Polymer Nanocrystals Research Articles

Enhancement of Colorimetric pH-Sensitive Film Incorporating Amomum tsao-ko Essential Oil as Antibacterial for Mantis Shrimp Spoilage Tracking and Fresh-Keeping.

Anthocyanin-based smart packaging has been widely used for food freshness monitoring, but it cannot meet the requirements of smart films with antibacterial properties. This study aimed to enhance the antibacterial properties of intelligent films by incorporating Amomum tsao-ko essential oil (AEO) for mantis shrimp spoilage tracking and keeping the product fresh. A smart film was designed by introducing AEO and purple potato anthocyanin (PPA) to a polyvinyl alcohol/cellulose nanocrystal (PVA/CNC) polymer matrix. Our findings revealed that APP and AEO imparted the smart film with a favorable oxygen barrier, UV protection, mechanical properties, and antioxidant and pH/NH3-sensitive functions. Interestingly, the PVA/CNC-AEO-PPA film achieved 45.41% and 48.25% bactericidal efficacy against S. putrefaciens and V. parahaemolyticus, respectively. Furthermore, a visual observation confirmed that the target film (PVA/CNC-AEO-PPA) changed color significantly during mantis shrimp spoilage: rose red-light red-pink-light gray-dark gray. Meanwhile, the PVA/CNC-AEO-PPA film retarded the quality deterioration of the mantis shrimp effectively. The PVA/CNC-AEO-PPA film shows great application potential in mantis shrimp preservation and freshness monitoring; it is expected to become a rapid sensor for detecting seafood quality non-destructively and a multifunctional film for better preservation of product quality.

Chiral nematic nanocomposites with pitch gradient elaborated by filtration and ultraviolet curing of cellulose nanocrystal suspensions

An innovative method combining frontal filtration with ultraviolet (UV) curing has been implemented to design cellulosic nanocomposite films with controlled anisotropic textures from nanometric to micrometric length scales. Namely, an aqueous suspension containing poly (ethylene glycol) diacrylate polymer (PEGDA) as a photocurable polymer and cellulose nanocrystals (CNCs) at a 70/30 mass ratio was processed by frontal filtration, followed by in-situ UV-curing in a dedicated cell. This procedure allowed designing nanocomposite films with highly oriented and densely-packed CNCs, homogeneously distributed in a PEGDA matrix over a thickness of ca. 500 μm. The nanocomposite films were investigated with small-angle X-ray scattering (SAXS), by raster-scanning along their height with a 25 μm vertically-collimated X-ray beam. The CNCs exhibited a high degree of orientation, with their director aligned parallel to the membrane surface, combined with an increase in the degree of alignment as concentration increased towards the membrane surface. Scanning electron microscopy images of fractured films showed the presence of regularly spaced bands lying perpendicular to the applied transmembrane pressure, highlighting the presence of a chiral nematic (cholesteric) organization of the CNCs with a pitch gradient that increased from the membrane surface to the bulk.

Emergent Self-Assembly of Sustainable Plastics Based on Amino Acid Nanocrystals.

Development of biodegradable plastic materials is of primary importance in view of acute environmental and health problems associated with the accumulation of plastic waste. We fabricated a biodegradable composite material based on hydroxyethyl cellulose polymer and tyrosine nanocrystals, which demonstrates enhanced strength and ductility (typically mutually excluding properties), superior to most biodegradable plastics. This emergent behavior results from an assembly pattern that leads to a uniform nanoscale morphology and strong interactions between the components. Water-resistant biodegradable composites encapsulated with hydrophobic polycaprolactone as a protection layer were also fabricated. Self-assembly of robust sustainable plastics with emergent properties by using readily available building blocks provides a valuable toolbox for creating sustainable materials.

In vivo validation of a mechanically adaptive microfluidic intracortical device as a platform for sustained local drug delivery

Introduction: Intracortical microelectrodes (IME) are vital to properly functioning brain-computer interfacing (BCI). However, the recording electrodes have shown a steady decline in performance after implantation, mainly due to chronic inflammation. Compliant materials have been explored to decrease differential strain resulting in lower neural inflammation. We have previously developed a fabrication method for creating mechanically adaptive microfluidic probes made of a cellulose nanocrystal (CNC) polymer nanocomposite material that can become compliant after implantation. Here, we hypothesized that our device, would have a similar tissue response to the industry standard, allowing drug delivery therapeutics to improve neural inflammation in the future.Methods: RNA expression analysis was performed to determine the extent of neural inflammation and oxidative stress in response to the device compared to controls and to naïve shame tissue.Results: Results presented for both four- and eight-weeks post-implantations suggest that our device offers a promising platform technology that can be used to deliver therapeutic strategies to improve IME performance.

Transforming the Petroleum Industry through Catalytic Oxidation Reactions vis-à-vis Preceramic Polymer Catalyst Supports.

Preceramic polymers, for instance, are used in a variety of chemical processing industries and applications. In this contribution, we report on the catalytic oxidation reactions generated using preceramic polymer catalyst supports. Also, we report the full knowledge of the use of the remarkable catalytic oxidation, and the excellent structures of these preceramic polymer catalyst supports are revealed. This finding, on the other hand, focuses on the functionality and efficacy of future applications of catalytic oxidation of preceramic polymer nanocrystals for energy and environmental treatment. The aim is to design future implementations that can address potential environmental impacts associated with fuel production, particularly in downstream petroleum industry processes. As a result, these materials are being considered as viable candidates for environmentally friendly applications such as refined fuel production and related environmental treatment.

Enhanced Hygrothermal Stability of In-Situ-Grown MAPbBr3 Nanocrystals in Polymer with Suppressed Desorption of Ligands.

Currently, the intrinsic instability of organic-inorganic hybrid perovskite nanocrystals (PNCs) at high temperature and high humidity still stands as a big barrier to hinder their potential applications in optoelectronic devices. Herein, we report the controllable in-situ-grown PNCs in polyvinylidene fluoride (PVDF) polymer with profoundly enhanced hygrothermal stability. It is found that the introduced tetradecylphosphonic acid (TDPA) ligand enables significantly improved binding to the surface of PNCs via a strong covalently coordinated P-O-Pb bond, as evidenced by density functional theory calculations and X-ray photoelectron spectroscopy analyses. Accordingly, such enhanced binding could not only make efficient passivation of the surface defects of PNCs but also enable the remarkably suppressed desorption of the ligand from the PNCs under high-temperature environments. Consequently, the photoluminescence quantum yield (PL QY) of the as-fabricated MAPbBr3-PNCs@PVDF film exhibits almost no decay after exposure to air at 333 K over 1800 h. Once the temperatures are increased from 293 to 353 K, their PL intensity can be kept as 88.6% of the initial value, much higher than that without the TDPA ligand (i.e., 42.4%). Moreover, their PL QY can be maintained above 50% over 1560 h (65 days) under harsh working conditions of 333 K and 90% humidity. As a proof of concept, the as-assembled white light-emitting diodes display a large color gamut of 125% National Television System Committee standard, suggesting their promising applications in backlight devices.

Solution-processed ferroelectric polymer nanocrystals

Since the first demonstrations of ferro- and piezoelectricity in solution-processed ferroelectric polymer thin films research activities have been stimulated in both academia and industry. Several applications have been reported using ferroelectric polymer thin films as bistable polarization switches in memory devices or as transducers in (micro-)electromechanical devices. In light of the continuing miniaturization of such devices, nanoscaled structures of ferroelectric polymers such as nanomesas are attracting increasing interest. However, nanopatterning ferroelectrics, to develop stable and reliable ferroelectric nanomesas remains challenging. In this work, we demonstrate the fabrication of solution-processed ferroelectric polymer nanocrystals, i.e. ferroelectric nanomesas, and verify their ferroelectric activity. By using the ferroelectric copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)), we are able to isolate crystalline domains. Morphology, molecular conformation, (nano-)mechanical and electromechanical properties of the nanocrystals are measured, yielding comparable results to those observed in uniform, continuous thin films. Therefore, synthesizing self-assembled ferroelectric polymer nanocrystals from polymer solution by spin-casting represents a promising approach for the realization of ferroelectric nanomesas.

Dual-Functional Super-Assembled Mesoporous Carbon-Titania/AAO Hetero-Channels for Bidirectionally Photo-Regulated Ion Transport.

Photo-regulated nanofluidic devices have attracted great attention in recent years due to their adjustable ion transport in real time. However, most of the photo-responsive nanofluidic devices can only adjust the ionic current unidirectionally, and cannot simultaneously increase or decrease the current signal intelligently by one device. Herein, a mesoporous carbon-titania/ anodized aluminum hetero-channels (MCT/AAO) is constructed by super-assembly strategy, which exhibits dual-function of cation selectivity and photo response. The polymer and TiO2 nanocrystals jointly build the MCT framework. Polymer framework with abundant negatively charged sites endows MCT/AAO with excellent cation selectivity, and TiO2 nanocrystals are responsible for the photo-regulated ion transport. High photo current densities of 1.8mAm-2 (increase) and 1.2mAm-2 (decrease) are realized by MCT/AAO benefiting from the ordered hetero-channels. Significantly, MCT/AAO can also achieve the bidirectionally adjustable osmotic energy by alternating the configurations of concentration gradient. Theoretical and experimental results reveal that the superior photo-generated potential is responsible for the bidirectionally adjustable ion transport. Consequently, MCT/AAO performs the function of harvesting ionic energy from the equilibrium electrolyte solution, which greatly expands its practical application field. This work provides a new strategy in constructing dual-functional hetero-channels toward bidirectionally photo-regulated ionic transport and energy harvesting.

Chiral nematic liquid crystal organization of natural polymer nanocrystals

ABSTRACT One-dimensional nanocrystals with high-aspect ratio from natural polymers such as cellulose nanocrystals are attractive due to their anisotropic dimensions, versatile surface chemistry and ability to form lyotropic liquid crystalline (LC) phase in aqueous media. Most importantly, those anisotropic natural materials preserve their LC ordering in solid films under slow drying at ambient conditions. The resulting organised films with ‘frozen’ chiral nematic helicoidal morphology show unique optical properties such as selective light reflection, high optical birefringence, selective circular polarisation, along with enhanced mechanical performance, e.g. high ultimate strength, toughness and stretchability. Additionally, those films are lightweight, and potentially sustainable and biodegradable. Here we briefly overview recent work from our group on the chiral nematic organisation in LC suspensions and in thin films of cellulose nanocrystals and cellulose nanofibers obtained under diverse interparticle interactions, confined drying conditions, and external magnetic field.

Morphology and orientation change of layer-by-layer deposited one- and two-dimensional coordination polymer nanocrystals containing rhodium paddle-wheel units

“Layer-by-layer” deposits of coordination polymers show a rich morphology spectrum and display unusual structural transformations as a function of the deposition cycle number.

Metal halide perovskite nanocrystal with fluorescence enhancement in wet and acidic environment

Metal halide perovskite nanocrystals have excellent prospects in solid-state lighting, flexible display, sensing, and other optoelectronic applications due to their superb photoelectric properties (high quantum efficiency and fast carrier diffusion speed). However, they are susceptible to environmental factors such as ultraviolet radiation and polar solvents. Especially in a water environment, poor stability seriously restricts the application of perovskite optical devices. In this paper, a kind of porous polymer (ethylene-vinyl acetate copolymer, EVA) and perovskite nanocrystals were mixed to form perovskite nanocrystals-EVA composites. The obtained composites were aged in water for 21 days, and the fluorescence enhancement was 170 times. Even in a strongly acidic environment, the fluorescence enhancement was 91 times. The information encryption mode of the composite material can effectively encrypt information in a wet environment due to the change of light wavelength, making a white light-emitting diode (w-LED). This metal halide perovskite nanocrystals-EVA composite will unleash a wide variety of solid-state lighting and flexible display possibilities that are limited by the use of existing methods in humid and strongly acidic environments.

In Situ Constructed Nanocrystal Structure and Its Contribution in Shape Memory Performance of Pure Polylactide

Crystal size plays an essential role in the performance of polymers. Generally, direct processing of common spherulites into nanocrystals (NCs) is hardly applied since polymer spherulites always shape into fibrous crystals and are hard to flow again. In this study, polylactide (PLA) lamellae of spherulites are first diluted by amorphous PLA. Then, PLA NCs are constructed in situ by intense stress, which is transferred by the amorphous polylactide in a high elastic state. The NCs and their network formed in bulk endow pure polylactide with excellent shape memory features. A strong shape recovery initiation force (around 4–5 MPa) and an enhancement of 41.6% in the shape recovery ratio with 30 wt % NCs in PLA are achieved compared with traditional PLA. This study presents a new common methodology for the industrial production of polymer NCs.

Wavelength-Tunable and Water-Stable Cesium-Lead-Based All-Bromide Nanocrystal-Polymer Composite Films Using Ultraviolet-Curable Prepolymer as an Anti-Solvent.

All-inorganic metal halide perovskite nanocrystals (IPeNCs) have become one of the most promising luminescent materials for next-generation display and lighting technology owing to their excellent color expression ability. However, research on IPeNCs with stable blue emission is limited. In this paper, we report stable blue emissive all-bromide IPeNCs obtained through a modified ligand-assisted reprecipitation method using an ultraviolet (UV)-curable prepolymer as the anti-solvent at a low temperature. We found that the blue emission originates from quantum-confined CsPbBr3 nanoparticles formed together with the colorless wide-bandgap Cs4PbBr6 nanocrystals. When the temperature of the prepolymer was increased from 0 to 50 °C, CsPbBr3 nanoparticles became larger and more crystalline, thereby altering their emission color from blue to green. The synthesized all-bromide blue-emitting IPeNC solution remained stable for over 1 h. It also remained stable when it was mixed with the green-emitting IPeNC solution. By simply exposing the as-synthesized IPeNC–prepolymer solutions to UV light, we formed water-stable composite films that emitted red, green, blue, and white colors. We believe that this synthetic method can be used to develop color-emitting composite materials that are highly suitable for application as the color conversion films of full-color liquid crystal display backlight systems and lighting applications.

Switchable Anion Exchange in Polymer-Encapsulated APbX3 Nanocrystals Delivers Stable All-Perovskite White Emitters.

We report a one-step synthesis of halide perovskite nanocrystals embedded in amphiphilic polymer (poly(acrylic acid)-block-poly(styrene), PAA-b-PS) micelles, based on injecting a dimethylformamide solution of PAA-b-PS, PbBr2, ABr (A = Cs, formamidinium, or both) and “additive” molecules in toluene. These bifunctional or trifunctional short chain organic molecules improve the nanocrystal–polymer compatibility, increasing the nanocrystal stability against polar solvents and high flux irradiation (the nanocrystals retain almost 80% of their photoluminescence after 1 h of 3.2 w/cm2 irradiation). If the nanocrystals are suspended in toluene, the coil state of the polymer allows the nanocrystals to undergo halide exchange, enabling emission color tunability. If the nanocrystals are suspended in methanol, or dried as powders, the polymer is in the globule state, and they are inert to halide exchange. By mixing three primary colors we could prepare stable, multicolor emissive samples (for example, white emitting powders) and a UV-to-white color converting layer for light-emitting diodes entirely made of perovskite nanocrystals.

Highly Stable Waterborne Luminescent Inks Based on MAPbBr3@PbBr(OH) Nanocrystals for LEDs and Anticounterfeit Applications.

Waterborne polymers are advantageous in terms of cost, convenience, sustainability, and environmental friendliness. As lead halide perovskite (LHP) nanocrystals suffer from fast degradation in the presence of water, it is challenging to encapsulate LHP nanocrystals in waterborne polymers. In this work, luminescent MAPbBr3@PbBr(OH) nanocrystals were synthesized via the aqueous grinding process in the presence of 2-methyl-imidazole (2-MIM) and oleylamime (OAm). 2-MIM triggers the formation of the PbBr(OH) matrix, and OAm acts as a size-control ligand to control the size of MAPbBr3@PbBrOH particles in the nanoscale range. Highly stable waterborne luminescent inks were successfully prepared by blending MAPbBr3@PbBr(OH) nanocrystals with waterborne polymers, including poly(vinylpyrrolidone), poly(vinyl acetate), and acrylate resins. Owning to the dual protection of the polymer matrix and PbBr(OH) to LHP quantum dots (QDs), the luminescent films exhibit excellent stability to the environment under thermal and light irradiation. The ink can be used as a phosphor to fabricate down-converting green and white light-emitting diodes (LEDs). Waterborne anticounterfeiting inks suitable for screen printing were prepared via formula tuning for the anticounterfeit purpose. The anticounterfeiting luminescent patterns can be screen printed on paper, cloth, and poly(ethylene terephthalate) (PET), with encryption and decryption of information being accurately and conveniently realized by switching UV irradiation.

Hybrid white light emitting devices (HWLEDs) from organic polymer and PbS nanocrystals by multiple excitons

Abstract Hybrid white light-emitting devices (HWLEDs) were fabricated using FTO/PEDOT: PSS/PbS/Alq3/Ni system and synthesized by phase separation process. In the present study, the multiple excitons generation in lead sulfide (PbS) NCs, which is characteristic of PbS NCs, was used to induce an effective and regulated energy transfer to an HWLED. The HWLED consisted of three layers successively deposited on FTO glass substrate; the first layer consisted of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) blended with polymethyl methacrylate (PMMA) organic polymer in the 1:1 ratio, while the second layer consisted of PbS NCs. Finally, above the layer of the PbS NCs, Tris (8-hydroxyquinoline) aluminum (Alq3) layer was deposited. The white light was generated with quite a good efficiency due to the confinement effect that makes the energy gap greater. The characteristics of the current-voltage (I-V) indicate acceptable conditions for the generation of white light by multiple excitons. It was found that the emission levels able to produce white luminescence, classified based on the coordinate system of chromaticity (CIE 1931), are x = 0.31, y = 0.33 while the correlated color temperature (CCT) is about 6250 K. The HWLEDs made from PbS NCs with hole injection from the organic polymer (PEDOT: PSS with PMMA), and electron injection from organic molecules (Alq3) are capable of white light generation.

Mechanical and Optical Properties of Stretchable Silicon Nanocrystal/Polydimethylsiloxane Nanocomposites

Nanoparticle‐infused polymer composites have long been an area of interest due to the typically stabilizing effects they have on the mechanical behavior of the composites, as well as added functionalities such as reduced surface resistance. Newer applications of these nanocomposites include dispersing optoelectronically functional nanoparticles in polymer matrices, for example, including luminescent nanocrystals in rigid slabs for luminescent solar concentrating photovoltaics and electrochromic panels. Dispersion of luminescent nanocrystals in stretchable polymers adds novel possibilities for applications, such as wearable health monitoring systems, flexible communications devices, and more. To leverage the exciting combined properties that these nanocomposites promise, there is a pressing need to evaluate and understand the interconnections between the optical effects, mechanical behavior, and the properties of the constituents. Herein, the optical and mechanical behavior of brightly emissive silicon nanocrystal/polydimethylsiloxane (PDMS) nanocomposites are investigated as a function of nanocrystal concentration and nanocrystal surface functionality. Mechanically, incorporating the nanocrystals at higher concentration leads to a dramatic reduction in the mechanical properties of the nanocomposite. The results suggest that the nanocrystal inclusions interfere with polymer cross‐linking, changing the mechanical behavior of the host PDMS as compared to the control.

Chemically Controllable Porous Polymer–Nanocrystal Composites with Hierarchical Arrangement Show Substrate Transport Selectivity

Functional organic–inorganic hybrid materials with tunable properties are useful across many application areas, ranging from gas storage to electronics, flame retardants, separations, and catalysis. Combining polymers, with a suite of functional groups and conformational flexibility, and inorganic nanoparticles, with tunable surface chemistry and composition, yields hybrids with novel functional properties. Specifically, in catalysis, control of the electronic environment at a metal interface is paramount in determining the catalytic properties. In this contribution, we describe a modular process to prepare porous polymer–nanocrystal (NC) composites in a hierarchical, multilayered synthesis, in which multiple parameters can be accurately tuned: polymer functional groups and the corresponding pore structure, the polymer layer thickness, and the NC size, shape, and composition. This process provides for a variety of controlled materials with high surface area, tunable chemistry, and thermal and chemical stabilities. Furthermore, we demonstrate their utility for shape- and size-selective catalytic conversions both in oxidation and hydrogenation reactions, where they show increased selectivity by orders of magnitude compared to conventional polymer-supported metal catalysts. In light of the high degree of control in the composite structure, this method allows for the design and realization of catalysts for several reactions and reaction environments and for nanomaterials with other applications.

X-ray ptychographic mode of self-assembled CdSe/CdS octapod-shaped nanocrystals in thick polymers

This work describes the application of X-ray ptychography for the inspection of complex assemblies of highly anisotropic nanocrystals embedded in a thick polymer matrix. More specifically, this case deals with CdSe/CdS octapods, with pod length L = 39 ± 2 nm and pod diameter D = 12 ± 2 nm, dispersed in free-standing thick films (24 ± 4 µm) of polymethyl methacrylate and polystyrene, with different molecular weights. Ptychography is the only imaging method available to date that can be used to study architectures made by these types of nanocrystals in thick polymeric films, as any other alternative direct method, such as scanning/transmission electron microscopy, can be definitively ruled out as a result of the large thickness of the free-standing films. The electron density maps of the investigated samples are reconstructed by combining iterative difference map algorithms and a maximum likelihood optimization algorithm. In addition, post image processing techniques are applied to both reduce noise and provide a better visualization of the material morphological details. Through this process, at a final resolution of 27 nm, the reconstructed maps allow us to visualize the intricate network of octapods inside the polymeric matrices.

MnO Nanoparticles Embedded in Functional Polymers as T1 Contrast Agents for Magnetic Resonance Imaging

The design and development of contrast agents (CAs) for magnetic resonance imaging (MRI) in clinical analysis is expected to improve the image spatial resolution and to increase the detection sensitivity, especially regarding neurological disorders and cancer disease. In particular, advanced CAs for T1-weighted images are investigated to achieve the sensitive detection of early-stage primary tumors or brain metastases. In this study, we present a strategy toward diagnostic T1 CAs for MRI, based on polymer-modified MnO nanoparticles (NPs). Two different nanosystems were synthesized, consisting of (1) colloidal MnO nanocrystals wrapped by a multidentate amphiphilic polymer and (2) MnO nanocrystals embedded within poly(lactic-co-glycolic acid) (PLGA) NPs. These nanosystems were compared in terms of their MRI contrast power and biological safety. The latter system combines the excellent biocompatibility of PLGA with the unique magnetic properties of MnO NPs and allows sustained contrast enhancement over time. Longitudinal relaxivities of both MnO composite nanomaterials proved to be higher than those of commercial Gd-based CAs and Teslascan, both in phosphate-buffered saline and in plasma, also exhibiting low cytotoxicity. The high relaxation rates achieved with these contrast enhancers are promising toward future application in in vivo imaging.