated and cytocompatibility was performed via in vitro bioassays. The results demonstrated that those scaffolds presented interconnected 3D porous (porosity > 80%), a great GF, and a high degree of thiolation (2%-11%). Furthermore, the spectroscopy analysis elucidated a significant disulfide bond formation, which guaranteed mechanical stability for applications in tissue engineering (elastic modulus, (22 ± 3) kPa and (35 ± 2) kPa, for CMCCys and CMCMerc, respectively). Additionally, the incorporation of thiol group improved the fluorescence of CMC and they presented cytocompatibility > 90%. Thus, for the first time, a multifunctional 3D CMC thiomer was produced for applications in repair and theragnostic of tissue regeneration.

Radiation-Induced In Situ-Printed Nonconjugated Fluorescent Nonwoven Fabric with Superior Fluorescent Properties

A new technique is proposed for the in situ printing of fluorescent fabrics with superior fluorescent properties that have the potential for continuous roll-to-roll production in the industry. Nonconjugated chemical moieties were covalently connected to polyethylene/polypropylene nonwoven fabric (PE/PP NWF) to successfully prepare fluorescent PE/PP NWF, which emits a bright blue light and has a high quantum yield (∼83.35%) that can be attributed to a unique aggregation-induced emission effect. The fluorescent PE/PP NWF exhibits excellent fluorescent stability under high shear forces during accelerated laundering and in harsh chemical environments. The fluorescent PE/PP NWF can also be tailored into diverse shapes and printed in situ with high resolution. The versatility of the method was also demonstrated by fabricating fluorescent materials with different polymer matrices such as Nylon 66 fiber and PE terephthalate membrane.

Hydrophobized cellulose nanocrystals enhance xanthan and locust bean gum network properties in gels and emulsions

Locust bean/xanthan gum (LBG/XG) synergistic networks have previously been well studied, with evidence that junction zones between the two polymers result in hydrophobic domains. Here we report on the effect of both hydrophilic and hydrophobic cellulose nanocrystals (CNCs) on the rheological properties of the individual gums, the gum networks, and emulsion gels consisting of the gum network and corn oil. We also take advantage of differences in the autofluorescent spectra for each of the components to map their distribution within the gel and emulsion gel systems. Whilst both types of CNC confer thermal stability to the systems, hydrophilic CNCs induce minor changes in rheological properties of synergistic gels and prove to be detrimental to the stability of the emulsion gels. In contrast, hydrophobic CNCs associate with the LBG/XG network, affecting the rheological response. Their inclusion in the emulsion gel system results in smaller, more homogeneously distributed oil droplets with a resultant increase in the storage modulus by an order of magnitude compared to the CNC-free and hydrophilic CNC systems. We conclude that hydrophobic CNCs play a critical role in stabilising LBG/XG network gels and emulsions.

Biomass-Based Polymer Nanoparticles With Aggregation-Induced Fluorescence Emission for Cell Imaging and Detection of Fe3+ Ions

Polymeric nanoparticles, which show aggregation-induced luminescence emission, have been successfully prepared from larch bark, a natural renewable biomass resource, in a simple, rapid ultrasonic fragmentation method. The structure, element, particle size and molecular weight distribution of larch bark extracts (LBE) were studied by FTIR, XPS, TEM, XRD and linear mode mass spectrometry, respectively. LBE was found containing large numbers of aromatic rings, displaying an average particle size of about 4.5 nm and mainly presenting tetramers proanthocyanidins. High concentration, poor solvent, low temperature and high viscosity restricted the rotation and vibration of the aromatic rings in LBE, leading to the formation of J-aggregates and enhancing the aggregation-induced fluorescence emission. LBE possessed good resistance to photobleaching under ultraviolet light (200 mW/m²). Cytotoxicity experiments for 24 h and flow cytometry experiments for 3 days proved that even the concentrations of LBE as high as 1 mg/mL displayed non-toxic to MG-63 cells. Therefore, LBE could be employed for MG-63 cell imaging, with similar nuclear staining to the DAPI. The effects of different metal ions on the fluorescence emission intensity of LBE were analyzed and exhibited that Fe³⁺ owned obvious fluorescence quenching effect on LBE, while other metal ions possessed little or weak effect. Furthermore, the limit of detection (LOD) of Fe³⁺ was evaluated as 0.17 μM.

Current State of Applications of Nanocellulose in Flexible Energy and Electronic Devices

Novel and unique applications of nanocellulose are largely driven by the functional attributes governed by its structural and physicochemical features including excellent mechanical properties and biocompatibility. In recent years, thousands of groundbreaking works have helped in the development of targeted functional nanocellulose for conductive, optical, luminescent materials, and other applications. The growing demand for sustainable and renewable materials has led to the rapid development of greener methods for the design and fabrication of high-performance green nanomaterials with multiple features, and consequently new challenges and opportunities. The present review article discusses historical developments, various fabrication and functionalization methods, the current stage, and the prospects of flexible energy and hybrid electronics based on nanocellulose.

Enhanced fluorescence of carboxymethyl chitosan via metal ion complexation in both solution and hydrogel states

Recently, biopolymer-based non-traditional luminogens had attracted a great deal of interest because of their potential applications in biomedical field. Herein, we report for the first time that carboxymethyl chitosan (CMCh) can exhibit strong blue fluorescence at λ = 436.8 nm when brought in contact with zinc ion (Zn²⁺) in both solution and hydrogel states. The resultant CMCh-Zn sample exhibits a typical fluorescence lifetime of 3.68 ns and a quantum yield of 6.8%. The fluorescence behaviors of CMCh-Zn samples at different excitation wavelengths, CMCh concentrations, temperature, and pH values, are also investigated. The results clearly indicate clustering-triggered emission characteristic of the CMCh-Zn. In order to further elucidate the chemical nature of this new fluorescence system, a series of CMCh-Zn samples are characterized by using ultraviolet-visible spectrometer, Fourier-transform infrared spectrometer and X-ray diffractometer. The data suggest that the metal-ligand complexation of CMCh with Zn²⁺ account for the generation of such an enhanced fluorescence.

Employing photoluminescence to rapidly follow aggregation and dispersion of cellulose nanofibrils

Multichannel confocal spectroscopy enables tracking of time dependent, spatially resolved changes in the physicochemical environment of cellulose nanofibrils due to variation in emission intensity ratios.