Composition Of Nanocrystals Research Articles

Formamidinium Lead Halide Perovskite Nanocomposite Scintillators.

While there is great demand for effective, affordable radiation detectors in various applications, many commonly used scintillators have major drawbacks. Conventional inorganic scintillators have a fixed emission wavelength and require expensive, high-temperature synthesis; plastic scintillators, while fast, inexpensive, and robust, have low atomic numbers, limiting their X-ray stopping power. Formamidinium lead halide perovskite nanocrystals show promise as scintillators due to their high X-ray attenuation coefficient and bright luminescence. Here, we used a room-temperature, solution-growth method to produce mixed-halide FAPbX (X = Cl, Br) nanocrystals with emission wavelengths that can be varied between 403 and 531 nm via adjustments to the halide ratio. The substitution of bromine for increasing amounts of chlorine resulted in violet emission with faster lifetimes, while larger proportions of bromine resulted in green emission with increased luminescence intensity. By loading FAPbBr nanocrystals into a PVT-based plastic scintillator matrix, we produced 1 mm-thick nanocomposite scintillators, which have brighter luminescence than the PVT-based plastic scintillator alone. While nanocomposites such as these are often opaque due to optical scattering from aggregates of the nanoparticles, we used a surface modification technique to improve transmission through the composites. A composite of FAPbBr nanocrystals encapsulated in inert PMMA produced even stronger luminescence, with intensity 3.8× greater than a comparative FAPbBr/plastic scintillator composite. However, the luminescence decay time of the FAPbBr/PMMA composite was more than 3× slower than that of the FAPbBr/plastic scintillator composite. We also demonstrate the potential of these lead halide perovskite nanocomposite scintillators for low-cost X-ray imaging applications.

Photomechanical Structures Based on Porous Alumina Templates Filled with 9-Methylanthracene Nanowires

9-Methylanthracene (9MA) undergoes a concerted [4 + 4] photodimerization in its crystal form that can be harnessed in order to generate photomechanical motions such as bending, twisting, and expansion. As described in this paper, 9MA nanowires were grown in anodic aluminum oxide (AAO) templates with the goal of using the crystal expansion to generate a net increase in the height of the composite disk. The growth conditions were optimized in order to raise the filling amount from 28% to 77% of the available volume in the porous AAO. A new experimental method for detecting motion, based on the analysis of data from a dynamically misaligned Michelson interferometer, was developed. Template bending was observed, showing that the photodimerization of the confined nanowires generated mechanical work, but no conclusive evidence for surface disruption or vertical translation was observed. Optical measurements, as well as atomic force and scanning electron microscopy, showed that incomplete filling, crystal orientation, and debris from template polishing likely prevented the observation of vertical actuation in these nanocrystal composites. This work highlights some of the practical challenges that are involved in creating photomechanical actuators using the organic–inorganic composite approach, with the two most significant being (1) the uniform filling of the porous template with the organic active material and (2) the removal of excess organic material from the template’s surface.

Fully biodegradable Poly(butylene succinate-co-1,2-decylene succinate)/Cellulose nanocrystals composites with significantly enhanced crystallization and mechanical property*

Poly (butylene succinate-co-1,2-decylene succinate) (PBDS) is a promising biodegradable polyester with n-octyl being the side group (Polymer 2021, 213, 123197). The toughness of PBDS is significantly higher than that of linear poly (butylene succinate) (PBS), while the tensile strength and crystallization rate of PBDS are remarkably lower than those of PBS. In this research, fully biodegradable PBDS/cellulose nanocrystals (CNC) composites were prepared at low CNC loadings with the aim of improving the crystallization and mechanical properties. The surface morphology study suggested CNC achieved an even distribution in PBDS. As an efficient heterogeneous nucleating agent, CNC obviously enhanced the nonisothermal melt crystallization behavior and isothermal melt crystallization kinetics of PBDS, as evidenced by the upward shift of melt crystallization temperature and shorter crystallization half-time. Both the nucleation activity and nucleation efficiency of CNC were quantitively evaluated, which were 0.40 and 44.9%, respectively, at a CNC loading of 2 wt%. CNC did not change the crystallization mechanism and crystal structure of PBDS. The mechanical properties study indicated that the tensile mechanical properties (Young's modulus and tensile strength from the tensile test) and storage modulus (from dynamic mechanical analysis) of PBDS were obviously enhanced by CNC, indicating the reinforcement effect.

Effect of silica encapsulation on the stability and photoluminescence emission of FAPbI3 nanocrystals for white-light-emitting perovskite diodes

The α-FAPbI 3 perovskite nanocrystals exhibit interesting optical properties, which make them attractive for versatile optoelectronic applications; however, the spontaneous phase transformation to the non-perovskite phase (δ-FAPbI 3 ) in humid conditions requires a new strategy to improve the phase stability of the material. We employed 3-Aminopropyl triethoxysilane (APTES)-assisted reprecipitation and sol-gel methods at ambient temperature to prepare stable α-FAPbI 3 nanocrystals embedded in a silica matrix. Transmission electron microscopy (TEM) and X-ray diffraction analysis determined that ultrafine perovskite nanocrystals (11.5 ± 3 nm) were uniformly distributed in a silica matrix. Investigations of the optical properties of the synthesized materials revealed that about 94% of the photoluminescence (PL) emission of silica-encapsulated FAPbI 3 nanocrystals was preserved under humid conditions (60%) after at least a month, while the PL emission of untreated FAPbI 3 was significantly decayed after few days. The thermal analysis also determined that the thermal stability of FAPbI 3 nanocrystals was improved by silica encapsulation. The red-emitting silica-encapsulated FAPbI 3 nanocrystals with a wavelength of 720 nm were used to fabricate white light-emitting diodes (LEDs) in a vertical structure consisting of a blue-chip, PMMA/CsPbBr 3 QDs, and PMMA/FAPbI 3 -SiO 2 QDs. Stable perovskite-based white LEDs with a color gamut of 144% NTSC were fabricated, which was better than many phosphor-based and perovskite-based LEDs. The synthesized composite perovskite nanocrystals could be used for next-generation optoelectronic devices. • Synthesis of silica-encapsulated FAPbI 3 quantum dots at ambient temperature by a combined LARP and sol-gel process. • Minor PL intensity loss in the humidified atmosphere after few months. • WLEDs with a high color gamut of 144% NTSC. • A pure red LED with coordination (0.729, 0.270).

Composites of cellulose nanocrystals in combination with either cellulose nanofibril or carboxymethylcellulose as functional packaging films

Cellulose nanocrystals (CNC) were mixed with either cellulose nanofibril (CNF) or carboxymethylcellulose (CMC) in variable proportions (0/100, 20/80, 40/60, 50/50, 60/40, 80/20 and 100/0) to obtain cast films with acceptable barrier and mechanical properties as replacements for food packaging plastics. Both CNF and CMC improved tensile strength, elongation, UV opacity, air resistance, hydrophobicity (WCA-water contact angle), water vapor transmission rate (WVTR) and oxygen impermeability in pure CNC. WVTR and oxygen permeability were strongly dependent on relative humidity (RH). Interestingly, the greatest effect on WVTR was observed at RH = 90% in films containing CMC in proportions above 60%. CMC- and CNF-containing films had oxygen impermeability up to an RH level of 80% and 60%, respectively. The previous effects were confirmed by food packaging simulation tests, where CMC-containing films proved the best performers. The composite films studied were biodegradable—which constitutes a major environmental related advantage—to an extent proportional to their content in CMC or CNF.

Photoluminescence Sensing of Chloride Ions in Sea Sand Using Alcohol-Dispersed CsPbBr3@SiO2 Perovskite Nanocrystal Composites

In this study, CsPbBr3@SiO2 perovskite nanocrystal composites (CsPbBr3@SiO2 PNCCs) were synthesized by a benzyl bromide nucleophilic substitution strategy. Homogeneous halide exchange between CsPbBr3@SiO2 PNCCs and Cl− solution (aqueous phase) was applied to the determination of Cl− in sea sand samples. Fast halide exchange with Cl− in the aqueous phase without any magnetic stirring or pH regulation resulted in the blue shift of the photoluminescence (PL) wavelength and vivid PL color changes from green to blue. The results show that the PL sensing of Cl− in aqueous samples could be implemented by using the halide exchange of CsPbBr3@SiO2 PNCCs. A linear relationship between the PL wavelength shift and the Cl− concentration in the range of 0 to 3.0% was found, which was applied to the determination of Cl− concentration in sea sand samples. This method greatly simplifies the detection process and provides a new idea for further broadening PL sensing using the CsPbBr3 PNC halide.

Composites of Silver Nanoclusters and Cellulose Nanocrystals with Tunable Emission as Multicolor Inks

Composites of Silver Nanoclusters and Cellulose Nanocrystals with Tunable Emission as Multicolor Inks

Ultrastable highly-emissive amphiphilic perovskite nanocrystal composites via the synergy of polymer-grafted silica nanoreactor and surface ligand engineering for white light-emitting diode

Instability of perovskite nanocrystals driven by their ionic crystal characteristic poses a grand challenge for long-term practical applications in optoelectronic materials and devices. Herein, we report the crafting of amphiphilic perovskite nanocrystal composites (APNCCs) with a set of markedly improved stabilities via capitalizing on polymer-grafted silica nanosheets as nanoreactors in conjunction with surface ligand engineering. First, SiO2 nanosheets grafted with poly(acrylic acid)-block-polystyrene (denoted SiO2 @PAA-b-PS) are rationally designed and exploited as nanoreactors to form SiO2 @CsPbBr3 @PS. Subsequent passivation with small-molecule ligands (L) yields highly emissive SiO2 @CsPbBr3 @ (PS/L) APNCCs with an array of outstanding stabilities against UV, heat, water, long-term storage, and various polar organic solvents. Remarkably, our strategy integrating polymer-grafted SiO2 nanosheet nanoreactor with surface ligand engineering is general and viable. A diversity of stable APNCCs can be readily created. Finally, white light-emitting diode (WLED) with wide color gamut and excellent stability composed of green-emitting SiO2 @CsPbBr3 @ (PS/L) APNCCs is demonstrated. This work highlights the robustness of the synergy of judiciously-designed nanoreactor and surface ligand engineering to produce highly emissive, ultrastable perovskite nanocrystals shielded with soft and hard materials (i.e., possessing a Janus surface chemistry).

Design and fabrication of recyclable and reshape vitrified elastomer reinforced with renewable cellulose nanocrystal

Developing the recyclable elastomeric vitrimer with dynamic covalent bonds is a very promising strategy to alleviate the burden of traditional vulcanized rubber materials on the environment. In this work, we proposed to introduce epoxidized soybean oil (ESO) as a cross-linking agent into carboxyl nitrile butadiene rubber (XNBR)/TEMPO-oxidized cellulose nanocrystals (TO-CNC) composites, and successfully prepared ESO-cured XNBR/TO-CNC elastomeric vitrimer with dynamic β-hydroxyl ester bonds, which are formed between the epoxy group of ESO and the carboxyl group of XNBR or TO-CNC. The TEMPO oxidation of CNC is validated by a series of characterizations such as FTIR, conductometric titration, and element analysis. The formation of the β-hydroxyl esters is as well evidenced by the FTIR analysis and the curing curves. Interestingly, the TO-CNC exhibits good dispersion in the composite, and a remarkable mechanical reinforcement is observed for ESO-cured XNBR/TO-CNC elastomer, for instance, the tensile strength of the composite with 15 phr TO-CNC was 2.4 times greater than that of the unfilled sample. Moreover, this composite as well shows good reshaping capability and reprocessability. Generally, this work offers a novel approach to preparing green cross-linked elastomer/bio-based CNC composites that can potentially overcome the bottleneck of the non-recycling of traditional vulcanized rubber.

Synthesis of super-hydrophobic and self-cleaning magnetic graphene aerogel with excellent microwave absorption properties

The well-established structure and ultra-fine nanoparticles are vital for high-performance microwave absorption materials. Herein, three-dimensional hydrophobic graphene aerogels decorated with ultra-fine Fe3O4 nanocrystals composites (HGAFX, X stands for pyrolysis temperature) were successfully constructed via chemically self-assembly and in situ pyrolysis. Remarkably, the hybrids with only 5% filling contents exhibited excellent microwave absorption performance (MAP) in terms of both minimum reflection loss (RLmin) and effective absorption bandwidth (EAB), outperforming the most reported microwave absorbers. Moreover, the magnetic graphene aerogels composites possess strong hydrophobicity, endowing them attractive functions of self-cleaning, waterproof, anti-icing, and corrosion resistance. Importantly, experimental results and theoretical calculations indicate that superior MAP can be carried out by reasonably regulating the electromagnetic parameters. Considering the excellent absorption capacities, our strategy opened a novel way for anchoring ultra-small nanoparticles on graphene sheets as highly effective synergistic microwave absorbers at low filling contents.

Tuning Exchange Coupling in a New Family of Nanocrystal-Based Granular Multiferroics Using an Applied Electric Field.

In this work, we demonstrate an experimental realization of a granular multiferroic composite, where the magnetic state of a nanocrystal array is modified by tuning the interparticle exchange coupling using an applied electric field. Previous theoretical models of a granular multiferroic composite predicted a unique magnetoelectric coupling mechanism, in which the magnetic spins of the ensemble are governed by interparticle exchange. The extent of these exchange interactions can be controlled by varying the local dielectric environment between grains. We specifically utilize the strong dielectric dependence of ferroelectric materials to modify the interparticle coupling of closely spaced magnetic nanoparticles using either a change in temperature or an electric field. This coupling modifies the ensemble magnetic coercivity and thus the superparamagnetic-to-ferromagnetic phase transition temperature. Through the use of two different ferroelectrics, our results suggest that this magnetoelectric coupling mechanism could be generalized as a new class of multiferroic material, applicable to a broad range of ferroelectric/magnetic nanocrystal composites.

Antibiotics adsorption from contaminated water by composites of ZSM-5 zeolite nanocrystals coated carbon

The presence of antibiotic residues such as ciprofloxacin (CIPR) in an aqueous environment is dangerous when their concentrations exceed the allowable. Therefore, eliminating these residues from the wastewater becomes an essential issue to prevent their harm. In this work, the potential of efficient adsorption of ciprofloxacin antibiotics was studied using eco-friendly ZSM-5 nanocrystals‑carbon composite (NZC). An inexpensive effective natural binder made of the sucrose-citric acid mixture was used for preparing NZC. The characterization methods revealed the successful preparation of NZC with a favorable surface area of 103.739 m2/g, and unique morphology and functional groups. Investigating the ability of NZC for adsorbing CIPR antibiotics conducted at different conditions showed that 0.3 g of NZC achieved outstanding adsorption for 150 ppm CIPR antibiotic from 100 mL solutions at mixing speed of 200 rpm, solution pH of 4–6, and solution temperature of 25–30 °C. Estimating the values of ∆H°, ∆S°, and ∆G° confirmed that the adsorption process of CIPR antibiotics by NZC was feasible, exothermic and spontaneous. The Freundlich and pseudo-second-order models well fitted the adsorption process's experimental data. The results of both the kinetic and isotherm studies showed that the adsorption process of CIPR antibiotics by NZC is simultaneously composed of physical and chemical adsorption on the heterogeneous adsorption sites in multilayers. Also, the intra-particle diffusion was not the controlling step and the external surface adsorption influenced the adsorption of CIPR. From the abovementioned results, NZC is recommended as a highly efficient adsorbent for the removal of CIPR-loaded effluents.

Cellulose Nanocrystals from Postconsumer Cotton and Blended Fabrics: A Study on Their Properties, Chemical Composition, and Process Efficiency

From manufacturing to disposal, the textile industry faces multiple challenges to achieve sustainability and reduce its environmental impact. This work investigates the properties and composition of cellulose nanocrystals (CNCs) extracted from clothing waste made of cotton fibers. We isolated CNCs from cotton, polyester/cotton, and acrylic/cotton waste fabrics through acid hydrolysis with sulfuric acid. A yield of 51–62 wt % (cotton basis) was obtained, and nearly all the polyester and acrylic fibers contained in the initial fabrics were recovered in a convenient shape that could allow easier recycling. CNCs extracted from the selected fabrics showed high purity, similar structural, physical, and chemical characteristics, and their properties were comparable to those extracted from virgin sources, although their surface chemistry and elemental composition slightly differed. The chemical components in the waste fabrics and the extracted CNCs were evaluated through a nontarget chromatographic-mass spectrometric screening strategy. Both the recycled textiles and the CNCs contained hundreds of compounds common in postconsumer textiles, including some with health and environmental concerns. However, our initial findings show that their concentrations in the CNCs are negligible. Our results provide insights into the challenges associated with the use of cotton waste textiles for the extraction of cellulose nanoparticles, and into the potential applications of the extracted nanomaterials.

Carbon/Cr2O3 nanocrystal Composites as an Anode with Improved Lithium Storage Performance

Carbon/Cr2O3 nanocrystal Composites as an Anode with Improved Lithium Storage Performance

General and facile synthesis of robust composite nanocrystals with natural peach gum polysaccharide

Composite nanocrystal (CN) composed of inorganic nanocrystal and polymer has attracted great interest because of its attractive synergetic properties and wide applications. Herein, we present a simple and general method for the synthesis of various CNs (e.g., noble metal, magnetic, semiconductor and silver halide) based on the use of natural peach gum polysaccharide (PGP) as a capping agent. PGP with highly branched topological structure and abundant functional groups can not only induce the formation of CNs, but also endow the CNs with good aqueous dispersibility and stability. Thanks to the capping of PGP, the obtained CNs simultaneously possess small and relatively uniform size, numerous tailorable functional groups and low cytotoxicity. In addition, it is also confirmed that some CNs (e.g., PGP-Au and PGP-AgBr) can be utilized as a catalyst with high catalytic activity due to their accessible surface for substrate molecules. Considering the easy synthesis process and robust performance of CNs, this study opens up a new opportunity for scalable synthesis of applicable CNs.

Recyclable, self-healable and reshape vitrified poly-dimethylsiloxane composite filled with renewable cellulose nanocrystal

Traditional thermoset polymeric materials pose an enormous burden on the environment due to permanent covalent cross-links that make them difficult to reprocess or recycle. Herein, we describe the facile synthesis of recyclable, healable and reprocessable poly-dimethylsiloxane (PDMS)/cellulose nanocrystals (CNC) composites via engineering dynamic covalent bond (DCB) vinylogous urethane between the polymer-polymer and polymer-CNC. We successfully prepared the amine-modified CNC, evidenced by the analysis of FTIR, XPS and Element analysis, and its surface morphology as well as its size compared to the pristine one is not altered via XRD and TEM analysis. The DCBs are constructed not only between polymer chains, but also on the interface between polymer and CNC. Interestingly, the macromolecular cross-linker synthesized by RAFT polymerization significantly improves the mechanical properties of PDMS-based CNC vitrimer, without affecting its recycling and reprocessing properties. Remarkably, DCB vinylogous urethane endows this vitrimer good self-healing, reprocessing and recycling and this DCB can be effectively reshaped by the catalyst-free transamination of the vinylogous urethane through hot pressing or welding. It is emphasized that this macromolecular cross-linker containing β-keto acids obtained by RAFT polymerization can significantly broaden the application range for DCB vinylogous urethane. In general, this work could provide a facile approach to design and fabricate high performance renewable CNC based composites with excellent self-healing, reprocessing and recycling capabilities.

In situ preparation of nanohydroxyapatite/alginate composites as additives to PVA electrospun fibers as new bone graft materials

Aiming at new fibers containing hydroxyapatite (HAp) nanocrystal composites for bone graft applications, we successfully induced in situ growth of the ceramic phase in alginate gel (HAL) added them as dried materials at 0.1, 0.25 and 0.5% (w/w) to PVA matrices to prepare electrospun fibers. X-ray diffraction pattern and transmission electron microscopy showed rod-like alginate coated hydroxyapatite nanocrystals with diameter and length of (10 ± 2) nm and (34 ± 7) nm, respectively. Morphological analysis showed that electrospun composite fibers presented a fiber diameter range of (97–170) nm with a greater homogeneity of size distribution and no grain accumulation in 12% PVA fibers containing 0.1% HAL. All the samples showed mechanical strength limits within those expected for bone graft materials but the best tensile strength response among the electrospun scaffolds [(15.2 ± 2.5) MPa] was observed for PVA fiber (12%) containing 0.1% HAL. The swelling ratio of all the composite fibers show that the presence of HAL composites induce a homogeneous swelling throughout the 4-week period, compared to bare fibers. We observe that the presence of HAL composites within the PVA fibers induced a greater degradation rate (54–62) % in one month) compared to PVA bare fibers and we attribute this property to the presence of alginate molecules. Biological assays using human gingival fibroblast cells demonstrated that all the fibrous membranes support cell adhesion and proliferation demonstrating their biocompatibility. The fibers and fibrous scaffolds prepared in the present study show very good morphological and mechanical properties as well as biocompatibility, fundamental conditions for applications as bone graft precursor materials.

Removal of dye and heavy metals from industrial wastewater by activated charcoal-banana rachis cellulose nanocrystal composites filter

ABSTRACT Heavy metal contamination in wastewater has been an issue for the environment and human health nowadays. If these wastewaters are exposed directly to the environment, it will be hazardous for the environment and personal health. So, it is very necessary to treat these ground and surface wastewater before exposing into environment. For this, an effective technique were developed which removed heavy metals from wastewater easily, economically and effectively. The cellulose nano-crystals (CNC) were isolated from banana rachis fibres by a series of chemical treatments as well as 50% H2SO4 hydrolysis successively. On the other hand, raw Indonesian type’s bituminous coal was collected from Noapara industrial area, Jashore, Khulna and was pyrolysed at 700°C, activated by 2M HCl at 700°C and also carbonised at 500°C followed by activation with 30% H3PO4 acid. In this process, adsorbent of modified charcoal-CNC composites was used for the removal of methyl orange dye and five heavy metals, such as Ni(II), Pb(II), Cr(III), Cd(II) and Co(II)), from wastewater and the uptake capacity, selectivity and removal efficiency were also discussed. The filtering efficiency of wastewater purifications were characterised by FTIR, X-RD, TGA, SEM analysis. Finally, wastewater solution and the filtrates solutions were characterised by UV-Vis, and AAS techniques.

Synthesis of PtCuFe alloy nanoframes with high-index facets for efficient electro-oxidation of liquid fuels

By controlling the structure, surface and composition of Pt-based ternary alloy nanocrystals, the electro-catalytic performances of Pt-based catalysts can be improved effectively. In this paper, a one-pot method for synthesis of PtCuFe nanoframes (PtCuFe NFs) with tunable structure and defect density is reported. By controlling the heating mode and the type of ligand, then changing the nucleation/growth kinetics, two types of PtCuFe NFs were obtained. These types of catalysts exhibited excellent electro-catalytic performance for methanol electrooxidation (MOR) and formic acid electrooxidation (FAOR). Specifically, the dendritic nanoframes (d-NFs) showed high electro-catalytic activity for MOR and FAOR, which were 8.34 times and 3.68 times higher than commercial Pt/C, respectively. The stability was also greatly improved. The excellent electrocatalytic activity of PtCuFe NFs is attributed to the defect sites of high-index facets and open framework structures. This strategy provides a new idea for improving the electrocatalytic performance of Pt-based catalysts.

Improved thermoelectric performance of nanostructured Bi2Te3 fabricated by solvent-free mechanical alloying

Thermoelectric materials convert waste heat energy efficiently to electricity in an eco-friendly manner. Bi2Te3 is a known thermoelectric material, which can convert waste heat and solar energy into electricity in the 200–400 K temperature range. Bi2Te3 nanocrystals are prepared in powder form by solvent-free mechanical alloying of elemental Bi and Te powder mixtures under an inert Ar atmosphere. The crystallite size and composition of the Bi2Te3 nanocrystals are analyzed using X-ray diffraction, field-emission scanning electron microscope and energy-dispersive X-ray spectroscopy. Thermal and electrical behaviours and the effect of thermal annealing are studied on the 10 h ball-milled sample in a physical properties measurement system in the 30–375 K temperature range. It is observed that the high-temperature thermal annealing induces significant grain growth, reduces lattice strain, along with a reduction of bandgap energy of the mechanically alloyed Bi2Te3 nanostructures. Thermoelectric properties and the figure of merit of the nanostructures have improved significantly upon thermal annealing. Enhanced thermoelectric performance of the annealed nanostructures has been explained considering the change in their thermal conductivity, electrical resistivity, and crystallite size induced by thermal treatment.