Nano-sized Building Research Articles

Membranes Coated with Graphene-Based Materials: A Review.

Graphene is a popular material with outstanding properties due to its single layer. Graphene and its oxide have been put to the test as nano-sized building components for separation membranes with distinctive structures and adjustable physicochemical attributes. Graphene-based membranes have exhibited excellent water and gas purification abilities, which have garnered the spotlight over the past decade. This work aims to examine the most recent science and engineering cutting-edge advances of graphene-based membranes in regard to design, production and use. Additional effort will be directed towards the breakthroughs in synthesizing graphene and its composites to create various forms of membranes, such as nanoporous layers, laminates and graphene-based compounds. Their efficiency in separating and decontaminating water via different techniques such as cross-linking, layer by layer and coating will also be explored. This review intends to offer comprehensive, up-to-date information that will be useful to scientists of multiple disciplines interested in graphene-based membranes.

Robust Assembly of Cross-Linked Protein Nanofibrils into Hierarchically Structured Microfibers.

Natural, high-performance fibers generally have hierarchically organized nanosized building blocks. Inspired by this, whey protein nanofibrils (PNFs) are assembled into microfibers, using flow-focusing. By adding genipin as a nontoxic cross-linker to the PNF suspension before spinning, significantly improved mechanical properties of the final fiber are obtained. For curved PNFs, with a low content of cross-linker (2%) the fiber is almost 3 times stronger and 4 times stiffer than the fiber without a cross-linker. At higher content of genipin (10%), the elongation at break increases by a factor of 2 and the energy at break increases by a factor of 5. The cross-linking also enables the spinning of microfibers from long straight PNFs, which has not been achieved before. These microfibers have higher stiffness and strength but lower ductility and toughness than those made from curved PNFs. The fibers spun from the two classes of nanofibrils show clear morphological differences. The study demonstrates the production of protein-based microfibers with mechanical properties similar to natural protein-based fibers and provides insights about the role of the nanostructure in the assembly process.

Constitutionally Selective Dynamic Covalent Nanoparticle Assembly.

The future of materials chemistry will be defined by our ability to precisely arrange components that have considerably larger dimensions and more complex compositions than conventional molecular or macromolecular building blocks. However, exerting structural and constitutional control in the assembly of nanoscale entities presents a considerable challenge. Dynamic covalent nanoparticles are emerging as an attractive category of reaction-enabled solution-processable nanosized building block through which the rational principles of molecular synthetic chemistry can be extended into the nanoscale. From a mixture of two hydrazone-based dynamic covalent nanoparticles with complementary reactivity, specific molecular instructions trigger selective assembly of intimately mixed heteromaterial (Au–Pd) aggregates or materials highly enriched in either one of the two core materials. In much the same way as complementary reactivity is exploited in synthetic molecular chemistry, chemospecific nanoparticle-bound reactions dictate building block connectivity; meanwhile, kinetic regioselectivity on the nanoscale regulates the detailed composition of the materials produced. Selectivity, and hence aggregate composition, is sensitive to several system parameters. By characterizing the nanoparticle-bound reactions in isolation, kinetic models of the multiscale assembly network can be constructed. Despite ignoring heterogeneous physical processes such as aggregation and precipitation, these simple kinetic models successfully link the underlying molecular events with the nanoscale assembly outcome, guiding rational optimization to maximize selectivity for each of the three assembly pathways. With such predictive construction strategies, we can anticipate that reaction-enabled nanoparticles can become fully incorporated in the lexicon of synthetic chemistry, ultimately establishing a synthetic science that manipulates molecular and nanoscale components with equal proficiency.

Hybrid Inorganic–Organic Luminescent Supraparticle Taggants with Switchable Dual‐Level ID

AbstractTracking and tracing of objects are of paramount importance for realizing a Circular Economy and can be achieved by incorporating micrometer‐scaled luminescent identification (ID) taggants. While established systems are passive, displaying merely an ID feature, for monitoring a products’ life cycle, conscious taggants with stimuli‐triggered switchable ID signals, e.g., to record a recycling step, are desired. Herein, micrometer‐scaled hybrid inorganic–organic taggants with a temperature‐triggered switchable luminescent ID are reported. They are produced by assembling eight different types of organic and inorganic nanoparticles (NPs) via a two‐step spray‐drying process into supraparticles (SPs) with a core–shell structure. This hierarchical structure and well‐balanced mass‐ratios of the utilized nanosized building blocks are key to controlling the occurring coupling effects within SPs, thus, to obtain the switchable ID functionality. Initially, the temperature‐inert inorganic luminescent ID‐level, located in the core, is concealed by a mutable organic ID‐level, emitted by the shell. Upon specific heat treatment, the ID is switched by irreversible quenching of the organic ID‐level, revealing the inorganic ID‐level. Furthermore, both ID‐levels are read out ratiometrically using the same excitation wavelength for their detection. Based on the SPs’ toolbox‐like manufacturing, the ID signals are adjustable to yield the demanded code variety on both ID‐levels.

Cross-Linked Enzyme-Adhered Nanoparticles (CLEANs) for Continuous-Flow Bioproduction.

Nanostructured but micro-sized biocatalysts were created by bottom-up technology using multi-functionalized silica nanoparticles (NPs) as nano-sized building blocks to form cross-linked enzyme-adhered nanoparticles (CLEANs) as robust micro-sized particles with beneficial internal structure and good mechanical properties. Systematic surface modification of NPs with a grafting mixture consisting of organosilanes with reactive (aminopropyl) and inert (e. g., vinyl, propyl, phenyl, or octyl) functions resulted in functional NPs enabling cross-linking agents, such as glutardialdehyde or bisepoxides (glycerol diglycidyl ether, neopentylglycol diglycidyl ether, and poly(propylene glycol) diglycidyl ether), to bind and cross-link enzymes covalently and to form macroporous microparticles. These CLEANs were able to diminish several weaknesses of traditional cross-linked enzyme aggregates as biocatalysts, such as poor mechanical resistance, difficult recovery, and storage, strengthening their use for packed-bed enzyme reactors. Lipase B from Candida antarctica (CaLB) was selected as model enzyme for development of robust CLEANs, which were successfully tested for various industrially relevant applications including a kinetic resolution of a racemic alcohol and the production of various natural fragrance compounds under continuous-flow conditions.

Silver-loaded carbon sphere-in-rod 3D nano-architectures as electrode material for supercapacitors

Carbon spheres (SCs) with hydrophilic shells consisting of nano-sized building blocks are of great interest for the next generation of electrochemical capacitors. In this study, silver-loaded carbon sphere-in-rod 3D architectures were synthesized by in situ hydrothermal carbonization of sucrose and silver nitrate. Silver loading improves the electrical conductivity of the hybrid electrode by developing nanoscale ligaments between the grown SCs. The obtained sphere-in-rod 3D architectures were characterized using field emission scanning electron microscopy, transmission electron microscopy, dynamic light scattering, energy-dispersive X-ray spectroscopy, elemental mapping, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, Thermogravimetric analysis, and Brunauer-Emmett-teller methods. The electrochemical evaluation revealed that silver-loaded carbon sphere-in-rod 3D architectures exhibited high specific capacitance of 421 mF cm−2 at 1 mA cm−2 and wide operating potential window because of being able to work in both negative and positive voltages. The present work demonstrates a green, low-cost, and scalable approach for constructing a hybrid electrode material using saccharide and noble metal building blocks.

Combining nanosized elementary building blocks of soft and hard matter to create strong, damage resistant materials

Creating strong materials at 325 degrees Celsius using particles in the nanometer range that arrange perfectly in supercrystals via self-assembly

Localized surface acetylation of aqueous counter collision cellulose nanofibrils using a Pickering emulsion as an interfacial reaction platform

The self-organization of nano-sized fibrous building blocks is essential for the construction of biomimetic architectonics and hierarchically constructed bio-based materials. The localization of hydrophobic moieties on the surfaces of such nanofibrils is key to hierarchical assembly in aqueous systems. In this study, unique self-assembling fibrous building blocks comprising amphiphilic cellulose nanofibrils (CNFs) were prepared by aqueous counter collision (ACC). The purpose of the study was to control the surface properties of ACC-CNFs by selectively acetylating their surfaces at the oil/water interfaces of a Pickering emulsion. Localized interfacial reactions occurred when the ACC-CNFs were adsorbed onto the surfaces of oil droplets containing the reaction reagents. Such acetylation reactions were achieved whilst maintaining the crystallinity and fibrous morphology of the original CNFs. The surfaces of films cast from the acetylated ACC-CNFs described herein had unique self-aggregation properties that contrasted markedly with those of films cast from acetylated ACC-CNFs prepared in homogenous dispersions.

Discrete Giant Polymeric Chains Based on Nanosized Monomers.

As size-amplified analogues of canonical macromolecules, polymeric chains built up by “giant” monomers represent an experimental realization of the “beads-on-a-string” model at larger length scales, which could provide insights into fundamental principles of polymer science. In this work, we modularly constructed discrete giant polymeric chains using nanosized building blocks (polyhedral oligomeric silsesquioxane, POSS) as basic repeat units through an efficient and robust iterative exponential growth approach, with precise control on molecular parameters, including size, composition, regioconfiguration, and surface functionalities. Their chemical structures were fully characterized by nuclear magnetic resonance spectroscopy, size-exclusion chromatography, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. With elaborately designed amphiphilic block POSS chains and their analogues made of conventional monomers, the size effects were delicately studied and highlighted. Interesting assembly behaviors emerge as a result of distinct interactions and molecular dynamics. This category of molecules shares general self-assembly characteristics as the conventional counterparts in terms of phase transition and evolution. Meanwhile, it turns out that the monomer size has profound impacts on phase stability, as a trade-off between entropic and enthalpic contributions. It may open up a door for modular and programmable design of interesting materials with complex structures and diverse functions.

The Design of Nano/Micro Structure of the Composite Metal Oxides and the Gas Sensing Performances

The gas sensor based on metal oxide semiconductors (MOS), which is known as one of the most widely popular gas sensors, plays an important role in gas detection in all walks of life. The sensing principle of MOS-based gas sensors results from changes in resistance caused by the adsorption–desorption reaction between target gases and chemisorbed oxygen ions on the surface of the sensing layers [1-3]. To generate adjustable oxygen vacancies on the surfaces of MOS is an effective strategy to improve the gas sensing performances [4, 5]. This work reported the synthesis of spinel type cobalt-based MOS (MCo2O4, M=Zn, Ni and Mn) (Fig. 1(a)) and the performance optimization by controlling the stoichiometric proportion of sensing materials. The results show that sensing properties can be significantly enhanced by substituting Co with other transition metals in the lattices. ZnCo2O4 with typical normal spinel structure can be regarded as a representative sensing material among the studied cobaltates, which exhibits the best sensing performances to acetone. The sensitivity of the ZnCo2O4 sensor is 24 and 106 times higher than those of the NiCo2O4-sensor and MnCo2O4-sensor at 190 °C, respectively. Zn substitution in tetrahedrally coordinated positions can provide more adsorbed oxygen molecules and oxygen vacancies and enable a better gas-sensing capability (Fig. 1(b-d)). In addition, the transition metal content can also be adjusted to further increase oxygen vacancy. The Zn content was controlled in ZnxCo3-xO4 bimetallic oxides during the growth process. When tested as an acetone sensing layer for gas sensors, the prepared ZnxCo3-xO4 materials (Zn/Co=0.37) composed of nano-sized building blocks exhibited a response of 35.6 to 200 ppm acetone within 60 s (Fig. 1(e)). In addition, the sensor device also demonstrates a low detection limit of 0.5 ppm to acetone, even in a high humidity environment. The better acetone sensing performance is attributed to the adsorbed oxygen and abundant oxygen vacancies of ZnCo-0.37 samples. More adsorbed oxygen molecules that take part in the sensing reaction are beneficial for the release of a mass of electrons to increase the extent of the change in resistance. Oxygen vacancies, serving as electron donors, endow ZnCo-n nanocages with unpaired electrons to provide free electrons and active sites to enhance the gas sensing properties. This approach sheds light on the rational design of bimetallic oxides with abundant oxygen vacancy and the development of superior sensors targeted for ultratrace acetone gas.

Cellulose nanofibrils and nanocrystals in confined flow: Single-particle dynamics to collective alignment revealed through scanning small-angle x-ray scattering and numerical simulations.

Nanostructured materials made through flow-assisted assembly of proteinaceous or polymeric nanosized fibrillar building blocks are promising contenders for a family of high-performance biocompatible materials in a wide variety of applications. Optimization of these processes relies on improving our knowledge of the physical mechanisms from nano- to macroscale and especially understanding the alignment of elongated nanoparticles in flows. Here, we study the full projected orientation distributions of cellulose nanocrystals (CNCs) and nanofibrils (CNFs) in confined flow using scanning microbeam SAXS. For CNCs, we further compare with a simulated system of dilute Brownian ellipsoids, which agrees well at dilute concentrations. However, increasing CNC concentration to a semidilute regime results in locally arranged domains called tactoids, which aid in aligning the CNC at low shear rates, but limit alignment at higher rates. Similarly, shear alignment of CNF at semidilute conditions is also limited owing to probable bundle or flock formation of the highly entangled nanofibrils. This work provides a quantitative comparison of full projected orientation distributions of elongated nanoparticles in confined flow and provides an important stepping stone towards predicting and controlling processes to create nanostructured materials on an industrial scale.

Electrochemical sensor for detection of mercury (II) ions in water using nanostructured bismuth hexagons

This study presents a systematic observation of the ability of bismuth nanostructures to detect trace amounts of mercury. Nanostructured hexagons of bismuth were synthesized using electrochemical deposition with potentiostatic mode on indium tin oxide-coated glass electrodes. Regular hexagons composed of nano-sized hexagonal building blocks (edge length $$\approx 80$$ to 700 nm) with well-defined edges were observed in scanning electron microscopy studies. X-ray diffraction pattern indicates the presence of polycrystalline bismuth and bismuth oxide in rhombohedral and cubic phases, respectively. X-ray photoelectron spectroscopy was done to analyze the chemical structure of the prepared nanostructures. Square wave anodic stripping voltammetry technique confirms that these nanostructured electrodes are highly sensitive to $$Hg^{2+}$$ ions down to concentrations as low as 0.74 ppb.

Probing enhanced lithium-ion transport kinetics in 2D holey nanoarchitectured electrodes

Nanostructuring has been proved effective towards improving many energy storage and conversion devices, and is feasible for a wide range of materials. In particular, secondary nanoarchitectured materials exhibit collective advantages compared with nano-sized primary building blocks. Despite the manifold efforts in designed nanoarchitectures and synthetic routes, the underlying ion diffusion kinetics and phase transformation behaviors within nanoarchitectures still remain less explored. Herein, we probed enhanced lithium-ion transport behaviors using 2D holey zinc ferrite (ZFO) nanosheets as a model material, to demonstrate how self-assembled 2D holey nanoarchitectured electrodes can feature efficient ion diffusion channels, robust yet continuous electron transfer framework, and enlarged surface area, contributing to the superior performance over the ZFO nanoparticles without secondary structures. By revealing kinetic parameters through combined spectroscopic measurements and electrochemical techniques, our study manifests increased lithium-ion diffusion coefficients, higher capacitive charge storage contribution and reduced charge transfer impedance in holey nanosheets compared to randomly aggregated nanoparticles. Our results promote deeper understanding of significantly enhanced electrochemical energy storage properties of these 2D holey nanoarchitectured electrodes resulted from more uniform and complete phase transformation and better active material utilization.

Dependence of excited-state properties of tellurium on dimensionality: From bulk to two dimensions to one dimensions

The dependence of excited-state properties on dimensionality is the most prominent character of nanostructures. Using first-principles many-body perturbation theory, we show how those excited-state properties, i.e., quasiparticle energies and excitons, evolve with the dimensionality of tellurium nanostructures that have attracted significant interest because of their high carrier mobility and air stability. Even though the elementary atomistic structures are similar, dimensionality dictates many-electron interactions and excited-state properties: the self-energy correction to the band gap is increased from 0.22 eV in bulk to 0.90 eV in a two-dimensional (2D) monolayer, and ultimately to 2.70 eV in a one-dimensional (1D) spiral tube; excitonic effects are weak in bulk with an exciton binding energy less than 10 meV, while the exciton binding energy is substantially enhanced to be 0.67 eV in the monolayer and 2.40 eV in the 1D structure. Interestingly, reduced dimensionality also produces substantial anisotropic optical response through many-electron interactions: local-field effects dominate the optical spectra of 2D and 1D structures and induce highly anisotropic optical responses. These results not only reveal a systematic picture for understanding the evolution of excited-state properties with dimensionality but also suggest the possibility of designing macroscopic electronic and optical properties by engineering nanosized building blocks.

Joining of Individual Silicon Carbide Nanowires Via Proton Beam Irradiation

Background: Joining nanosized building blocks is a promising approach to fabricate functional nanodevices and nanosystems. Nanojoining approach also helps in integrating these nanodevices and nanosystems for the miniaturization of devices. The nanodevices are mainly fabricated by joining metallic and semiconductor nanowires/nanotubes. Objective: Silicon Carbide Nanowires (SiC-NWs) have become important nanomaterials for future nanoscale devices due to their unique physical properties. Method: In this paper, nanowelding of SiC-NWs has been demonstrated using ion beam technology. SiC-NWs were irradiated by 5 MeV proton beam as per SRIM code simulation. Nanojoining of SiC-NWs was confirmed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Conclusion: Joining of individual SiC-NWs by 5 MeV proton beam irradiation was successfully achieved at the contact point as X-, Y-, II-, and T-shaped welded junctions.

A New Label-Free Technique for Analysing Evaporation Induced Self-Assembly of Viral Nanoparticles Based on Enhanced Dark-Field Optical Imaging.

Nanoparticle self-assembly is a complex phenomenon, the control of which is complicated by the lack of appropriate tools and techniques for monitoring the phenomenon with adequate resolution in real-time. In this work, a label-free technique based on dark-field microscopy was developed to investigate the self-assembly of nanoparticles. A bio-nanoparticle with complex shape (T4 bacteriophage) that self-assembles on glass substrates upon drying was developed. The fluid flow regime during the drying process, as well as the final self-assembled structures, were studied using dark-field microscopy, while phage diffusion was analysed by tracking of the phage nanoparticles in the bulk solutions. The concentrations of T4 phage nanoparticles and salt ions were identified as the main parameters influencing the fluid flow, particle motion and, consequently, the resulting self-assembled structure. This work demonstrates the utility of enhanced dark-field microscopy as a label-free technique for the observation of drying-induced self-assembly of bacteriophage T4. This technique provides the ability to track the nano-sized particles in different matrices and serves as a strong tool for monitoring self-assembled structures and bottom-up assembly of nano-sized building blocks in real-time.

Nanosized FexNi2-xP embedded phosphorus-doped carbon nanorods with superior lithium storage performance

Novel hybrid transition metal phosphides with elaborate designed architectures are long pursued to improve their lithium-ion storage properties. Here, nanocomposite of FexNi2-xP particles and P-doped carbon (P-C) substrate has been successfully synthesized through a one-step low-temperature phosphidation of Fe2Ni MIL-88 nanorods. In this nanocomposite, the nano-sized FexNi2-xP particles are embedded into the P-doped carbon nanorods substrate, integrating the high capacity of FexNi2-xP and the excellent conductivity of P-doped carbon together. When used as anode material for lithium-ion batteries, the nanocomposite exhibits a high reversible capacity of 775mAhg−1 after 400 cycles at a current density of 100mAg−1. Even at a high current density of 2000mAg−1, a discharge capacity of 360mAhg−1 could still be maintained. This excellent electrochemical performance may be attributed to the nano-sized building blocks of FexNi2-xP particles and the improved conductivity contributed by P-doped carbon substrate as well as the strong interaction between FexNi2-xP and carbon. Furthermore, this strategy of synthesizing the FexNi2-xP/P-C nanorods with metal-organic frameworks as a starting point can be extended to design other bimetallic transition metal phosphides with superior lithium storage properties.

Spray-drying-assisted reassembly of uniform and large micro-sized MIL-101 microparticles with controllable morphologies for benzene adsorption

Significant research has been focused on the synthesis of metal-organic frameworks (MOFs) with controllable compositions and structures, while much fewer works have been devoted to the construction of large micro-sized MOFs with uniform sizes and morphologies, which could be beneficial for practical applications. In this paper, a unique microfluidic jet spray drying technology has been adopted to reassemble nano-sized MIL-101 building blocks into hierarchical microparticles with uniform and large particle sizes. Specifically, suspension precursors of nano-sized MIL-101 building blocks are atomized into uniform droplets and then converted to microparticles on a one-to-one basis through a fast and scalable spray drying process. The particle size and morphology can be controlled by adjusting the solid concentration of the suspension and the drying temperature. The particle formation process with evolution of different morphologies are discussed. The resultant uniform MIL-101 microparticles possess hierarchical porosities and maintain the intrinsic crystal structure, microporosity and thermal stability of the nano-sized building blocks. They demonstrate a high efficiency toward benzene adsorption from n-octane solutions with high adsorption rates and very high adsorption capacities under batch conditions. Moreover, the large particle size and hierarchical structure make them applicable as filler of a fixed bed for dynamic flow separation of benzene from n-octane solutions with promising performance. The microfluidic jet spray drying technology can also be extended for the reassembly of other uniform MOF microparticles.

Terpenoids as Renewable Nano-Sized Building Blocks

Terpenoids are a large and structurally group of natural products containing multiple five carbon containing isoprene units. Previously we have reported that irrespective of their acyclic or alicyclic nature, all the triterpenoids containing 30C’s have nano-metric lengths. In the current studies, detailed computations have been carried out with 120 naturally occurring mono- (C10), sesqui- (C15), di- (C20), sester- (C25), sesqua- (C35) and tetra- (C40) terpenoids using Gaussian 09 software with Gauss view 07 and molecular mechanics calculation using Serena software. The heat of formation and the calculated molecular lengths obtained by the two methods were compared. Interestingly, monoterpenoid to tetraterpenoid all the terpenoids (except three monoterpenoid and one sesqui-terpenoid) have molecular lengths above one nanometer making them useful as nano-sized building blocks.

Grafting PNIPAAm from β-barrel shaped transmembrane nanopores.

The research on protein-polymer conjugates by grafting from the surface of proteins has gained significant interest in the last decade. While there are many studies with globular proteins, membrane proteins have remained untouched to the best of our knowledge. In this study, we established the conjugate formation with a class of transmembrane proteins and grow polymer chains from the ferric hydroxamate uptake protein component A (FhuA; a β-barrel transmembrane protein of Escherichia coli). As the lysine residues of naturally occurring FhuA are distributed over the whole protein, FhuA was reengineered to have up to 11 lysines, distributed symmetrically in a rim on the membrane exposed side (outside) of the protein channel and exclusively above the hydrophobic region. Reengineering of FhuA ensures a polymer growth only on the outside of the β-barrel and prevents blockage of the channel as a result of the polymerization. A water-soluble initiator for controlled radical polymerization (CRP) was consecutively linked to the lysine residues of FhuA and N-isopropylacrylamide (NIPAAm) polymerized under copper-mediated CRP conditions. The conjugate formation was analyzed by using MALDI-ToF mass spectrometry, SDS-PAGE, circular dichroism spectroscopy, analytical ultracentrifugation, dynamic light scattering, transmission electron microscopy and size exclusion chromatography. Such conjugates combine the specific functions of the transmembrane proteins, like maintaining membrane potential gradients or translocation of substrates with the unique properties of synthetic polymers such as temperature and pH stimuli handles. FhuA-PNIPAAm conjugates will serve as functional nanosized building blocks for applications in targeted drug delivery, self-assembly systems, functional membranes and transmembrane protein gated nanoreactors.