Oxide Core Shell Nanostructures Research Articles

Stable Magnetite@La-Fe Oxide Core-Shell Nanostructures Prepared via Lattice Lock for Reusable Extraction of Phosphate Anions.

Stable magnetic core-shell nanostructures are developed by lattice locking lanthanide-iron (La-Fe) oxide shells with magnetite cores to prevent the release of La from the surfaces of the magnetite nanostructures. The resulting core-shell nanostructures demonstrate excellent outstanding regeneration performance and high adsorption capacity for phosphate (115 mg P·g-1). These nanostructures release minimal La from the magnetite core surfaces after adsorbent regeneration, with a La loss of only 20% compared to the control sample, Mag@La(OH)3. La3+ ions were released at concentrations ranging from 1 to 2.3 μg·L-1 at pH levels of 4 to 8, which is within the metal content range found in natural aquatic environments. These results demonstrate the high stability of the nanostructures after regeneration. Furthermore, the adsorbent exhibits high extraction capacity across a wide pH range of 4 to 10 and performs well even in the presence of interfering anions at phosphate-to-anion molar ratios of 1:5, 1:25, and 1:100. Microscopic and spectroscopic analyses reveal that the primary extraction mechanism of phosphate in the La-containing shells is surface precipitation. This approach not only improves the use of magnetic core-shell nanostructures as adsorbents but also demonstrates the creation of a broad range of stable magnetic functional materials for diverse applications.

Polyimide impregnated silver nanowire-titanium oxide core–shell nanostructures as ultra-stable flexible transparent electrode for multiple applications

Silver nanowires (AgNWs)-based flexible-transparent conducting electrode (f-TCE) have various optoelectronic applications. Although, bare AgNW-based f-TCE faces challenges of poor adhesion with the substrate, rough surface and low thermal stability. In this work, we demonstrate preparation of f-TCE by coating a very thin layer of TiO2 over AgNWs to form AgNW-TiO2 core–shell structures. Due to very thin TiO2 film in core–shell structure, the amorphous TiO2 converted into crystalline and delivered excellent conductivity at low curing temperature of 100 °C. The adhesion and roughness issues are solved by impregnating the core–shell AgNW-TiO2 within polyimide (PI) matrix. The PI impregnated AgNW-TiO2 core–shell structure as f-TCE delivered excellent stability after 5000 times of bending and number of peeling off cycles. The as prepared f-TCE delivered sheet resistance (Rs) of 8.61 Ω/sq with transmittance of 85 % at 550 nm and Rs of 4.2 Ω/sq with transmittance of 81 % when cured at 250 °C. The surface temperature of f-TCE was found to increase up to 90 °C in 40 s after applying 4 V of supply indicating its potential as transparent heater. In addition to that the CIGS solar cell fabricated by utilization of our f-TCE exhibited efficiency of 9.6 %, demonstrating its applicability for photovoltaic applications.

High–performance water electrolyzer with minimum platinum group metal usage: Iron nitride–iridium oxide core–shell nanostructures for stable and efficient oxygen evolution reaction

To reduce the usage of rare-earth metals in a proton-exchange-membrane water electrolyzer (PEMWE), a highly active water-oxidizing anode based on a core–shell catalyst structure was developed. Earth-abundant metal-based iron-nitride nanostructure was adopted to support thin, electrodeposited iridium-oxide films. PEMWEs with core–shell nanostructure has substantially low ohmic and mass-transfer resistances, suggesting that the introduction of Fe2N nanostructure on Ti PTL enhances the transfer of protons, water, and oxygen on the catalyst layer. Furthermore, a high Ir mass activity of 103 A/mgIr was achieved with reduced Ir loading of 0.036 mg/cm2 on the Ti PTL. The well-known weakness of transition-metal nitrides (TMNs) for use in PEMWEs, that is, their chemical instability in corrosive acidic environments, was overcome by carefully passivating the surfaces of the TMNs with chemically stable Ir catalyst layers. As a result, the prepared core–shell-structured catalysts were stable under the PEMWE operating condition.

Gold-coated iron oxide core–shell nanostructures for the oxidation of indoles and the synthesis of uracil-derived spirooxindoles

Synthesis of isatins and uracil-based spirooxindoles catalysed by Au/Fe3O4core–shell nanoparticles under mild conditions and low reaction times.

Copper oxide@cobalt oxide core–shell nanostructure, as an efficient binder-free anode for lithium-ion batteries

Here, cobalt oxide nanostructures synthesized on vertically aligned copper oxide nanowires (NWs) have been investigated as a possible anode material for Lithium-ion batteries (LIBs). Copper oxide NWs were formed by thermal oxidation of electrochemically deposited copper on the stainless steel mesh substrate. The process used allows the formation of highly dense copper oxide NWs with excellent adhesion to the conductive current collector substrate. A simple hydrothermal method was implemented for the deposition of cobalt oxide nanostructures on the copper oxide NWs. The as-prepared binder-free copper oxide@cobalt oxide NWs electrode exhibits a high initial specific capacity of 460 mAh g−1 at a current density of 148 mA g−1. The fabricated core–shell structure effectively improved the capacity of the fabricated half-cell by four times after 30 cycles, compared with bare copper oxide NWs. In addition to its straightforward and inexpensive synthesis process, the improved electrochemical performance suggests the copper oxide@cobalt oxide NWs electrode as a potential anode material for advanced LIBs.

Core and dopant effects toward hydrogen gas sensing activity using Pd@N-CeO2 core–shell nanoflatforms

Developing efficient and stable hydrogen gas sensors may be of urgent demand for its safety uses. Herein, Pd@N-CeO2 core–shell nanoflatforms (CSNFs) are fabricated and utilized for this purpose. The resulting Pd@N-CeO2 CSNFs offer small particle sizes with high Brunauer–Emmett–Teller (BET) surface area and porous nanostructures. The core–shell sensors establish high hydrogen sensing response and fast response and recovery times at a lower optimal working temperature compared to undoped and doped CeO2 ones. In addition, it further demonstrates high selectivity and stability toward hydrogen gas among interfering different target gases. The hydrogen gas sensing betterment is synergistically assigned to Pd core, N dopant, and high BET surface area effects, which decidedly modulate the electrical resistance of core–shell sensors to improve overall gas sensing performance accordingly. Our finding provides an efficient way to design and fabricate versatile hydrogen gas sensors based on metal@nitrogen doped-semiconductor oxide core–shell nanostructures.

Magneto-luminescent zinc/iron oxide core-shell nanoparticles with tunable magnetic properties

Abstract Core-shell nanospheres with tailorable magnetic properties and strong luminescence promise versatile and efficient biomedical and electronic applications. We report a low-cost sonochemical synthesis of ZnO/iron oxide core-shell nanostructures with tunable magnetic properties. The high-resolution transmission electron microscopy (HRTEM) illustrates the distinguished dispersity of the oxide nanoparticles, whereas elemental profiling using line scan data confirm the formation of the distinguished core and shell phases. Annealing in N2–H2 and Ar–H2 ambient alters the magnetic properties such as coercive field, saturation magnetization, and remnant magnetization within the inverse spinel iron oxide with space group Fd3m. Subtle structural changes between maghemite (γ-Fe2O3) and its reduced form, magnetite (Fe3O4), have been identified in the thin (0.5–3 nm) shell region of atomic dimensions. Structural composition including phase transitions and defect states are investigated using XRD, XPS, and Raman measurements. Coexistence of ferromagnetism (from the shell and characterized by magnetic measurements) and strong luminescence (from ZnO core and obtained from photoluminescence spectroscopy) at room temperature indicates exotic magneto-optical coupling, which is supported by the blue-shifted luminescence spectra. Our approach combining nanotechnology and solid-state chemistry opens a new frontier to the building of innovative nanomaterials for integration, especially multifunctional core-shell oxide nanomaterials.

High Entropy Intermetallic–Oxide Core–Shell Nanostructure as Superb Oxygen Evolution Reaction Catalyst

AbstractDesigning active, stable, yet low cost electrocatalysts for the oxygen evolution reaction (OER) is pivotal to the next generation energy storage technology. However, conventional OER catalysts are of low electrochemical efficiency while the state‐of‐the‐art nanoparticle‐based catalysts require mechanical supports, thereby limiting their wide deployment. Here, it is demonstrated that, due to the excellent corrosion resistance of the Fe–Co–Ni–Cr–Nb high entropy intermetallic Laves phase, fabricating a high entropy bulk porous nanostructure is possible by dealloying the corresponding eutectic alloy precursor. As a result, a core–shell nanostructure with amorphous high entropy oxide ultrathin films wrapped around the nanosized intermetallic ligaments is obtained, which together, exhibits an extraordinarily large active surface area, fast dynamics, and superb long‐term durability, outperforming the existing alloy‐ and ceramic‐based OER electrocatalysts. The outcome of the research suggests that the paradigm of “high entropy” design can be used to develop high performance catalytic materials.

Carbon-Encapsulated Metal/Metal Carbide/Metal Oxide Core–Shell Nanostructures Generated by Laser Ablation of Metals in Organic Solvents

Laser ablation of metal in organic solvents (LAMOS) has been proven to be an efficient technique for one-step synthesis of carbon-encapsulated metal/metal carbide/metal oxide core–shell nanostructures. However, the correlation between the influential factors and the final products, such as composition of the core and crystalline structure of the carbon shell, is still unclear to date; moreover, the precise control of this is full of challenges. Herein, comparative experiments of 16 transition metals (Cu, Ag, Au, Pt, Pd, Ti, V, Nb, Cr, Mo, W, Ni, Zr, Mn, Fe, and Zn) were performed to clarify the panorama of LAMOS, including metal atomization and liquid decomposition into carbon and reductive gases, subsequent metal carbonization, surface precipitation, and metal-catalyzed graphitization to form amorphous and graphitic carbon shells. Importantly, it is found that the carbon solubility in metals and the affinity of metals to oxygen are the critical factors in determining the core composition: (1) inert metal...

Development of graphene capped silicon–silicon oxide core–shell nano-structure: Charge trapping characteristics at the interfaces

Colloidal suspension of nano-dimensional Si–SiOX core–shell has been synthesized by step down mechanical process followed by thermo-chemical treatments. Graphene oxide (GO) has been synthesized by modified hummer's method. A wet chemical in situ co-deposition/reduction technique has been performed in amine rich medium to encapsulate the Si–SiOX core–shell nanostructure by amine functionalized reduced graphene oxide (af-rGO). The presence of silicon nano-crystals and af-rGO in the nanocomposite has been confirmed by Raman, FTIR and XRD studies. Core–shell structure of the nanocomposite has been confirmed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). A simple two terminal device has been fabricated with the synthesized nanocomposite in between two aluminium electrodes on glass substrate. In spite of the symmetric architecture of the device, the current–voltage (I–V) characteristics exhibits an asymmetry in nature, suggesting the formation of rectifying junction at the interfaces. Surface potential mapping has been obtained by Kelvin probe force microscopy (KPFM) to reveal the developed built-in potential at the interfaces. A chemical model has been postulated that assures the formation of dipoles and traps at the respective af-rGO/SiOX and SiOX/Si interfaces. The role of trapped charges has been established by solving Poisson's equation, validated by the trap density estimation from the capacitance–voltage (C–V) curve. This newly developed nano-structure has immense potential in the field of photovoltaics and electronics as a basic building block.

Hierarchical Aerographite 3D flexible networks hybridized by InP micro/nanostructures for strain sensor applications

In the present work, we report on development of three-dimensional flexible architectures consisting of an extremely porous three-dimensional Aerographite (AG) backbone decorated by InP micro/nanocrystallites grown by a single step hydride vapor phase epitaxy process. The systematic investigation of the hybrid materials by scanning electron microscopy demonstrates a rather uniform spatial distribution of InP crystallites without agglomeration on the surface of Aerographite microtubular structures. X-ray diffraction, transmission electron microscopy and Raman scattering analysis demonstrate that InP crystallites grown on bare Aerographite are of zincblende structure, while a preliminary functionalization of the Aerographite backbone with Au nanodots promotes the formation of crystalline In2O3 nanowires as well as gold-indium oxide core-shell nanostructures. The electromechanical properties of the hybrid AG-InP composite material are shown to be better than those of previously reported bare AG and AG-GaN networks. Robustness, elastic behavior and excellent translation of the mechanical deformation to variations in electrical conductivity highlight the prospects of AG-InP applications in tactile/strain sensors and other device structures related to flexible electronics.

Nanostructured semiconducting materials for efficient hydrogen generation

Massive production of hydrogen by water decomposition triggered by a solar light active photocatalyst is a major objective in chemistry and a promising avenue to overcome the global energy crisis. The development of efficient, stable, economically viable and eco-friendly photocatalysts for hydrogen production is a challenging task. This article reviews the use of nanocomposite in three combinations: metal oxide–metal oxide semiconductor, metal–metal oxide semiconductor and metal chalcogenide–metal oxide core–shell nanostructures. These core–shell structures occur in two forms: a simple form where the photocatalyst is either in the core or the shell or in a more complex system where the core–shell structure comprises a co-catalyst deposited on a semiconducting material. We discuss the design, synthesis and development of semiconductor-based nanocomposite photocatalysts for hydrogen production. The major points are the role of catalytic active sites, the chemical nature of sacrificial agents, the effect of light sources, the variable light intensity and the energy efficiency calculation. For TiO2-based nanocomposites, the metal oxide or metal co-catalyst loading of 1.0–3.0 wt% was optimal. TiO2 nanotube–CuO hybrid nanocomposites produce 1,14,000 µmol h−1 $${\text{g}}^{ - 1}_{\text{cat}}$$ , whereas TiO2/Au nanocomposites display 1,60,000 µmol h−1 $${\text{g}}^{ - 1}_{\text{cat}}$$ . For core–shell catalysts, a shell thickness of 2–20 nm was found for the best activity, and its performance is as follows: (a) CdS–NiO system produces around 19,949 µmol h−1 $${\text{g}}^{ - 1}_{\text{cat}}$$ and (b) CuO–Cr2O3 as co-catalyst immobilized on TiO2 system produces around 82,390 µmol h−1 $${\text{g}}^{ - 1}_{\text{cat}}$$ .

Synthesis and characterization of noble metal-titania core-shell nanostructures with tunable shell thickness.

Core–shell nanostructures have found applications in many fields, including surface enhanced spectroscopy, catalysis and solar cells. Titania-coated noble metal nanoparticles, which combine the surface plasmon resonance properties of the core and the photoactivity of the shell, have great potential for these applications. However, the controllable synthesis of such nanostructures remains a challenge due to the high reactivity of titania precursors. Hence, a simple titania coating method that would allow better control over the shell formation is desired. A sol–gel based titania coating method, which allows control over the shell thickness, was developed and applied to the synthesis of Ag@TiO2 and Au@TiO2 with various shell thicknesses. The morphology of the synthesized structures was investigated using scanning electron microscopy (SEM). Their sizes and shell thicknesses were determined using tunable resistive pulse sensing (TRPS) technique. The optical properties of the synthesized structures were characterized using UV–vis spectroscopy. Ag@TiO2 and Au@TiO2 structures with shell thickness in the range of ≈40–70 nm and 90 nm, for the Ag and Au nanostructures respectively, were prepared using a method we developed and adapted, consisting of a change in the titania precursor concentration. The synthesized nanostructures exhibited significant absorption in the UV–vis range. The TRPS technique was shown to be a very useful tool for the characterization of metal–metal oxide core–shell nanostructures.

Facile Synthesis of Upconverting Nanoparticles/Zinc Oxide Core–Shell Nanostructures with Large Lattice Mismatch for Infrared Triggered Photocatalysis

Upconverting nanoparticles/zinc oxide core–shell nanostructures with large lattice mismatch have been synthesized via a facile colloidal solution approach which displays excellent infrared triggered photocatalytic degradation toward rhodamine B (RhB). As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

ChemInform Abstract: Recent Advances in the Synthesis and Application of Photocatalytic Metal—Metal Oxide Core—Shell Nanoparticles for Environmental Remediation and Their Recycling Process

AbstractReview: 234 refs.

Metal-core@metal oxide-shell nanomaterials for gas-sensing applications: a review

With an ever-increasing number of applications in many advanced fields, gas sensors are becoming indispensable devices in our daily life. Among different types of gas sensors, conductometric metal oxide semiconductor (MOS) gas sensors are found to be the most appealing for advanced applications in the automotive, biomedical, environmental, and safety sectors because of the their high sensitivity, reduced size, and low cost. To improve their sensing characteristics, new metal oxide-based nanostructures have thus been proposed in recent years as sensing materials. In this review, we extensively review gas-sensing properties of core@ shell nanocomposites in which metals as the core and metal oxides as the shell structure, both of nanometer sizes, are assembled into a single metal@metal oxide core–shell. These nanostructures not only combine the properties of both noble metals and metal oxides, but also bring unique synergetic functions in comparison with single-component materials. Up-dated achievements in the synthesis and characterization of metal@metal oxide core–shell nanostructures as well as their use in MOS sensors are here reported with the main objective of providing an overview about their gas-sensing properties.

The Synthesis and Characterization of Magnetic Nano Gold and Their Application for Antibody Immobilization

Background: Gold (Au) Fe oxide core-shell nanostructure is a major class of nanoscale material that has attracted a considerable attention due to the biotechnological and biomedical applications and specific properties. Methods: Here we synthesized the magnetite nanoparticles (MNPs) with an average size of 10-12 nm in diameter using the chemical co-precipitation of Fe2+ and Fe3+ in strong alkaline material. Then, an Au coated Fe oxide core-shell nanocomposite with an average diameter of 18-20 nm was produced in the presence of sodium citrate as the reducing agent. The structures of Au shell and magnetic core (AunFe oxide) were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) and fourier transformed infrared spectroscopy (FTIR). Results: Results showed that the NPs were agglomerate-free and shaped regularly, with a narrow sized distribution. The Au-coated Fe oxide NPs exhibited a surface plasmon resonance peak in the range of 500-650 nm with a remarkable peak at 550 nm. Conclusions: Immobilization studies with antibody (Ab) demonstrated that the Au Fe oxide core-shell nanostructure can be used to immobilize Ab, making them valuable for biomedical and biological applications.

Synthesis of Gold@Iron Oxide Core-Shell Nanostructures via an Electrochemical Procedure

Core-shell nanostructures have attracted considerable interest as a new class of nanomaterials due to the fascinating physical and chemical characteristics relative to their single-component counterparts. Herein, a facial and low-cost approach was reported for the synthesis of core-shell nanostructures. By using the citrate-stabilized gold nanoparticles as seeds, the gold@iron oxide nanostructures were prepared via an electroxidation of iron nail at 1.0 V between the electrodes in aqueous solution. Parameters such as reaction time play important roles in growing different shell thicknesses of gold@iron oxide core-shell nanostructures. The appropriate shell thicknesses were further optimized to yield the surface-enhanced Raman scattering effects in Raman molecules.

Synthesis of Gold@Iron Oxide Core-Shell Nanostructures via an Electrochemical Procedure

Core-shell nanostructures have attracted considerable interest as a new class of nanomaterials due to the fascinating physical and chemical characteristics relative to their single-component counterparts. Herein, a facial and low-cost approach was reported for the synthesis of core-shell nanostructures. By using the citrate-stabilized gold nanoparticles as seeds, the gold@iron oxide/oxyhydroxide nanostructures were prepared via an electroxidation of iron nail at 1.0 V between the electrodes in aqueous solution. The possible formation processes were as follows:O2 + 4 e− + 2 H2O → 4 OH− (Cathode)Fe → Fe2+ + 2 e− (Anode)In the presence of dissolved oxygen, 4 Fe2+ + O2 → 4 Fe3+ + 2 O2 − amorphous ferric-oxyhydroxides and/or ferric oxide were obtained as precipitate. Fe3+ + 3 H2O ⇌ Fe(OH)3 + 3 H+ Fe(OH)3 ⇌ FeO(OH) + H2O2 FeO(OH) ⇌ Fe2O3 + H2OGold nanoparticles, then act as seeds for the growth of iron oxide/oxyhydroxide shells during the electrolytic process. Parameters such as pH values, buffer composition and reaction time all play important roles in growing different shell thicknesses of gold@iron oxide core-shell nanostructures. The appropriate shell thicknesses were further optimized to yield the greatest surface-enhanced Raman scattering (SERS) effects in Raman molecules. Together, an efficient and reproducible method has been developed to control the shell thicknesses of gold@iron oxide/oxyhydroxide nanostructures. The integration of SERS reporters onto the single gold@iron oxide/oxyhydroxide nanoparticle also allows effective imaging in complex biological system.Two iron nails were inserted into the gold nanoparticles solution (10 mL) as two electrodes placed parallel to each other. Potential of 1.0 V were applied to the electrodes using a direct current (DC) power supply. A detailed illustration of the experimental device was demonstrated in Figure 1. After 0 to 420 min continuous stirring, the anode iron nail corroded, and a gradual growth of a dense shell appeared on each gold nanoparticle. The solution was then centrifuged at 1,500g for 30 min to remove the free iron oxide/oxyhydroxide precipitate. The obtained core-shell nanoparticles were re-suspended in 1.0 mM citrate buffer (pH 6.8) for further experiments.As depicted in Figure 1, a simple electrochemical setup was used to synthesize the gold@iron oxide/oxyhydroxide core-shell nanostructures. The iron nails were used as both the anode and cathode, 0.38 mM citrate buffer (pH 4.3) as the electrolyte. With the reaction time increases from 0 to 420 min, the shell coating proceeds. The surface plasmon resonance peaks of the core-shell nanoparticles became more prominent and red-shifted form 530 nm to 560 nm (Figure 2A). Transmission electron microscopic (TEM) images in Figure 2B further confirm the as-synthesized core-shell structures. The diameter of the gold core was about 49 nm, while the shell thickness was 0, 5, 10, 13, and 16 nm through adjusting the reaction time, respectively. The lattice spacing of the core structure in HRTEM was around 0.22 nm, corresponding to Au (111) fcc planes. These nanoparticles were coated with an amorphous layer on their surface. The iron oxide/oxyhydroxide shell structure was characterized by XPS analysis (data not shown).Due to the electromagnetic field enhancement surrounded the metallic surfaces under laser excitation, gold nanoparticles are very attractive SERS substrates. Figure 3 shows the SERS spectrum of 2-naphthalenethiol (NTP)-labeled gold nanoparticles (Au-NTP). In the experiments, the laser at 785nm was used as an excitation light. All the SERS signals are characteristic of the NTP molecules on the gold substrates. After the deposition of the outer iron oxide/oxyhydroxide shell, SERS signals were retained well after the introduction of the amorphous shell on the NTP-labeled gold nanoparticles.In conclusion, we have demonstrated a facile synthesis route for the preparation of gold@ iron oxide/oxyhydroxide core-shell nanostructures. With the incorporation of SERS reporter, these nanocomposites displayed good SERS performance, which has great potential for multiplexed imaging in living cellsThis work was supported by National Tsing Hua University (101N7046E1) and the Ministry of Science and Techonology (NSC 102-2113-M-007-005-MY3, 102-2627-M-007-006-) of Taiwan, ROC.

Synthesis and Characterization of Core-shell Au Fe Oxide Nanocomposites and Their Application for Detecting Immunological Interaction

Gold (Au) Fe oxide core-shell nanostructure is a major class of nanoscale materials that has attracted considerable attention due to its biotechnological and biomedical applications and properties. Here we synthesized magnetite nanoparticles (MNPs), an average size of 10-12 nm in diameter, using the chemical co-precipitation of Fe2(+) and Fe3(+) in strong alkaline material. Then, an Au-coated Fe oxide core-shell nanocomposite with an average diameter of 18-20 nm was produced in the presence of sodium citrate as the reducing agent. The core-shell structure and the presence of the Fe and Au phases have been confirmed by transmission electron microscopy (TEM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The Au-coated Fe oxide NPs can be used as a carrier in digoxin immunoassays. The concentration of anti-digoxin antibody (Ab) immobilized on the NPs was 30 μg/mg. In order to validate the quality of the Au-coated Fe oxide NPs as immunoassay carriers, an immunoassay system was developed. The relative amount of anti-digoxin Ab immobilized on the NPs was determined by enzyme linked immunosorbent assay (ELISA). Immobilization studies with Ab demonstrated that the Au Fe oxide core-shell nanostructure can be used to immobilize Ab, making them valuable for biomedical and biological applications.