Hybrid Nanocrystals Research Articles

Electroactive γ-Phase, Enhanced Thermal and Mechanical Properties and High Ionic Conductivity Response of Poly (Vinylidene Fluoride)/Cellulose Nanocrystal Hybrid Nanocomposites.

Cellulose nanocrystals (CNCs) were incorporated into poly (vinylidene fluoride) (PVDF) to tailor the mechanical and dielectric properties of this electroactive polymer. PVDF/CNC nanocomposites with concentrations up to 15 wt.% were prepared by solvent-casting followed by quick vacuum drying in order to ensure the formation of the electroactive γ-phase. The changes induced by the presence of CNCs on the morphology of PVDF and its crystalline structure, thermal properties, mechanical performance and dielectric behavior are explored. The results suggest a relevant role of the CNC surface −OH groups, which interact with PVDF fluorine atoms. The real dielectric constant ε’ of nanocomposites at 200 Hz was found to increase by 3.6 times up to 47 for the 15 wt.% CNC nanocomposite due to an enhanced ionic conductivity provided by CNCs. The approach reported here in order to boost the formation of the γ-phase of PVDF upon the incorporation of CNCs serves to further develop cellulose-based multifunctional materials.

Nanointerface Chemistry: Lattice-Mismatch-Directed Synthesis and Application of Hybrid Nanocrystals.

In the past decades, great strides have been made in the synthesis of hybrid nanocrystals (HNCs) consisting of two or more disparate subunits (such as metals and/or semiconductors) joined through nanointerfaces, which are intriguing due to their exceptional functionalities that cannot be achieved by single-component nanosystems. The promising and versatile applications of these HNCs are closely dependent on the structural and electronic properties of the nanointerface between subunits. This is because the compatibility of the lattice structures between subunits not only determines the synthetic accessibility and growth mechanisms of the HNCs on the thermodynamic basis but also influences their interfacial characteristics (atomic arrangement, lattice mismatch-induced strain or defects), configurations, crystallinity, and the synergistic interplay of different subunits at the nanoscale. As a result, nanointerface chemistry has attracted intense scientific endeavors worldwide and spurred the rapid development of the lattice-mismatch-directed precise synthesis. This review gives an overview of the main strategies developed for delicate design and fabrication of core-shell HNCs under different degrees of lattice mismatch (from 0.2% to larger than 50%), including epitaxial seeded growth, nanoscale cation exchange, cation exchange-facilitated nonepitaxial growth, etc. Moreover, as for the core-shell HNCs with small (<5%) or moderate lattice mismatch (∼5-20%), the significance of the lattice-strain control at the nanointerface in maneuvering their functions toward desired applications are discussed in detail. Regarding the core-shell HNCs with large lattice mismatch (>20%), the challenges in precise synthesis, the promising solutions enabled by cation exchange-facilitated nonepitaxial growth, and the enhanced applications of the resulting HNCs with strain-free nanointerface are elaborated. We conclude with a personal perspective on the significance and urgency of fully harnessing the effects of lattice mismatch to further advance the science of synthesis and application of HNCs.

Multi-phase induced ultra-broad 1100-2100 nm emission of Ni2+ in nano-glass composites containing hybrid ZnGa2O4 and ZnF2 nanocrystals

A new type of Ni2+-doped dual-phase glass ceramics (GCs) is developed by a simple one-step thermal-induced crystallization process. The GCs thus obtained are embedded simultaneously with hybrid ZnGa2O4 and ZnF2 nanocrystals (NCs). When pumped by a readily available 808 nm laser diode, an ultra-broad near-infrared (NIR) emission in a range of 1100−2100 nm is observed at room temperature. The NIR emission band with a full-width-at-half-maximum (FWHM) of more than 450 nm is comparable to the largest value ever reported in Ni2+-doped GCs, and much broader than those of single-phase GCs embedded with either pure ZnGa2O4 or ZnF2 NCs. The microscopic morphologies of the embedded hybrid NCs, and especially the distribution of Ni2+ in the dual-phase GCs are studied by analytical transmission electron microscopy (TEM). The intriguing photoluminescence properties of Ni2+ are thoroughly investigated by steady-state and time-resolved emission spectra. The GCs demonstrated herein hold promise as broadband solid-state NIR-light sources.

Ligand-mediated formation of Cu/metal oxide hybrid nanocrystals with tunable number of interfaces.

Combining domains of different chemical nature within the same hybrid material through the formation of heterojunctions provides the opportunity to exploit the properties of each individual component within the same nano-object; furthermore, new synergistic properties will often arise as a result of unique interface interactions. However, synthetic strategies enabling precise control over the final architecture of multicomponent objects still remain scarce for certain classes of materials. Herein, we report on the formation of Cu/MOx (M = Ce, Zn and Zr) hybrid nanocrystals with a tunable number of interfaces between the two domains. We demonstrate that the organic ligands employed during the synthesis play a key role in regulating the final configuration. Finally, we show that the synthesized nanocrystals serve as materials platforms to investigate the impact of the Cu/metal oxide interfaces in applications by focusing on the electrochemical CO2 reduction reaction as one representative example.

Silicon nanocrystal hybrid photovoltaic devices for indoor light energy harvesting.

Silicon nanocrystals (SiNCs) featuring size-dependent novel optical and electrical properties have been widely employed for various functional devices. We have demonstrated SiNC-based hybrid photovoltaics (SiNC-HPVs) and proposed several approaches for performance promotion. Recently, owing to the superiorities such as low power operation, high portability, and designability, organic photovoltaics (OPVs) have been extensively studied for their potential indoor applications as power sources. SiNCs exhibit strong light absorption below 450 nm, which is capable of sufficient photocurrent generation under UV irradiation. Therefore, SiNC-HPVs are expected to be preferably used for energy harvesting systems in indoor applications because an indoor light source consists of a shorter wavelength component below 500 nm than solar light. We successfully demonstrated SiNC-HPVs with a PCE as high as 9.7%, corresponding to the output power density of 34.0 μW cm−2 under standard indoor light irradiation (1000 lx). In addition, we have found that SiNC defects working as electron traps influence the electrical properties of SiNCs substantially, a thermal annealing process was conducted towards the suppression of defects and the improvement of the SiNC-HPVs performance.

Hierarchical Reinforcing Fibers for Energy Harvesting Applications - A Strength Study

This work is concerned with the study of the strength of nanocoated reinforcing fibers. In more detail, glass fibers were coated with an efficient thermoelectric (TE) ink in order to create multifunctional reinforcing fibers for advanced composite structural applications. The main scope is to evaluate the fracture properties of the TE-enabled hierarchical glass fibers. The hybrid nanocrystal TE ink was synthesized via a solvothermal reaction and further fully characterized in coating form. The morphology and wetting properties of the TE ink deposition onto glass fibers were evaluated via SEM and contact angle measurements. Enhanced values by 19.4% in tensile strength for the coated glass fibers compared to the reference are being reported, measured at single fiber level. The evaluated multifunctional glass fiber strength will be utilised during ongoing research for the interfacial shear strength determination.

Preparation of polyimide/BaTiO3‐nanocrystal hybrid thin films and their dielectric property

High dielectric constant is highly desirable in capacitors and memory devices. In this work, oleic acid (OA)‐capped BaTiO3 nanocrystals were synthesized by a two‐phase approach. Polyimide (PI)/BaTiO3‐nanocrystal composite thin films with high dielectric constant have been successfully fabricated. The morphologies and dielectric properties of the hybrid films were exploited. The results showed that BaTiO3 nanocrystals can be uniformly dispersed in the PI thin films owing to the surface modification of OA‐capped BaTiO3 nanocrystals. It was found that the dielectric constant of composite film varies with the volume fraction of BaTiO3 nanocrystals and sintering temperatures and reaches a maximum value of 44.1, which is around 13 times higher than that of pristine PI thin film (3.2). These results demonstrated that PI/BaTiO3‐nanocrystal composite films have considerable application potential in microelectronic fields.

Roles of surfactant and polymer in drug release from spray-dried hybrid nanocrystal-amorphous solid dispersions (HyNASDs)

We prepared hybrid nanocrystal–amorphous solid dispersions (HyNASDs) to enhance the dissolution of a poorly soluble drug, griseofulvin (GF), and elucidated the roles of a surfactant, sodium dodecyl sulfate (SDS), and two polymers, HPC and Soluplus. Wet-milled suspensions containing 1:1 to 1:5 GF:polymer mass ratios, with and without SDS, were spray-dried. HyNASD formation was confirmed via DSC, XRPD, and Raman spectroscopy. In dissolution tests, due to its sub-ambient glass transition temperature, poor miscibility with GF, its inability to inhibit GF recrystallization, HPC provided HyNASDs with low supersaturation capability (≤50%) even at the highest loading (1:5) with/without SDS. Contrarily, owing to its stronger intermolecular interactions–miscibility with GF, and its kinetic solubilization–inhibition of GF recrystallization observed in desupersaturation tests, Soluplus, with SDS, in HyNASDs achieved remarkably high supersaturation (>250%). SDS provided enhanced wettability, allowing for fast supersaturation from Soluplus-based HyNASDs (~300% within 20 min), while higher Soluplus loading led to higher supersaturation.

Ag–TiO2 Hybrid Nanocrystal Photocatalyst: Hydrogen Evolution under UV Irradiation but Not under Visible-Light Irradiation

We report a thermolytic reduction of silver precursors in the presence of anatase TiO2 nanorods to form Ag–TiO2 hybrid nanocrystals (HNCs). Upon changing the reaction conditions, the size and numbe...

Salubrious effects of a vermiculite-cellulose-based bionanocomposite on oxidative stress indices and histomorphology of male Wistar rats.

There is a current interest from the food packaging, biomedical and agricultural sectors in hybrid materials formed from clays and natural polymeric compounds. However, research investigating the toxicity of vermiculite-cellulose nanocrystal (VERN) hybrid on the testes of Wistar rats is rare. Twenty rats, divided into control and treatment groups, were orally administered distilled water, 5, 10, and 20mg/kg bw VERN daily for two consecutive weeks. At the termination of experiments, the testicular organo-somatic index, superoxide dismutase, catalase, and gamma-glutamyl transferase activities were not significantly changed by VERN relative to the controls. Contrarily, myeloperoxidase, glutathione peroxidase, and malondialdehyde levels were depleted in the testes of treated rats. Moreso, VERN increased follicle-stimulating and luteinizing hormones, and decreased testosterone levels at the 20mg/kg dose. Histology of the testes revealed healthy looking Leydig cells at the doses of 5 and 10mg/kg VERN. Overall, these results indicate that oral exposure of VERN was not overly deleterious to the redox and structural histoarchitecture in the testes of rats.

Molybdenum hybrid – Nanocrystals supported on modified Laponite composite as superior catalyst for vapour phase hydrodeoxygenation of clove oil

Valorisation of bio-oil to sustainable energy through hydrodeoxygenation process has been attracted much attention in the development of bio-refineries. The present work emphasizes on the development of a highly active heterogeneous catalyst for hydrodeoxygenation reaction with modified Laponite-γ-alumina and SBA-15 – γ-alumina composites as support for Mo and NiMo catalysts using Mo–inorganic–organic hybrid nanocrystals (HNCs) prepared under hydrothermal condition. The synthesized catalysts were characterised using N2–physisorption, XRD, FT–IR, Raman, HRTEM, TPD/TPR, H2 pulse chemisorption and XPS techniques. The catalysts were evaluated for HDO of eugenol (Lignin model compound, Clove oil) at 400 °C under atmospheric pressure. The physicochemical characterization of the support composites revealed that Mo-HNC supported on modified Laponite exhibited extraordinary stability, metal-support interaction and metal dispersion over the support. The catalytic activity results revealed that the Laponite composite supported NiMo-HNC catalyst performed complete conversion of eugenol with enhanced % selectivity to 3- and 4-propyl phenol (mono-deoxygenated products) and to benzene and 4-propyl cyclohexene (complete deoxygenated products). Thereby, a new Mo-HNC supported modified Laponite composite catalyst has been successfully developed. The role of the HNC-Mo preparation method, textural properties, morphology of Laponite composite catalysts have been demonstrated for efficient HDO of clove oil.

Hybrid nanocrystal–amorphous solid dispersions (HyNASDs) as alternative to ASDs for enhanced release of BCS Class II drugs

A major shortcoming of drug nanocomposites as compared with amorphous solid dispersions (ASDs) is their limited supersaturation capability in dissolution media. Here, we prepared drug hybrid nanocrystal–amorphous solid dispersions (HyNASDs) and compare their performance to ASDs. A wet-milled griseofulvin (GF, BCS II drug) nanosuspension and a GF solution, both containing the same dissolved polymer–surfactant (SDS: sodium dodecyl sulfate) with 1:1 and 1:3 GF:polymer mass ratios, were spray-dried. Hydroxypropyl cellulose (HPC) and Soluplus (Sol) were used as matrix-forming polymers. XRPD, DSC, and Raman spectroscopy reveal that ASDs were formed upon spray-drying the solution-based feed, whereas nanocomposites and nanocomposites with >10% amorphous content, HyNASDs, were formed with the nanosuspension-based feed. Sol provided higher GF relative supersaturation, up to 180% and 360% for HyNASDs and ASDs, respectively, in the dissolution tests than HPC (up to 50% for both) owing to Sol’s stronger intermolecular interactions and miscibility with GF and its recrystallization inhibition. Besides the higher kinetic solubility of GF in Sol, presence of GF nanoparticles vs. micron-sized particles in the nanocomposites enabled fast supersaturation. This study demonstrates successful preparation of fast supersaturating (190% within 20 min) HyNASDs, which renders nanoparticle formulations competitive to ASDs in bioavailability enhancement of poorly soluble drugs.

Ternary Metal Chalcogenides: Into the Exciton and Biexciton Dynamics.

Intra-band-gap state-induced low-toxicity colloidal I-III-VI ternary metal chalcogenide nanocrystals (NCs) have emerged as promising alternatives to the toxic Cd- and Pb-chalcogenides for different optoelectronic and bioimaging applications. In this Perspective, we provide the primary understanding of the intra-band-gap state-induced photoluminescence (PL) of I-III-VI NCs, specifically CuInS2 and AgInS2, as a function of particle size and composition and correlated with time-resolved PL measurements. The intra-band-gap state-induced ultrafast exciton and biexciton dynamics are discussed in detail to unravel the subpicosecond carrier relaxation dynamics through transient absorption measurement. Furthermore, ultrafast dissociation of the biexciton on Au@CuInS2 hybrid NCs has been revealed to be due to the presence of Au, which has direct relevance to the improvement of the solar cell efficiency. The proper fundamental insight of the ultrafast exciton and biexciton dynamics of these materials will enable utilization of ternary metal chalcogenides in photovoltaic as well as light-emitting devices.

Seeded-Growth Aqueous Synthesis of Colloidal-Stable Citrate-Stabilized Au/CeO2 Hybrid Nanocrystals: Heterodimers, Core@Shell, and Clover- and Star-Like Structures

Well-defined colloidal-stable citrate-stabilized Au/CeO2 hybrid nanocrystals (NCs) with coherent quasi-epitaxial interfaces and unprecedented control of their architectural and morphological charac...

Hybride metall-organic nanoflowers and their applications in biotechnology

Among the variety of modern nanomaterials a special class – nanoflowers can be distinguished. These new nanostructures have induced the interest of scientists due to the topographic features of nanolayers, the special location of which allows a higher surface-to-volume ratio compared to classical spherical nanoparticles. Such topographic structure significantly increases the efficiency of surface reactions for nanoflowers. The main purpose of this type of nanomaterials is their use as enzyme stabilizers. Enzymes are biosystems with high activity and substrate specificity, but their use is limited by certain disadvantages, such as high sensitivity to the environment, low reproducibility of experimental results and requirements for complex purification of the components. To facilitate the functioning of enzymes in various conditions, organicinorganic hybrid nanomaterials have been developed, the name of which indicates that all components of inorganic nanoparticles are associated with organic materials. These nanoparticles have numerous promising applications in catalysis, as biosensors, and for drug delivery. Organic-inorganic hybrid nanoflowers have led to the development of a new branch of chemistry – the chemistry of hybrid nanomaterials, whose research is currently undergoing rapid development. Thus, the study of organic-inorganic hybrid nanocrystals can lead to new creative solutions in the field of chemistry of enzyme systems and the rapid development of bionanomaterials and new branches of biotechnology.

Generation of White Light by Hybridization of Red–Green–Blue–Luminescent Materials

Herein, the fabrication of a white luminescent material with photoluminescence (PL) in the region ranging from 350 to 900 nm is reported. Formation of the luminescent material is achieved simply by the high‐temperature (1100 °C) annealing of silicon‐rich oxide nanowires containing a ZnO phase, which are grown by exposing a Zn film to Si and O plasma generated using a mixture of N2O and SiH4 gases at a low temperature (380 °C). The PL spectral response is easily tuned by varying the mixing ratio of the two gases or the Zn film thickness. The generation of white luminescence can be attributed to the hybridization of Si nanocrystals (red), silicon oxide (green), and ZnO (blue)‐based materials.

Composites of hydrophilic polymers and organic nanocrystals enable enhanced robustness

We describe a new family of composite materials, polymer/organic nanocrystal (ONC) hybrids. These were prepared from soluble ONCs based on perylene diimides (PDI) and water‐soluble polymers (sodium alginate and polyvinyl alcohol). Polymer/ONC films were characterized by optical spectroscopy, electron microscopy, and tensile strength studies. The films show enhanced chemical and mechanical stability due to synergy between the constituents. The hybrid films are stable in both water and organic solvents, unlike the individual components. The ONCs we employed possess nonlinear optical activity (second harmonic generation, SHG); they showed improved photostability (stable SHG under laser light) in the hybrids. Tensile strength enhancement (as high as twofold in the film having just 2.4% ONCs by weight) was observed as revealed by mechanical measurements. Hybrids with aligned ONCs were also prepared using simple extrusion via syringe needle followed by gelation. Employing ONCs in polymeric hybrid materials enables facile fabrication in aqueous media, synergy, chemical, mechanical, and photostability as well as useful photofunction (SHG), introducing a versatile class of composite materials.

Covalent bonding of MnO2 onto graphene aerogel forwards: Efficiently catalytic degradation of organic wastewater

Graphene/α-MnO2 nanocrystals hybrid aerogel (GMA) was designed for catalytic ozonation of rhodamine B (RhB) solution in this study. A novel method was proposed to synthesize this hybrid aerogel in an isopropanol-water system, in contrast to the conventional reaction of potassium permanganate with graphene aerogel, which destroyed the desired structure of graphene. Characterization of the synthesized GMA was carried out by XRD, SEM, TEM, Raman, and BET. It was found that GMA had a porous structure and the needle-like α-MnO2 nanocrystals were doped in the graphene aerogel uniformly. Based on the FTIR and XPS analysis, the α-MnO2 was found to covalently bond with graphene aerogel. The removal efficiency of both RhB and COD was found to be in the following order of Blank< GA < SMA (silica wool with nano MnO2 deposited on it) < GMA(I) < GMA(II) < GMA(III). The degradation rate constant (k) of RhB ozonation catalyzed by GMA was determined to be 1.2–2.3 times higher as compared with that by UV/Ozone. The enhanced catalytic activity of GMA could be attributed to the high dispersibility of the α-MnO2 nanocrystals on graphene and the abundant mesopores (r < 40 nm) in GMA. The higher electron cloud density of the Mn atoms, when supported by graphene aerogel, promoted the generation of HO radicals, thereby resulting in better decomposition performance of GMA than UV/Ozone systems.

Transition state and product diffusion control by polymer–nanocrystal hybrid catalysts

Effective catalysts stabilize specific transition states and control the transport of species to and from catalytically active sites. Enzymes show these traits thanks to their diverse amino acid functional groups encapsulating metal centres, but are limited in the reaction conditions in which they can operate. Realizing a catalyst with this kinetic and transport control that can be used under demanding industrial conditions is challenging. Here, we show a modular approach for the systematic synthesis of polymer–nanocrystal hybrids, where palladium nanocrystals are encapsulated within tunable microporous polymer layers. The polymer chemistry and morphology control the catalytic performance of the metal sites, affecting the transition state for CO oxidation and controlling the transport of CO2 away from the active site. This approach can be applied to other polymer–nanocrystal compositions and catalytic applications, and is therefore expected to have an impact in many areas of catalysis. Encapsulation is an effective strategy to tune metal-catalysed reactions, although its potential has not been fully explored. Here, design principles and advanced understanding of the reactivity of different polymer-encapsulated Pd nanocrystals are provided using CO oxidation as a benchmark reaction.

Template Synthesis of Ternary Hybrid Nanocrystals of CoS/Ag2S-Fe2O3 with Near-infrared Photoluminescence

Template Synthesis of Ternary Hybrid Nanocrystals of CoS/Ag₂S-Fe₂O₃ with Near-infrared Photoluminescence