Reversible Addition-fragmentation Chain Transfer Research Articles

Unleashing the Power of PET-RAFT Polymerization: Journey from Porphyrin-Based Photocatalysts to Combinatorial Technologies and Advanced Bioapplications.

The emergence of photoinduced energy/electron transfer-reversible addition-fragmentation chain transfer polymerization (PET-RAFT) not only revolutionized the field of photopolymerization but also accelerated the development of porphyrin-based photocatalysts and their analogues. The continual expansion of the monomer family compatible with PET-RAFT polymerization enhances the range of light radiation that can be harnessed, providing increased flexibility in polymerization processes. Furthermore, the versatility of PET-RAFT polymerization extends beyond its inherent capabilities, enabling its integration with various technologies in diverse fields. This integration holds considerable promise for the advancement of biomaterials with satisfactory bioapplications. As researchers delve deeper into the possibilities afforded by PET-RAFT polymerization, the collaborative efforts of individuals from diverse disciplines will prove invaluable in unleashing its full potential. This Review presents a concise introduction to the fundamental principles of PET-RAFT, outlines the progress in photocatalyst development, highlights its primary applications, and offers insights for future advancements in this technique, paving the way for exciting innovations and applications.

Modular design of cyclic peptide – polymer conjugate nanotubes for delivery and tunable release of anti-cancer drug compounds

High aspect-ratio nanomaterials have recently emerged as promising drug delivery vehicles due to evidence of strong cellular association and prolonged in vivo circulation times. Cyclic peptide - polymer conjugate nanotubes are excellent candidates due to their elongated morphology, their supramolecular composition and high degree of pliability due to the versatility in manipulating amino acid sequence and polymer type. In this work, we explore the use of a nanotube structure on which a potent anti-cancer drug, camptothecin, is attached alongside hydrophilic or amphiphilic RAFT polymers, which shield the cargo. We show that subtle modifications to the cleavable linker type and polymer architecture have a dramatic influence over the rate of drug release in biological conditions. In vitro studies revealed that multiple cancer cell lines in 2D and 3D models responded effectively to the nanotube treatment, and analogous fluorescently labelled materials revealed key mechanistic information regarding the degree of cellular uptake and intracellular fate. Importantly, the ability to instruct specific drug release profiles indicates a potential for these nanomaterials as vectors which can provide sustained drug concentrations for a maximal therapeutic effect.

Antioxidant Polymers with Phenolic Pendants for the Mitigation of Cellular Oxidative Stress.

Overproduction of reactive oxygen species (ROS) in cells is a major health concern as it may lead to various diseases through oxidative damage of biomolecules. Commonly used traditional small molecular antioxidants (polyphenols, carotenoids, vitamins, etc.) have inadequate efficacy in lowering excessive levels of ROS due to their poor aqueous solubility and bioavailability. In response to the widespread occurrence of antioxidant polyphenols in various biorenewable resources, we aimed to develop water-soluble antioxidant polymers with side chain phenolic pendants. Four different types of copolymers (P1-P4) containing phenyl rings with different numbers of hydroxy (-OH) substituents (0: phenylalanine, 1: tyrosyl, 2: catechol, or 3: gallol) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization with a desired molar mass (8500-10000 g/mol) and a narrow dispersity (Đ ≤ 1.3). After successful characterizations of P1-P4, their in vitro antioxidant properties were analyzed by different methods, including 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+), 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl (TMB), and β-carotene (βC) assays. Our results revealed that the gallol pendant polymers can effectively scavenge ROS. Furthermore, electron paramagnetic resonance (EPR) spectroscopy with DPPH• also confirmed the radical quenching ability of the synthesized polymers. The gallol pendant polymers, at a well-tolerated concentration, could effectively penetrate the macrophage cells and restore the H2O2-induced ROS to the basal level. Overall, the present approach demonstrates the efficacy of water-soluble antioxidant polymers with gallol pendants toward the mitigation of cellular oxidative stress.

Development of Biocompatible Digital Light Processing Resins for Additive Manufacturing Using Visible Light-Induced RAFT Polymerization.

Patients with bone diseases often experience increased bone fragility. When bone injuries exceed the body's natural healing capacity, they become significant obstacles. The global rise in the aging population and the escalating obesity pandemic are anticipated to lead to a notable increase in acute bone injuries in the coming years. Our research developed a novel DLP resin for 3D printing, utilizing poly(ethylene glycol diacrylate) (PEGDA) and various monomers through the PET-RAFT polymerization method. To enhance the performance of bone scaffolds, triply periodic minimal surfaces (TPMS) were incorporated into the printed structure, promoting porosity and pore interconnectivity without reducing the mechanical resistance of the printed piece. The gyroid TPMS structure was the one that showed the highest mechanical resistance (0.94 ± 0.117 and 1.66 ± 0.240 MPa) for both variants of resin composition. Additionally, bioactive particles were introduced to enhance the material's biocompatibility, showcasing the potential for incorporating active compounds for specific applications. The inclusion of bioceramic particles produces an increase of 13% in bioactivity signal for osteogenic differentiation (alkaline phosphatase essay) compared to that of control resins. Our findings highlight the substantial improvement in printing precision and resolution achieved by including the photoabsorber, Rose Bengal, in the synthesized resin. This enhancement allows for creating intricately detailed and accurately defined 3D-printed parts. Furthermore, the TPMS gyroid structure significantly enhances the material's mechanical resistance, while including bioactive compounds significantly boosts the polymeric resin's biocompatibility and bioactivity (osteogenic differentiation).

Injectable biocompatible RAFT mediated nitroxide nanogels: A robust ROS-reduction antioxidant approach

This work introduces novel nitroxide-based nanogels (NGs) crafted through controlled RAFT (Reversible Addition Fragmentation chain Transfer) polymerization, showcasing over 85% improved shelf-life compared to native superoxide dismutase (SOD) enzymes. These 30–40 nm NGs hold great promise for injectable delivery, effectively reducing foam cell formation and displaying potent antioxidant behavior against various reactive oxygen species (ROS), revolutionizing antioxidant therapy. Featuring a meticulously designed core-shell structure via precise RAFT polymerization, these NGs mimic SOD enzymatic activity with nitroxide-based antioxidants, providing unprecedented defense against ROS. Combining methacrylated 2,2,6,6-Tetramethyl-4-piperidyl methacrylate (PMA) and Glycidyl methacrylate (GMA) monomers with precisely synthesized nitroxyl radicals results in exceptional properties. Validated through comprehensive analytical methods, these NGs exhibit remarkable stability, halting foam cell formation even at high concentrations, and demonstrate notable biocompatibility. Their ability to protect low density lipoprotein (LDL) from oxidation for up to a month positions them at the forefront of combating cardiovascular diseases, especially atherosclerosis. This study pioneers injectable antioxidant therapy, offering an innovative approach to cardiovascular ailments. Targeting narrow plaques signifies a promising intervention, reshaping cardiovascular disease treatments. It highlights the potential of advanced drug delivery in biomedicine, promising more effective cardiovascular disease treatments.

Effect of Temperature, Oil Type, and Copolymer Concentration on the Long-Term Stability of Oil-in-Water Pickering Nanoemulsions Prepared Using Diblock Copolymer Nanoparticles.

A poly(glycerol monomethacrylate) (PGMA) precursor was chain-extended with 2,2,2-trifluoroethyl methacrylate (TFEMA) via reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerization. Transmission electron microscopy (TEM) studies confirmed the formation of well-defined PGMA52-PTFEMA50 spherical nanoparticles, while dynamic light scattering (DLS) studies indicated a z-average diameter of 26 ± 6 nm. These sterically stabilized diblock copolymer nanoparticles were used as emulsifiers to prepare oil-in-water Pickering nanoemulsions: either n-dodecane or squalane was added to an aqueous dispersion of nanoparticles, followed by high-shear homogenization and high-pressure microfluidization. The Pickering nature of such nanoemulsion droplets was confirmed via cryo-transmission electron microscopy (cryo-TEM). The long-term stability of such Pickering nanoemulsions was evaluated by analytical centrifugation over a four-week period. The n-dodecane droplets grew in size significantly faster than squalane droplets: this is attributed to the higher aqueous solubility of the former oil, which promotes Ostwald ripening. The effect of adding various amounts of squalane to the n-dodecane droplet phase prior to emulsification was also explored. The addition of up to 40% (v/v) squalane led to more stable nanoemulsions, as judged by analytical centrifugation. The nanoparticle adsorption efficiency at the n-dodecane-water interface was assessed by gel permeation chromatography when using nanoparticle concentrations of 4.0, 7.0, or 10% w/w. Increasing the nanoparticle concentration not only produced smaller droplets but also reduced the adsorption efficiency, as confirmed by TEM studies. Furthermore, the effect of varying the nanoparticle concentration (2.5, 5.0, or 10% w/w) on the long-term stability of n-dodecane-in-water Pickering nanoemulsions was explored over a four-week period. Nanoemulsions prepared at higher nanoparticle concentrations were more unstable and exhibited a faster rate of Ostwald ripening. The nanoparticle adsorption efficiency was monitored for an aging nanoemulsion prepared at a copolymer concentration of 2.5% w/w. As the droplets ripened over time, the adsorption efficiency remained constant (∼97%). This suggests that nanoparticles desorbed from the shrinking smaller droplets and then readsorbed onto larger droplets over time. Finally, the effect of temperature on the stability of Pickering nanoemulsions was examined. Storing these Pickering nanoemulsions at elevated temperatures led to faster rates of Ostwald ripening, as expected.

Exploring Functional Polymers in the Synthesis of Luminescent ZnO Quantum Dots for the Detection of Cr6+, Fe2+, and Cu2.

The main aim of this work is to demonstrate that well-defined methacrylate-based copolymers with oligoethylene glycol side chains and functional groups such as thiol and glycidyl, obtained by photo-initiated reversible addition-fragmentation chain transfer (RAFT) in ethanol, are highly suitable as templates in the synthesis and protection of ZnO quantum dots (ZnO QDs) with remarkable photoluminescent properties. While the affinity of thiol groups to metallic surfaces is well established, their interaction with metal oxides has received less scrutiny. Furthermore, under basic conditions, glycidyl groups could react with hydroxyl groups on the surface of ZnO, representing another strategy for hybrid synthesis. The size and crystalline morphology of the resulting hybrids were assessed using DLS, TEM, and XRD, indicating that both polymers, even with a low proportion of functional groups (5% mol) are appropriate as templates and ligands for ZnO QDs synthesis. Notably, thiol-containing polymers yield hybrids with ZnO featuring excellent quantum yield (up to 52%), while polymers with glycidyl groups require combination with the organosilane aminopropyl triethoxysilane (APTES) to achieve optimal results. In both cases, these hybrids exhibited robust stability in both ethanol and aqueous environments. Beyond fundamental research, due to the remarkable photoluminescent properties and affordability, these hybrid ZnO QDs are expected to have potential applications in biotechnology and green science; in particular, in this study, we examined their use in the detection of environmental contaminants like Fe2+, Cr6+, and Cu2+. Specifically, the limit of detection achieved at 1.13 µM for the highly toxic Cr6+ underscores the significant sensing capabilities of the hybrids.

A new method for synthesis of modified cellulose‐graft‐poly(acrylic acid) copolymer using 4‐cyano‐4‐[(phenylcarbothioyl)solfanyl]pentanoic acid to serve as RAFT agent

AbstractIn this study, cellulose was first treated with 4‐cyano‐4‐((phenyl carbonothioyl)solfanyl) pentanoic acid to serve as the reversible addition‐fragmentation chain transfer polymerization (RAFT) agent, then the controlled grafting polymerization of acrylic acid was successfully performed. A well‐defined, cellulose‐graft‐acrylic acid copolymer (Cell‐g‐PAA), has been prepared by RAFT polymerization technique using three different approaches: RAFT agent was prepared by substitution of dithiobenzoate magnesium bromide with 4,4'‐azobis(4‐cyanopentanoic acid) in ethyl acetate as a solvent, mediated cellulose (Cell) block as the macromolecular Cell‐RAFT agent and (cellulose‐co‐acrylic acid) copolymer with alternating sequence. The resulting (Cell‐RAFT) for “living” free radical polymerization was then heated in the adjacent acrylic acid monomer for the development of the controlled graft copolymer onto cellulose. The structures of the intermediate, graft copolymer were investigated by FT‐IR, DSC, 1H NMR, scanning electron microscopy, and thermo gravimetric. The results demonstrate that the preparation of graft copolymers was successfully confirmed. This approach would provide an extensive classification of molecular designs to obtain modern types of tailored hybrid materials derived from natural polysaccharides and synthetic polymers. Also, using a macro‐initiator is an excellent method for synthesizing new materials.

Superior antibacterial surfaces using hydrophilic, poly(MPC) and poly(mOEGMA) free chains of amphiphilic block copolymer for sustainable use

Surface modification of electrically neutral hydrophilic polymers is one of the most promising methods for preventing biofouling and biological contamination by proteins and bacteria. Surface modification of inorganic materials such as silica-based glass can render them more durable and thus help in achieving the sustainable development goals. This study reports a novel method for the simple and effective surface modification of glass surfaces with amphiphilic block copolymers possessing the silane coupling segment composed of 3-(methacryloyloxy)propyltris (trimethylsilyloxy) silane and 3-methacryloxypropyltrimethoxysilane. The ability of hydrophilic segments composed of either 2-methacryloyloxyethyl phosphorylcholine (MPC) or poly(ethylene glycol) methyl ether methacrylate (mOEGMA) to prevent bacterial adhesion was investigated. The target block copolymers were prepared by reversible addition-fragmentation chain transfer polymerization and the monomer units of the hydrophilic segments were controlled to be either 120 or 160. The polymers were modified on the substrate by dip-coating. Contact angle measurements indicated that the block copolymer with the PMPC hydrophilic segment formed a hydrophilic surface without pre-hydration, while those with the PmOEGMA hydrophilic segment-coated surface became hydrophilic upon immersion in water. The block copolymer-coated surfaces decreased S. aureus adhesion, and a significant reduction was observed with the MPC-type block copolymer. The following surface design guidelines were thus concluded: (1) the block copolymer is superior to the random copolymer and (2) increasing the hydrophilic segment length further decreases bacterial adhesion.

Tuning the Mechanical Properties of 3D‐printed Objects by the RAFT Process: From Chain‐Growth to Step‐Growth

AbstractPhotoinduced 3D printing based on the reversible addition‐fragmentation chain transfer (RAFT) process has emerged as a robust method for creating diverse functional materials. However, achieving precise control over the mechanical properties of these printed objects remains a critical challenge for practical application. Here, we demonstrated a RAFT step‐growth polymerization of a bifunctional xanthate and bifunctional vinyl acetate. Additionally, we demonstrated photoinduced 3D printing through RAFT step‐growth polymerization with a tetrafunctional xanthate and a bifunctional vinyl acetate. By adjusting the molar ratio of the components in the printing resins, we finely tuned the polymerization mechanism from step‐growth to chain‐growth. This adjustment resulted in a remarkable range of tunable Young's moduli, ranging from 7.6 MPa to 997.1 MPa. Moreover, post‐functionalization and polymer welding of the printed objects with varying mechanical properties opens up a promising way to produce tailor‐made materials with specific and tunable properties.

Tuning the Mechanical Properties of 3D-printed Objects by the RAFT Process: From Chain-Growth to Step-Growth.

Photoinduced 3D printing based on the reversible addition-fragmentation chain transfer (RAFT) process has emerged as a robust method for creating diverse functional materials. However, achieving precise control over the mechanical properties of these printed objects remains a critical challenge for practical application. Here, we demonstrated a RAFT step-growth polymerization of a bifunctional xanthate and bifunctional vinyl acetate. Additionally, we demonstrated photoinduced 3D printing through RAFT step-growth polymerization with a tetrafunctional xanthate and a bifunctional vinyl acetate. By adjusting the molar ratio of the components in the printing resins, we finely tuned the polymerization mechanism from step-growth to chain-growth. This adjustment resulted in a remarkable range of tunable Young's moduli, ranging from 7.6 MPa to 997.1 MPa. Moreover, post-functionalization and polymer welding of the printed objects with varying mechanical properties opens up a promising way to produce tailor-made materials with specific and tunable properties.

Tunable Polymer Micelles as Template Directing Growth of MOFs Crystals in Surfactant‐Free Emulsion to Fabricate Chitosan‐Based Copolymer/ZIF‐8 Nanostructure

AbstractAn amphiphilic chitosan‐g‐poly N‐(3‐dimethylaminopropyl) methacrylamide (CS‐g‐PDMAPMA, CSP) was proposed and synthesized by reversible addition‐fragmentation chain transfer polymerization (RAFT), and further employed as emulsifier to construct a surfactant‐free emulsion. The morphology of micelles in surfactant‐free emulsion was regulated by adjusting the oil‐water ratio and concentration of amphiphilic copolymer. Subsequently, polymer micelles served as templates to direct the assembly of ZIF‐8 crystals in the surfactant‐free emulsion to fabricate polymer/ZIF‐8 composite materials (ZIF‐8@CSP) with various structures. Specifically, ZIF‐8@CSP with various architectures such as spheres, rods, cubes, leaf‐shaped flakes, cross‐flowers and wrinkled cubes were obtained by varying the concentration of CSP, the addition sequence of ZIF‐8 precursors and the ratio of oil‐water.

Organic Brønsted Acid-Catalyzed Stereoselective Cationic RAFT Polymerization: The Effect of RAFT Agents

Organic Brønsted Acid-Catalyzed Stereoselective Cationic RAFT Polymerization: The Effect of RAFT Agents

Polymer brush construction with interface-mediated RAFT polymerization technique for glutathione determination

Reactive polymeric thin films designed on solid surfaces have widespread applications in many fields involving the immobilization of biomolecules. Efficient and specific designs for biomolecule immobilization on polymer-modified solid surfaces are central to biosensor technologies such as protein and gene chips. Research areas related to the functionalization of surfaces include polymer brushes whose functionality is increased by the Diels-Alder (DA) reaction, which have been made usable as rewritable platforms with their thermal transformation properties and have found a lot of use, especially in biomolecule determination studies. Glutathione (GSH), one of the biomolecules, is found in in very high intracellular concentrations. It is the most important antioxidant molecule in the environment and its determination is a good indicator for us to obtain information about the status of the antioxidant defense mechanism in various diseases. When studies in were examined in detail, no study was found on the synthesis of polymer brushes with thiol functional groups covalently bonded to the silicon surface using the interfacial-mediated RAFT polymerization technique and their use in GSH adsorption. Therefore, in this study, to fill this gap in the literature, polymer brushes with thiol (SH) functional groups to be used in GSH adsorption were synthesized. Poly(furfurylmethacrylate) [poly(FMA)] brushes, formed by polymer chains covalently bonded to the silicon surface, were synthesized by interface-mediated RAFT polymerization. Then, by maleimide conjugation using hexylamine, polymeric brushes with thiol functional groups covalently bonded to the silicon surface which can be used in GSH adsorption were obtained for determination purposes. It is thought that the prepared polymeric brushes will find a wide application area for the determination of many new molecules, especially the determination of glutathione and will contribute to the literature.

Tunable self-assembly of lipid-based block polymeric micelles with temperature-sensitive poly(vinylcaprolactam) shell for effective anticancer drug delivery

Lipids, as naturally occurring biomolecules have emerged as promising carriers for delivering various therapeutic agents. However, only a few attempts have been made in terms of their applications as amphiphilic block copolymers for anticancer drug delivery. In this work, a biocompatible micellar drug delivery system with fatty acid-based polymer core and temperature-sensitive shell was developed. A series of amphiphilic block copolymers poly(vinyl stearate)/poly(vinyl laurate)-b-poly(N-vinylcaprolactam) (PVS/PVL-b-PNVCL) were synthesized via microwave-assisted reversible addition-fragmentation chain transfer polymerization in a controlled fashion. By varying the fatty acid type and hydrophilic/hydrophobic block lengths, the self-assembly behaviour of the block copolymer micelles proved to be highly tunable in terms of their morphology and particle size. Nile Red and hydrophobic anticancer drug doxorubicin (DOX) were effectively incorporated into the micelles, demonstrating high drug loading capacity, good serum stability, and temperature-dependent drug release characteristics of the polymeric micelles. In vitro studies using cell models revealed that blank PVS -b-PNVCL micelles are biocompatible with different cell lines, while DOX-loaded micelles were internalized into and accumulated in the cells, showing a high cytotoxic effect against HeLa cells. These findings suggest an opportunity for the development of safe and efficient lipid-based micellar system for smart drug delivery and cancer treatments.

Synthesis of a water‐soluble chain transfer agent and its application in gel dispersions

AbstractPre‐crosslinked gel particles, colloidal dispersion gels, and polymer microspheres are often used as profile‐controlling and flooding agents to displace residual crude oil from formations. The preparation process of these profile‐controlling and flooding agents is complicated. In order to simplify the preparation steps, a water‐soluble chain transfer (RAFT) agent, S,S′‐bis(2‐propionic acid) trithiocarbonate (PATTC), was synthesized, and then, hydrogel dispersions were prepared by one‐pot RAFT polymerization. The structure of PATTC was confirmed by infrared spectroscopy and nuclear magnetic resonance. The effects of reaction conditions on the viscosity and viscosity‐average molecular weight of hydrogel dispersions were explored, the rheology, viscoelasticity, particle size, temperature responsiveness, and salinity responsiveness of hydrogel dispersions were measured, and the seepage properties of hydrogel dispersions in porous medium were analyzed. The results show that at higher shear rates, the polyacrylamide gel dispersions exhibited Newtonian fluid characteristics. Viscoelasticity tests further confirmed that the polyacrylamide gel dispersions were successfully synthesized. The particle size of the hydrogel dispersions is 1–75 μm, its viscosity is less affected by temperature and salinity, and its residual resistance coefficient is higher than that of the polyacrylamide solution under similar apparent viscosity.

Block-copolymer-armed star polyampholyte with pH- and temperature-tunable supramolecular nanostructures for enhanced dye adsorption

The present investigation involves the synthesis of a series of block-copolymer-armed polyampholyte star polymers with sensitivity to changes in pH and temperature. The polymers are prepared using poly(2-hydroxyethyl methacrylate) core, while the arms are composed of a block copolymers consisting of acrylic acid and 2-(dimethylamino)ethyl methacrylate. The synthesis process involves a three-stage polymerization procedure utilizing reversible addition fragmentation chain transfer. The synthesized structures undergo characterization, and their self-assembly behavior is examined in relation to the adsorption of methylene blue, methyl orange, and the concurrent adsorption of both dyes. The development of spherical electrostatic complexes with varying diameters are seen as a consequence of pH variation. The present study investigates the impact of various parameters, including time, block location in the arms, pH, molecular weight, self-assembly effects, dye concentration, and temperature, on the process of adsorption. The study elucidates the adsorption phenomenon by examining its kinetics, thermodynamics, and adsorption isotherms. The findings of the study reveal that the greatest percentages of methylene blue adsorption are seen under alkaline pH conditions, whereas the most adsorption of methyl orange occurres under acidic pH conditions. The adsorption process by star-block polymers may be characterized as a spontaneous and endothermic mechanism, including heterojunction and multilayer adsorption. The polymers show promise for water purification applications due to their ability to simultaneously adsorb two dyes and their sensitivity to temperature and pH.

Embedding Thiols into Choline Phosphate Polymer Zwitterions.

The compositional scope of polymer zwitterions has grown significantly in recent years and now offers designer synthetic materials that are broadly applicable across numerous areas, including supracolloidal structures, electronic materials interfaces, and macromolecular therapeutics. Among recent developments in polymer zwitterion syntheses are those that allow insertion of reactive functionality directly into the zwitterionic moiety, yielding new monomer and polymer structures that hold potential for maximizing the impact of zwitterions on the macromolecular materials chemistry field. This manuscript describes the preparation of zwitterionic choline phosphate (CP) methacrylates containing either aromatic or aliphatic thiols embedded directly into the zwitterionic moiety. The polymerization of these functional CP methacrylates by reversible addition-fragmentation chain-transfer methodology yields polymeric zwitterionic thiols containing protected thiol functionality in the zwitterionic units. After polymerization, the protected thiols are liberated to yield thiol-rich polymer zwitterions which serve as precursors to subsequent reactions that produce polymer networks as well as polymer-protein bioconjugates.

Low Part-Per-Trillion, Humidity Resistant Detection of Nitric Oxide Using Microtoroid Optical Resonators.

The nitric oxide radical plays pivotal roles in physiological as well as atmospheric contexts. Although the detection of dissolved nitric oxide in vivo has been widely explored, highly sensitive (i.e., low part-per-trillion level), selective, and humidity-resistant detection of gaseous nitric oxide in air remains challenging. In the field, humidity can have dramatic effects on the accuracy and selectivity of gas sensors, confounding data, and leading to overestimation of gas concentration. Highly selective and humidity-resistant gaseous NO sensors based on laser-induced graphene were recently reported, displaying a limit of detection (LOD) of 8.3 ppb. Although highly sensitive (LOD = 590 ppq) single-wall carbon nanotube NO sensors have been reported, these sensors lack selectivity and humidity resistance. In this report, we disclose a highly sensitive (LOD = 2.34 ppt), selective, and humidity-resistant nitric oxide sensor based on a whispering-gallery mode microtoroid optical resonator. Excellent analyte selectivity was enabled via novel ferrocene-containing polymeric coatings synthesized via reversible addition-fragmentation chain-transfer polymerization. Utilizing a frequency locked optical whispering evanescent resonator system, the microtoroid's real-time resonance frequency shift response to nitric oxide was tracked with subfemtometer resolution. The lowest concentration experimentally detected was 6.4 ppt, which is the lowest reported to date. Additionally, the performance of the sensor remained consistent across different humidity environments. Lastly, the impact of the chemical composition and molecular weight of the novel ferrocene-containing polymeric coatings on sensing performance was evaluated. We anticipate that our results will have impact on a wide variety of fields where NO sensing is important such as medical diagnostics through exhaled breath, determination of planetary habitability, climate change, air quality monitoring, and treating cardiovascular and neurological disorders.

Degradable 3D Printed Objects with Tunable Mechanical Properties via Photoinduced Free Radical Promoted Cationic RAFT Polymerization

Degradable 3D Printed Objects with Tunable Mechanical Properties <i>via</i> Photoinduced Free Radical Promoted Cationic RAFT Polymerization