Solvent Exchange Procedure Research Articles

Thermal insulating, flame retardant, and superhydrophobic polybenzoxazine/silica aerogels fabricated in water-ethanol solvent using eco-friendly method

Polybenzoxazine (PBz) aerogels have garnered considerable attention as an innovative and excellent thermal insulation material, celebrated for its lightweight, low thermal conductivity, and outstanding mechanical properties. However, the use of high boiling point toxic solvents in the preparation process requires a cumbersome solvent exchange procedure coupled with insufficient flame-retardant properties, which hinder the potential application of PBz aerogels. Herein, we employed tetraethyl orthosilicate (TEOS) into PBz using an easy, eco-friendly, and cost-less process to achieve hybrid structure polybenzoxazine/silica (PBz/SiO2) aerogels, by thermal catalysis (72 °C) ring-opening polymerization and polycondensation in water-ethanol solvent without any catalysts. The resulting PBz/SiO2 aerogels were characterized with low density (0.181 g/cm3), low thermal conductivity (0.0315 W/(m·K)), excellent flame-retardancy (PHRR value of 32.3 W/g and THR value of 6.3 kJ/g), and superhydrophobicity (the water contact angle up to 155°). Environment-friendly preparation strategy for the PBz/SiO2 aerogels with excellent comprehensive performance, poised to play a pivotal role in energy-saving buildings and fire-resistant applications.

Influence of Defects and Charges on the Colloidal Stabilization of Graphene in Water.

Mastering graphene preparation is an essential step to its integration into practical applications. For large-scale purposes, full graphite exfoliation appears as a suitable route for graphene production. However, it requires overpowering attractive van der Waals forces demanding large energy input, with the risk of introducing defects in the material. This difficulty can be overcome by using graphite intercalation compounds (GICs) as starting material. The greater inter-sheet separation in GICs (compared with graphite) allows the gentler exfoliation of soluble graphenide (reduced graphene) flakes. A solvent exchange strategy, accompanied by the oxidation of graphenide to graphene, can be implemented to produce stable aqueous graphene dispersions (Eau de graphene, EdG), which can be readily incorporated into many processes or materials. In this work, we prove that electrostatic forces are responsible for the stability of fully exfoliated graphene in water, and explore the influence of the oxidation and solvent exchange procedures on the quality and stability of EdG. We show that the amount of defects in graphene is limited if graphenide oxidation is carried out before exposing the material to water, and that gas removal of water before the incorporation of pre-oxidized graphene is advantageous for the long-term stability of EdG.

Kinetically Controlled Star Copolymer Self-Assembly for Rapid Fabrication of Nanoparticles with High Encapsulation Capacity.

Rapid and scalable self-assembly of an amphiphilic 21-arm star copolymer, (polystyrene-block-polyethylene glycol)21 [(PS-b-PEG)21 ] in aqueous solution has been performed by reverse solvent exchange procedure. Transmission electron microscope (TEM) and nanoparticle tracking analysis (NTA) reveal the formation of nanoparticles with narrow size distribution. Further investigation indicates a kinetically controlled self-assembly mechanism of the copolymers, in which the star topology of the amphiphilic copolymer and deep quenching condition by reverse solvent exchange are key to accelerate intrachain contraction of the copolymer during phase separation. When interchain contraction dominant over interchain association, nanoparticles with low aggregation number could be formed. Thanks to the high hydrophobic contents of the (PS-b-PEG)21 polymers, the resulted nanoparticles could encapsulate a high capacity of hydrophobic cargo up to 19.84 %. The kinetically controlled star copolymer self-assembly process reported here provides a platform for the rapid and scalable fabrication of nanoparticle with high drug loading capacity (LC), which may find broad range of applications in, for example drug delivery, nanopesticide.

Ultralow thermal conductivity of single-atom doped carbon aerogel synthesized with a facile ambient-pressure-drying strategy

Carbon aerogel is an attractive material for thermal insulation due to the porous character and high stability at high temperature. However, the wide application of carbon aerogel for thermal insulation is hindered by complicated supercritical-drying technology and high thermal conductivity of the pure carbon skeleton. Herein, a facile ambient-pressure-drying technology is developed for synthesizing Fe–N4 doped carbon aerogel through catalyzing the polymerization reaction of monomers under a Fe sol, with copolymer F127 as enhancement phase for wet-hydrogel. The whole process does not have any solvent exchange or aging procedure. The prepared carbon aerogel has an ultralow thermal conductivity of 0.048 W/(m ∙ K) at room temperature, with negligible 2% shrinkage during ambient-pressure-drying process and excellent mechanical behavior with stress of 0.58 MPa at 10% strain. The thermal conductivity of carbon-fiber reinforcement carbon aerogel is 0.158 W/(m ∙ K) at 1100 °C, and has an elasticity modulus of 108.3 MPa. Based on an ideal model, density functional theory calculations reveal that doping Fe–N4 can significantly enhance the anharmonicity of carbon-based materials and thus reduce the lattice thermal conductivity by more than 10 times. This work presents a facile and low-cost method for synthesizing carbon aerogel with single-atom doping for promising applications in thermal insulation.

Luminescent Water-Dispersible Nanoparticles Engineered from Copper(I) Halide Cluster Core and P,N-Ligand with an Optimal Balance between Stability and ROS Generation

The present work introduces the solvent exchange procedure as a route for conversion of the Cu4I4L2 complex, where the Cu4I4 cluster core is coordinated with two P,N-ligands (L), into an aqueous colloid. The analysis of both colloidal and supernatant phases revealed some losses in CuI going from the initial Cu4I4L2 complex to Cu2I2L3-based nanoparticles. The comparative analysis of IR, 31P NMR spectroscopy, ESI mass-spectrometry and luminescence data argued for a contribution of the “butterfly”-like structures of the Cu2I2 cluster core to Cu2I2L3-based nanoparticles, although the amorphous nature of the latter restricted structure evaluation from the PXRD data. The green luminescence of the colloids revealed their chemical stability under pH variations in the solutions of some amino acids and peptides, and to specify the temperature and concentration conditions triggering the oxidative degradation of the nanoparticles. The spin trap-facilitated ESR study indicated that the oxidative transformations were followed by the generation of reactive oxygen species (ROS). The physiological temperature level (310 K) enhanced the ROS generation by nanoparticles, but the ROS level was suppressed in the solution of GSH at pH = 7.0. The cytotoxicity of nanoparticles was evaluated in the M-HeLa cell line and is discussed in correlation with their cell internalization and intracellular oxidative transformations.

A simple and versatile strategy for sensitive SIDA-UHPLC-MS/MS analysis of Alternaria toxins in olive oil

Alternaria toxins are naturally occurring contaminants found in natural products. Given the prevalence of Alternaria toxins and the complexity of oil-rich matrices, achieving ultra-trace analysis has become a daunting task. A new sample pretreatment technique, i.e., cold-induced liquid-liquid microextraction combined with serially-coupled-columns for SIDA-UHPLC-MS/MS, was developed and reported for the first time. Theoretical and experimental investigations on the mechanism and key parameters revealed that the proposed method achieved simultaneous purification and enrichment in one-step sample extraction with a superior limit of quantitation (0.15–1.5 μg kg−1), without further sample manipulation, such as fat removal or solvent exchange procedures prior to LC-MS. The method was validated taking into consideration EU guidelines and showed acceptable linearity (r ≥ 0.9991), accuracy with recoveries between 75 and 114% and precision with RSD≤9.7% for all of the analytes studied. It was successfully applied to the analysis of twenty samples sourced from the Mediterranean region in order to gain first insights into Alternaria toxins contaminations in olive oils. This technical approach is well suited for large-scale studies in a high-throughput and cost-effective quality assurance laboratory environments, and it has the potential to detect ultra-trace levels of toxins in complex samples, which may lead to the development of new and sustainable sample preparation procedures.

Role of PSS-based assemblies in stabilization of Eu and Sm luminescent complexes and their thermoresponsive luminescence

The present work introduces self-assembled polystyrenesulfonate (PSS) molecules as soft nanocapsules for incorporation of Eu3+-Sm3+ complexes by the solvent exchange procedure. The high levels of Eu3+- and Sm3+-luminescence of the complexes derives from the ligand-to-metal energy transfer, in turn, resulted from the complex formation of Eu3+and Sm3+ ions with the three recently synthesized cyclophanic 1,3-diketones. The structural features of the ligands are optimized for the high thermal sensitivity of Eu3+- luminescence in DMF solutions. The PSS-nanocapsules (∼100 nm) provide both colloid and chemical stabilization of the ultrasmall (3–5 nm) nanoprecipitates of the complexes, although their luminescence spectra patterns and excited state lifetimes differ from the values measured for the complexes in DMF solutions. The specific concentration ratio of the Eu3+-Sm3+ complexes in the DMF solutions allows to tune the intensity ratio of the luminescence bands at 612 and 650 nm in the heterometallic Eu3+-Sm3+ colloids. The thermal sensitivity of the Eu3+- and Sm3+-luminescence of the complexes derives from the static quenching both in PSS-colloids and in DMF solutions, while the thermo-induced dynamic quenching of the luminescence is significant only in DMF solutions. The reversibility of thermo-induced luminescence changes of the Eu3+-Sm3+ colloids is demonstrated by six heating-cooling cycles. The DLS measurements before and after the six cycles reveal the invariance of the PSS-based capsule as the prerequisite for the recyclability of the temperature monitoring through the ratio of Eu3+-to- Sm3+ luminescence.

Monolithic Al2O3 Xerogels with Hierarchical Meso‐/Macropore System as Catalyst Supports for Methanation of CO2

AbstractCylindrical, cm‐sized monolithic Al2O3 xerogels with hierarchical meso‐/macropore system were prepared by sol‐gel synthesis. The influence of both solvent exchange and drying on monolith stability and the resulting pore system was studied following mass and volume of the monolith as well as by porosimetry and electron microscopy. Crack‐free drying of the monoliths requires a proper management of drying stress. This is achieved by adjusting the drying rate and solvent exchange procedure applied to the intermediate lyogels. Moreover, mainly through differences in capillary pressure, changing the pore fluid allows an adjustment of the mesopore width from 7.6 nm to 10.5 nm. Neither solvent exchange nor drying affect the macropores, the width of which stays at 1.5 μm. Finally, CO2 methanation over Ni‐impregnated Al2O3 monoliths reveals CO2 conversion and CH4 selectivity comparable to an industrial Ni/Al2O3 benchmark catalyst.

Synthesis of Lignosulfonate based Nanocarriers for the Delivery of Agrochemicals

Aims: The study's objective is to develop lignosulfonate-based nanocarriers as a UV protectant for agrochemical delivery
 Place and Duration of Study: Department of Nano Science & Technology, Tamil Nadu Agricultural University, Coimbatore. The research was carried out between March 2021 and January 2022.
 Methodology: We demonstrate a straightforward approach for the solvent – anti-solvent conversion of lignosulfonate macromolecules from black liquor derived from the paper pulping industry to nanocarriers. Due to the amphiphilic nature of lignin, nanoparticles are generated by self-assembly. To create lignin nanoparticles, a drop-by-drop solvent exchange approach has been used. The lignosulfonate solution was prepared using solvents such as ethanol and tetrahydrofuran, and then water was added as an antisolvent, resulting in the creation of nanoparticles by self-assembly. The hydrophobic portion of lignin creates the particle's core, while the hydrophilic hydroxyl groups form the particle's shell. The size and stability of nanoparticles were determined using dynamic light scattering, and the form and size of the systems were imaged using scanning electron microscopy. The functional groups of the nanoparticles were determined using Fourier transform infrared spectroscopy.
 Results: Solvent tetrahydrofuran generated uniform and spherical lignosulfonate nanoparticles than the solvent ethanol employed in the solvent exchange procedure. When ethanol and cetyl trimethyl ammonium bromide were used as solvent and surfactant, respectively, the size of lignosulfonate nanoparticles was smaller (270±31.9nm). However, the stability of nanocarrier systems was unaffected by the solvent used, with polydispersity index values of 0.435±0.003 and 0.401±0.028 for tetrahydrofuran and ethanol solvents, respectively. The existence of a distinctive peak at 526 and 609 cm-1 in the infrared spectrum corresponding to sulfonic stretching indicated the presence of lignosulfonate in the carrier systems.
 Conclusion: Lignosulfonate-based nanocarrier systems were developed using the solvent exchange method. However, the nanocarrier systems are to be validated to assess the bioefficacy of active molecules.

Enhanced hydrophobicity of modified ZIF-71 metal-organic framework for biofuel purification

Hydrophobic materials are desirable for biofuel purification applications. In this work, the atomic substitution of Cl atom with Br atom in the imidazole organic linker was carried out to produce a more hydrophobic ZIF-71, named ZIF-71(ClBr) and ZIF-71(ClBr)-SE for the material with an additional solvent exchange procedure. The physicochemical characterization revealed that ZIF-71(ClBr) and ZIF-71(ClBr)-SE are isostructural to ZIF-71, have a high surface area (769 and 969 m2/g), and are hydrophobic (126 and 130° water contact angle). As a proof of concept, D4 siloxane adsorption capacity onto ZIF-71(ClBr) and ZIF-71(ClBr)-SE was estimated (1.76 and 2.66 mg/g, respectively). Furthermore, a superior adsorption capacity was obtained when ZIF-71(ClBr)-SE was used due to its higher hydrophobic nature, and similar results were obtained with ZIF-8, used as a frame of reference. Therefore, the high surface area and the hydrophobic nature of ZIF-71(ClBr)-SE make it compelling material for biofuel purification applications.

Delivery of DNA into Human Cells by Functionalized Lignin Nanoparticles.

Lignin is an aromatic plant cell wall polymer that is generated in large quantities as a low-value by-product by the pulp and paper industry and by biorefineries that produce renewable fuels and chemicals from plant biomass. Lignin structure varies among plant species and as a function of the method used for its extraction from plant biomass. We first explored the impact of this variation on the physico-chemical properties of lignin nanoparticles (LNPs) produced via a solvent exchange procedure and then examined whether LNPs produced from industrial sources of lignin could be used as delivery vehicles for DNA. Spherical LNPs were formed from birch and wheat BioLignin™ and from poplar thioglycolic acid lignin after dissolving the lignin in tetrahydrofuran (THF) and dialyzing it against water. Dynamic light scattering indicated that the diameter of these LNPs was dependent on the initial concentration of the lignin, while electrophoretic light scattering indicated that the LNPs had a negative zeta potential, which became less negative as the diameter increased. The dynamics of LNP formation as a function of the initial lignin concentration varied as a function of the source of the lignin, as did the absolute value of the zeta potential. After coating the LNPs with cationic poly-l-lysine, an electrophoretic mobility shift assay indicated that DNA could adsorb to LNPs. Upon transfection of human A549 lung carcinoma basal epithelial cells with functionalized LNPs carrying plasmid DNA encoding the enhanced green fluorescent protein (eGFP), green foci were observed under the microscope, and the presence of eGFP in the transfected cells was confirmed by ELISA. The low cytotoxicity of these LNPs and the ability to tailor diameter and zeta potential make these LNPs of interest for future gene therapy applications.

Rational design of efficient nanosensor for glyphosate and temperature out of terbium complexes with 1,3-diketone calix[4]arenes

The temperature and substrate dependent luminescence of terbium complexes with calix[4]arene derivatives makes them promising building blocks of nanosensors. Thus, calix[4]arene 1,3-diketones in 1,3-alternate and cone isomeric forms bearing buthyl, dodecyl, nonyl and bromine substituents are introduced as ligands forming luminescent Tb3+ complexes in basified DMF solutions. The structure variation of the ligands allows to highlight buthyl-substituted derivative of calix[4]arene 1,3-diketone in 1,3-alternate isomeric form as the optimal structure. The detailed studies of the complex stoichiometry by means of UV-Vis and H1 NMR diffusion spectroscopy methods reveal 2:2 stoichiometry as the main for the calix[4]arene 1,3-diketones in 1,3-alternate isomeric form. The predominance of 2:2 over 1:1 and 1:2 (Tb:L) complex stoichiometries for the buthyl-substituted ligand was confirmed by comparison of the quantum chemically calculated thermochemical parameters of their complex formation. However, the 2:2 complex formation is either restricted for their dodecyl-substituted derivative or interferes with the 1:2 stoichiometry for the bromo-substituted counterpart. The conversion of the Tb3+ complexes from the DMF solutions to the PSS-stabilized colloids through the solvent-exchange procedure reveals the unfavorable effect of the nonyl- and dodecyl-substituted ligands on aggregation behavior of the colloids. Thus, 2:2 terbium complex with buthyl-substituted ligand in 1,3-alternate isomeric form is the optimal basis for production of the luminescent PSS-colloids with high colloid stability. The Tb3+- luminescence of the colloids exhibit the enhanced sensitivity to both environmental pollutant glyphosate with LOD = 1.97 nM and temperature changes within the physiological temperature range with SI = −4.67 K-% at 323 K.

Hierarchical build-up of bio-based nanofibrous materials with tunable metal–organic framework biofunctionality

Multifunctional, light-weight, responsive materials show promise in a range of applications including soft robotics, therapeutic delivery, advanced diagnostics and charge storage. This paper presents a novel, scalable, efficient and sustainable approach for the preparation of cellulose nanofibril-based aerogels via a facile ice-templating, solvent exchange and air-drying procedure, which could replace existing inefficient drying processes. These ambient-dried aerogels (∼99% porosity) exhibit a high specific compressive modulus (26.8 ± 6.1 kPa m3 kg−1, approaching equivalence of carbon-nanotube-reinforced aerogels), wet stability and shape recovery (80–90%), favorable specific surface area (90 m2 g−1) and tunable densities (2–20 kg m−3). The aerogels provide an ideal nanofibrillar substrate for in-situ growth of metal–organic frameworks (MOFs), via co-assembly of MOF precursors with proteins in aqueous solutions. The resulting hybrid aerogels show a nine-fold increase in surface area (810 m2g−1), with preserved wet stability and additional protein biofunctionality. The hybrid aerogels facilitate a pH-controlled release of immobilized proteins, following a concomitant disassembly of the surface grown MOFs, demonstrating their use in controlled delivery systems. The colorimetric protein binding assay of the biofunctionalized hybrid aerogel also demonstrates the potential of the material as a novel 3D bioassay platform, which could potentially be an alternative to plate-based enzyme-linked immunosorbent assay.

White Light Emitting CdS Quantum Dot Devices Coated with Layers of Graphene Carbon Quantum Dots

AbstractCadmium sulfide quantum dots (CdS QDs) are semiconductor nanoparticles having sizes in the order of nanometers. They are materials that have outstanding properties for down conversion applications. These nanostructures have been used in the fabrication of white light emitting diodes (WLEDs) in the last years. However, inhomogeneous deposition of CdS QD conversion materials allows unwanted UV light escape. In addition, low efficiency due to strong self-quenching effect, incompatibility between CdS QD solution/crystal polyester resin matrix and reabsorption are common problems that need to be solved. In this work, we try to address the incompatibility between the CdS QD solution/crystal polyester resin matrix by using a solvent exchange procedure. To block the unwanted UV-light escape, we coated our devices with a mixture of graphene carbon quantum dot (GCQD) solution/crystal polyester resin matrix. The QDs and the WLED prototypes were characterized by absorption and photoluminescence (PL) spectroscopy. The QDs embedded in the matrix shown a good homogeneous dispersion. On the other hand, the mixture shown a rapid solidification. These facts indicate a good compatibility between the CdS QDs and the crystal polyester resin. We also observed a considerable reduction of unwanted near UV-light. White light emission from WLED devices with common crystal polyester resin and low-cost materials has been achieved.

Production of biodegradable superabsorbent aerogels using a supercritical CO2 assisted drying

Superabsorbent polymers (SAPs) are organic materials possessing high capacity to absorb and retain large volumes of water, saline and physiological solutions (at least 10–20 times their weight). The most commonly used SAPs are acrylated-based polymers that are not biodegradable or recyclable. To overcome these limits, carboxymethylcellulose (CMC) with hydroxyethylcellulose (HEC) hydrogels were synthetized in this work and dried using a supercritical assisted process at 200 bar and 45 °C. The solvent exchange procedure influenced the final aerogel morphology and, thus, the aerogel swelling ratio (SR). A solvent exchange starting from 50 % v/v ethanol, preserved the native gel nanofibrous morphology, producing a SR up to 20 times larger than the ones reported in the literature using the same process, corresponding to a water uptake larger than 500 times the weight of the dried aerogel.

Light-driven micron-scale 3D hydrogel actuator produced by two-photon polymerization microfabrication

Light-driven micro/nano-actuators are one of the most important topics in the biomedical micro-electromechanical systems (MEMS) field. Currently, their development is hampered due to the difficulties in designing and fabricating biocompatible light-driven microactuators with the dimensions less than one hundred micrometres and a response time in the order of seconds. In this work, gel photoresists were prepared by embedding photothermal surface-modified Fe3O4 nanoparticles (NPs) into a mixture that included a photoinitiator, photosensitizer, monomers, crosslinkers and solvents. Macroscopic poly(N-isopropylacrylamide) (PNIPAM)/nano-Fe3O4 hydrogels were prepared by ultraviolet photopolymerization of gel photoresists, which showed good temperature-responsive volume changes and light-triggered bending deformation. Then the two-photon polymerization (TPP) microfabrication properties of gel photoresists with 0, 0.48 and 0.95 wt% Fe3O4 NPs were investigated in detail. Importantly, after the TPP microfabrication and subsequent solvent-exchange procedure, a double-armed near-infrared (NIR)-light-driven three-dimensional (3D) hydrogel microcantilever with a size of ∼26 μm was successfully fabricated. The hydrogel microactuator had a fast response time of ∼0.033 s in water under NIR radiation and showed good reversibility. Furthermore, the distance between the two arms of the hydrogel microcantilever could be manipulated by controlling the laser focus and incident laser power.

Geminal Coordinatively Unsaturated Sites on MOF-808 for the Selective Uptake of Phenolics from a Real Bio-Oil Mixture.

The capping formate anions of the metal-organic framework (MOF) zirconium benzene-1,3,5-tricarboxylate (MOF-808) were removed by a solvent exchange procedure, resulting in a formate-free MOF-808 sample containing "geminal" defects consisting of six coordinatively unsaturated sites (CUSs) on each of the Zr6 nodes. Adsorption experiments with this material showed that the uptake of 4-methylguaiacol from a bio-oil mixture was proportional to the number of defects and amounted to one mole adsorbed per mole of zirconium. The selective uptake behavior of MOF-808 towards phenolic compounds was further evident from competitive adsorption experiments between furfuryl alcohol and 4-methylguaiacol as well as from the excellent (20 wt % for phenolic compounds and <7 wt % for other compounds) uptake performance for real bio-oil mixtures containing a large concentration and diversity of molecules.

High Throughput Quantification of Quaternary Ammonium Cations in Food Simulants by Flow-Injection Mass Spectrometry.

Background: A flow-injection MS (FI/MS) method was evaluated for the quantitation of quaternary ammonium cations (QACs) in simple food simulants. Methods: The calibration standard was dimethyldioctadecyl ammonium ion (C18-C18), and the internal standard was benzyldimethylhexadecyl (BDMHD) ammonium ion. Calibration standards based on the C18-C18 ion were prepared in ethanol with a range of 5 to 500 ppb and contained 100 ppb BDMHD. The mobile phase was 90 + 10 (v/v) acetonitrile-5 mM aqueous ammonium acetate and flowed directly into an electrospray source of the mass spectrometer. Detection was accomplished by single ion recording (SIR) in positive mode. Results: Calibration curves were linear with coefficients of determination above 0.995, and the LOQ was 5 ppb. Recoveries of four QACs derived from Arquad 2HT-75, a commercially available surfactant, were measured in common food simulants: ethanol, water, 10% (v/v) ethanol in water, and 3% (v/v) aqueous acetic acid. A solvent exchange procedure was employed for the three aqueous solvents, which included complete evaporation of the sample followed by reconstitution in ethanol prior to injection. The solvent exchange method minimized losses because of QAC adsorption on glass surfaces. Recoveries ranged from 74.4 ± 4.0 to 106.7 ± 6.6% for the two most abundant Arquad 2HT-75 component cations, dimethyldioctadecyl ammonium and dimethyloctadecyl-hexadecyl ammonium. Conclusions: This method is suitable to quantify trace levels of QACs in food simulants as part of exposure evaluations related to their use in emerging food contact materials.

One-pot preparation of bi-functional cellulose nanofibrils

Herein, we present a route to obtain bi-functional cellulose nanofibrils (CNF) by a one-pot approach using an already established functionalisation route, carboxymethylation, to which a subsequent functionalisation step, allylation or alkynation, has been added in the same reaction pot, eliminating the need of solvent exchange procedures. The total charge of the fibres and the total surface charge of the nanofibrils were determined by conductometric and polyelectrolyte titration, respectively. Furthermore, the allyl and alkyne functionalised cellulose were reacted with methyl 3-mercaptopropionate and azide-functionalised disperse red, respectively, to estimate the degree of functionalisation. The samples were further assessed by XPS and FT-IR. Physical characteristics were evaluated by CP/MAS 13C-NMR, XRD, AFM and DLS. This new approach of obtaining bi-functionalised CNF allows for a facile and rapid functionalisation of CNF where chemical handles can easily be attached and used for further modification of the fibrils.Graphical abstract

Laser-Induced CO2 Generation from Gold Nanorod-Containing Poly(propylene carbonate)-Based Block Polymer Micelles for Ultrasound Contrast Enhancement.

Poly(propylene carbonate) (PPC) decomposes at high temperature to release CO2. This CO2-generation temperature of PPC can be reduced down to less than 80 °C with the aid of a photoacid generator (PAG). In the present work, we demonstrate that using an additional helper component, surface plasmonic gold nanorods (GNRs), the PPC degradation reaction can also be initiated by infrared (IR) irradiation. For this purpose, a PPC-containing nanoparticle formulation was developed in which PPC-based amphiphilic block copolymers (BCPs), poly(poly(ethylene glycol) methacrylate- b-propylene carbonate- b-poly(ethylene glycol) methacrylate) (PPEGMA-PPC-PPEGMA), were self-assembled with GNRs and PAG molecules via solvent exchange. Under IR irradiation, GNRs produce heat that can cause PPC to decompose into CO2, and PAG (after UV pretreatment) catalyzes this PPC degradation process. Two PPEGMA-PPC-PPEGMA materials were used for this study: PPEGMA7.3K-PPC5.6K-PPEGMA7.3K ("G7C6G7") and PPEGMA2.1K-PPC5.6K-PPEGMA2.1K ("G2C6G2"). Addition of CTAB-coated GNRs dispersed in water to a G2C6G2 solution in DMF produced individually G2C6G2-encapsulated GNRs, whereas the same solvent exchange procedure resulted in the formation of polymer-coated GNR clusters when G7C6G7 was used as the encapsulating material. GNR/G2C6G2 NPs exhibited a surface plasmon resonance peak at 697 nm. The clustered morphology of G7C6G7-encapsulated GNRs caused a blue shift of the absorbance maximum to 511 nm. As a consequence, GNR/G2C6G2 NPs showed a greater absorbance/heat generation rate under IR irradiation than did GNR/G7C6G7 NPs. The IR-induced CO2 generation rate was about 4.2 times higher with the GNR/G2C6G2+PAG sample than that with the GNR/G7C6G7+PAG sample. Both GNR/G7C6G7+PAG and GNR/G2C6G2+PAG systems produced ultrasound contrast enhancement effects under continuous exposure to IR light for >20 min; contrast enhancement was more spatially uniform for the GNR/G2C6G2+PAG sample. These results support the potential utility of PPC as a CO2-generating contrast agent in ultrasound imaging applications.