Facile synthesis of δ-MnO2 biotemplated by waste tobacco stem-silks for enhanced removal of Sb(III).

The elimination of antimony pollution has attracted increasing concerns because of its high toxicity to human health and the natural environment. In this work, biomimetic δ-MnO2 was synthesized by using waste tobacco stem-silks as biotemplate (Bio-δ-MnO2) and used in the capture of Sb(III)from aqueous solution. The tobacco stem-silks not only provided unique wrinkled morphologies but also contained carbon element self-doped into the resulting samples. The maximum Sb(III) adsorption capacity reached 763.4 mg∙g -1, which is 2.06 times higher than δ-MnO2 without template (370.0 mg∙g -1), 4.53 times than tobacco stem-silks carbon (168.5 mg∙g -1), and 10.39 times than commercial MnO2 (73.5 mg∙g -1), respectively. The isotherm and kinetic studies indicated that the adsorption behavior was consistent with the Langmuir isotherm model and the pseudo-second-order kinetic equation. As far as we are aware, the adsorption capacity of Bio-δ-MnO2 is much higher than that of most Sb(III) adsorbents. FT-IR, XPS, SEM, XRD, and Zeta potential analyses showed that the main mechanism for the adsorption of Sb(III) by Bio-δ-MnO2 includes electrostatic attraction, surface complexation, and redox. Overall, this study provides a new sustainable way to convert agricultural wastes to more valuable products such as biomimetic adsorbent for Sb(III) removal in addition to conventional activated carbon and biochar.

Cellulose Nanofiber-Alginate Biotemplated Cobalt Composite Multifunctional Aerogels for Energy Storage Electrodes.

Tunable porous composite materials to control metal and metal oxide functionalization, conductivity, pore structure, electrolyte mass transport, mechanical strength, specific surface area, and magneto-responsiveness are critical for a broad range of energy storage, catalysis, and sensing applications. Biotemplated transition metal composite aerogels present a materials approach to address this need. To demonstrate a solution-based synthesis method to develop cobalt and cobalt oxide aerogels for high surface area multifunctional energy storage electrodes, carboxymethyl cellulose nanofibers (CNF) and alginate biopolymers were mixed to form hydrogels to serve as biotemplates for cobalt nanoparticle formation via the chemical reduction of cobalt salt solutions. The CNF-alginate mixture forms a physically entangled, interpenetrating hydrogel, combining the properties of both biopolymers for monolith shape and pore size control and abundant carboxyl groups that bind metal ions to facilitate biotemplating. The CNF-alginate hydrogels were equilibrated in CaCl2 and CoCl2 salt solutions for hydrogel ionic crosslinking and the prepositioning of transition metal ions, respectively. The salt equilibrated hydrogels were chemically reduced with NaBH4, rinsed, solvent exchanged in ethanol, and supercritically dried with CO2 to form aerogels with a specific surface area of 228 m2/g. The resulting aerogels were pyrolyzed in N2 gas and thermally annealed in air to form Co and Co3O4 porous composite electrodes, respectively. The multifunctional composite aerogel's mechanical, magnetic, and electrochemical functionality was characterized. The coercivity and specific magnetic saturation of the pyrolyzed aerogels were 312 Oe and 114 emu/gCo, respectively. The elastic moduli of the supercritically dried, pyrolyzed, and thermally oxidized aerogels were 0.58, 1.1, and 14.3 MPa, respectively. The electrochemical testing of the pyrolyzed and thermally oxidized aerogels in 1 M KOH resulted in specific capacitances of 650 F/g and 349 F/g, respectively. The rapidly synthesized, low-cost, hydrogel-based synthesis for tunable transition metal multifunctional composite aerogels is envisioned for a wide range of porous metal electrodes to address energy storage, catalysis, and sensing applications.

Metallization of Targeted Protein Assemblies in Cell-Derived Extracellular Matrix by Antibody-Guided Biotemplating.

Biological systems are composed of hierarchical structures made of a large number of proteins. These structures are highly sophisticated and challenging to replicate using artificial synthesis methods. To exploit these structures in materials science, biotemplating is used to achieve biocomposites that accurately mimic biological structures and impart functionality of inorganic materials, including electrical conductivity. However, the biological scaffolds used in previous studies are limited to stereotypical and simple morphologies with little synthetic diversity because of a lack of control over their morphologies. This study proposes that the specific protein assemblies within the cell-derived extracellular matrix (ECM), whose morphological features are widely tailorable, can be employed as versatile biotemplates. In a typical procedure, a fibrillar assembly of fibronectin-a constituent protein of the ECM-is metalized through an antibody-guided biotemplating approach. Specifically, the antibody-bearing nanogold is attached to the fibronectin through antibody-antigen interactions, and then metals are grown on the nanogold acting as a seed. The biomimetic structure can be adapted for hydrogen production and sensing after improving its electrical conductivity through thermal sintering or additional metal growth. This study demonstrates that cell-derived ECM can be an attractive option for addressing the diversity limitation of a conventional biotemplate.

Investigating the Effect of Reflectance Tuning on Photocatalytic Dye Degradation with Biotemplated ZnO Photonic Nanoarchitectures Based on Morpho Butterfly Wings.

Photonic nanoarchitectures of butterfly wings can serve as biotemplates to prepare semiconductor thin films of ZnO by atomic layer deposition. The resulting biotemplated ZnO nanoarchitecture preserves the structural and optical properties of the natural system, while it will also have the features of the functional material. The ZnO-coated wings can be used directly in heterogeneous photocatalysis to decompose pollutants dissolved in water upon visible light illumination. We used the photonic nanoarchitectures of different Morpho butterflies with different structural colors as biotemplates and examined the dependence of decomposition rates of methyl orange and rhodamine B dyes on the structural color of the biotemplates and the thickness of the ZnO coating. Using methyl orange, we measured a ten-fold increase in photodegradation rate when the 20 nm ZnO-coated wings were compared to similarly coated glass substrates. Using rhodamine B, a saturating relationship was found between the degradation rate and the thickness of the deposited ZnO on butterfly wings. We concluded that the enhancement of the catalytic efficiency can be attributed to the slow light effect due to a spectral overlap between the ZnO-coated Morpho butterfly wings reflectance with the absorption band of dyes, thus the photocatalytic performance could be changed by the tuning of the structural color of the butterfly biotemplates. The photodegradation mechanism of the dyes was investigated by liquid chromatography-mass spectroscopy.

Synthesis of Fe-TiO2 and Cu-TiO2 Based Materials by Olive Leaves Biotemplating-Application to Hydrogen Production from Glycerol Photoreforming.

Hydrogen production is mainly based on the use of fossil fuels, but currently, many alternative routes are being developed, among which the photo-reforming of oxygenated organic compounds stands out. Recently, several studies have been carried out in order to develop new techniques to create bio-inspired TiO2 structures. One of these is 'biotemplating', a process that replicates a biological system in an inorganic TiO2-based structure. In this study, olive by-products-olive leaves-are valorized as a biotemplate for the synthesis of new Fe-TiO2- and Cu-TiO2-based photocatalysts with the aim of improving the replication of the leaf structure and enhancing hydrogen photoproduction. In conclusion, the incorporation of iron and copper decreases the band gap and increases the energetic disorder at the band edges. Moreover, it is verified by SEM and TEM that the metals are not found forming particles but are introduced into the formed TiO2 structure. The accuracy of the internal and external structure replication is improved with the incorporation of Fe in the synthesis, while the incorporation of Cu substantially improves the production of hydrogen, which is multiplied 14 times under UV light and 6 times under sunlight, as compared to a pure TiO2 structure.

Designing the Self-Assembly of Arbitrary Shapes Using Minimal Complexity Building Blocks.

The design space for self-assembled multicomponent objects ranges from a solution in which every building block is unique to one with the minimum number of distinct building blocks that unambiguously define the target structure. We develop a pipeline to explore the design spaces for a set of structures of various sizes and complexities. To understand the implications of the different solutions, we analyze their assembly dynamics using patchy particle simulations and study the influence of the number of distinct building blocks, and the angular and spatial tolerances on their interactions, on the kinetics and yield of the target assembly. We show that the resource-saving solution with a minimum number of distinct blocks can often assemble just as well (or faster) than designs where each building block is unique. We further use our methods to design multifarious structures, where building blocks are shared between different target structures. Finally, we use coarse-grained DNA simulations to investigate the realization of multicomponent shapes using DNA nanostructures as building blocks.

Spectral Engineering of Hybrid Biotemplated Photonic/Photocatalytic Nanoarchitectures.

Solar radiation is a cheap and abundant energy for water remediation, hydrogen generation by water splitting, and CO2 reduction. Supported photocatalysts have to be tuned to the pollutants to be eliminated. Spectral engineering may be a handy tool to increase the efficiency or the selectivity of these. Photonic nanoarchitectures of biological origin with hierarchical organization from nanometers to centimeters are candidates for such applications. We used the blue wing surface of laboratory-reared male Polyommatus icarus butterflies in combination with atomic layer deposition (ALD) of conformal ZnO coating and octahedral Cu2O nanoparticles (NP) to explore the possibilities of engineering the optical and catalytic properties of hybrid photonic nanoarchitectures. The samples were characterized by UV-Vis spectroscopy and optical and scanning electron microscopy. Their photocatalytic performance was benchmarked by comparing the initial decomposition rates of rhodamine B. Cu2O NPs alone or on the butterfly wings, covered by a 5 nm thick layer of ZnO, showed poor performance. Butterfly wings, or ZnO coated butterfly wings with 15 nm ALD layer showed a 3 to 3.5 times enhancement as compared to bare glass. The best performance of almost 4.3 times increase was obtained for the wings conformally coated with 15 nm ZnO, deposited with Cu2O NPs, followed by conformal coating with an additional 5 nm of ZnO by ALD. This enhanced efficiency is associated with slow light effects on the red edge of the reflectance maximum of the photonic nanoarchitectures and with enhanced carrier separation through the n-type ZnO and the p-type Cu2O heterojunction. Properly chosen biologic photonic nanoarchitectures in combination with carefully selected photocatalyst(s) can significantly increase the photodegradation of pollutants in water under visible light illumination.

Spectral tuning of biotemplated ZnO photonic nanoarchitectures for photocatalytic applications.

The photocatalytic activity of a flat surface can be increased by micro- and nanostructuring the interface to increase the area of the contact surface between the photocatalyst and the solute, and moreover, to optimize charge carrier transfer. Further enhancement can be achieved by using photonic nanostructures, which exhibit photonic band gap (PBG). Structurally coloured butterfly wings offer a rich 'library' of PBGs in the visible spectral range which can be used as naturally tuned sample sets for biotemplating. We used conformal atomic layer deposition of ZnO on the wings of various butterfly species (Arhopala asopia, Hypochrysops polycletus, Morpho sulkowskyi, Polyommatus icarus) possessing structural colour extending from the near UV to the blue wavelength range, to test the effects arising from the nanostructured surfaces and from the presence of different types of PBGs. Aqueous solutions of rhodamine B were used to test the enhancement of photocatalytic activity that was found for all ZnO-coated butterfly wings. The best reaction rate of decomposing rhodamine B when illuminated with visible light was found in 15 nm ZnO coated M. sulkowskyi wing, the reflectance of which had the highest overlap with the absorption band of the dye and had the highest reflectance intensity.

Multiscale Functional Metal Architectures by Antibody-Guided Metallization of Specific Protein Assemblies in Ex Vivo Multicellular Organisms.

Biological systems consist of hierarchical protein structures, each of which has unique 3D geometries optimized for specific functions. In the past decades, the growth of inorganic materials on specific proteins has attracted considerable attention. However, the use of specific proteins as templates has only been demonstrated in relatively simple organisms, such as viruses, limiting the range of structures that can be used as scaffolds. This study proposes a method for synthesizing metallic structures that resemble the 3D assemblies of specific proteins in mammalian cells and animal tissues. Using 1.4 nm nanogold-conjugated antibodies, specific proteins within cells and ex vivo tissues are labeled, and then the nanogold acts as nucleation sites for growth of metal particles. As proof of concept, various metal particles are grown using microtubules in cells as templates. The metal-containing cells are applied as catalysts and show catalytic stability in liquid-phase reactions due to the rigid support provided by the microtubules. Finally, this method is used to produce metal structures that replicate the specific protein assemblies of neurons in the mouse brain or the extracellular matrices in the mouse kidney and heart. This new biotemplating approach can facilitate the conversion of specific protein structures into metallic forms in ex vivo multicellular organisms.

MoSBOTs: Magnetically Driven Biotemplated MoS2 -Based Microrobots for Biomedical Applications.

2D layered molybdenum disulfide (MoS2 ) nanomaterials are a promising platform for biomedical applications, particularly due to its high biocompatibility characteristics, mechanical and electrical properties, and flexible functionalization. Additionally, the bandgap of MoS2 can be engineered to absorb light over a wide range of wavelengths, which can then be transformed into local heat for applications in photothermal tissue ablation and regeneration. However, limitations such as poor stability of aqueous dispersions and low accumulation in affected tissues impair the full realization of MoS2 for biomedical applications. To overcome such challenges, herein, multifunctional MoS2 -based magnetic helical microrobots (MoSBOTs) using cyanobacterium Spirulina platensis are proposed as biotemplate for therapeutic and biorecognition applications. The cytocompatible microrobots combine remote magnetic navigation with MoS2 photothermal activity under near-infrared irradiation. The resulting photoabsorbent features of the MoSBOTs are exploited for targeted photothermal ablation of cancer cells and on-the-fly biorecognition in minimally invasive oncotherapy applications. The proposed multi-therapeutic MoSBOTs hold considerable potential for a myriad of cancer treatment and diagnostic-related applications, circumventing current challenges of ablative procedures.

Synthesis of bioactive glass using cellulose nano fibre template.

This study introduces a templating approach using a cellulosic suspension to create a porous SiO2-CaO-P2O5-Na2O bioactive glass material. Sol-gel approach was used as the synthesis method. Carbon nanofibers in suspension form was used as the templating material. The amount of CNF used in the experiment ranged from 5% to 25% by volume. The morphology, porosity, crystallinity of the combeite phase, mechanical and chemical properties of the BG samples were examined. The findings show that the templating method had no effect on the formation of the required functional elements, such as Si, Ca, Na and P. The porosity of the BG materials improves by 15% after templating compared to the neat sample. The formed pores were assumed to be homogenous based on the uniform adsorption and desorption BET profiles. The crystallization mechanisms during the sintering process were affected by the templating approach, indicating the need for a specific amount of template to be used in the preparation step. Both the sintering temperatures and the CNF content affected the formation of the combeite phase. The BG samples had excellent mechanical properties and are suitable for use in cancellous bone applications. As a result, this study shows a novel method for synthesizing porous bioactive glass materials via the sol-gel method and a CNF suspension as a template.

Polymer-Assisted Metallization of Mammalian Cells.

Developing biotemplating techniques to translate microorganisms and cultured mammalian cells into metallic biocomposites is of great interest for biosensors, electronics, and energy. The metallization of viruses and microbial cells is successfully demonstrated via a genetic engineering strategy or electroless deposition. However, it is difficult to transform mammalian cells into metallic biocomposites because of the complicated genes and the delicate morphological features. Herein, "polymer-assisted cell metallization" (PACM) is reported as a general method for the transformation of mammalian cells into metallic biocomposites. PACM includes a first step of in situ polymerization of functional polymer on the surface and in the interior of the mammalian cells, and a subsequent electroless deposition of metal to convert the polymer-functionalized cells into metallic biocomposites, which retain the micro- and nanostructures of the mammalian cells. This new biotemplating method is compatible with different cell types and metals to yield a wide variety of metallic biocomposites with controlled structures and properties.

Olive Leaves as Biotemplates for Enhanced Solar-Light Harvesting by a Titania-Based Solid.

Olive leaves (by-product from olive oil production in olive mills) were used as biotemplates to synthesize a titania-based artificial olive leaf (AOL). Scanning electron microscopy (SEM) images of AOL showed the successful replication of trichomes and internal structure channels present in olive leaves. The BET surface area of AOL was 52 m2·g-1. X-ray diffraction (XRD) and Raman spectra revealed that the resulting solid was in the predominantly-anatase crystalline form (7.5 nm average particle size). Moreover, the synthesis led to a red-shift in light absorption as compared to reference anatase (gap energies of 2.98 and 3.2 eV, respectively). The presence of surface defects (as evidenced by X-ray photoelectron spectroscopy, XPS, and electron paramagnetic resonance spectroscopy, EPR) and doping elements (e.g., 1% nitrogen, observed by elemental analysis and XPS) could account for that. AOL was preliminarily tested as a catalyst for hydrogen production through glycerol photoreforming and exhibited an activity 64% higher than reference material Evonik P25 under solar irradiation and 144% greater under ultraviolet radiation, (under voltage) UV.

Nanocrystalline cellulose as a biotemplate for preparation of porous titania thin film as a sorbent for thin film microextraction of ketorolac, meloxicam, diclofenac and mefenamic acid.

The present study included the procedure of preparing porous titania thin film using a direct nanocrystalline cellulose templating (NCC) as a bio-template. The microextraction applicability of the porous film was investigated by thin film microextraction (TFME) of the nonsteroidal anti-inflammatory drugs (NSAIDs) including ketorolac, meloxicam, diclofenac and mefenamic acid from different types of urine sample. The extracted NSAIDs were analyzed by HPLC-UV. Under optimum conditions, the calibration curves were linear within the range of 1.0-500 µg L-1 (2.0-200 µg L-1 for ketorolac, 2.0-500 µg L-1 for meloxicam, 1.0-200 µg L-1 for diclofenac and 1.0-200 µg L-1 for mefenamic acid). The limit of detection was found to be between 0.2 and 0.5 µg L-1. The calculated intra- and inter-day relative standard deviations RSDs% (n = 3) at concentration level of 10 µg L-1 were less than 6.3% and 6.0%, respectively. Finally, the method was successfully applied to determine selected NSAIDs in urine samples from different human individuals.

Hybrid Ni@ZnO@ZnS-Microalgae for Circular Economy: A Smart Route to the Efficient Integration of Solar Photocatalytic Water Decontamination and Bioethanol Production.

Water remediation and development of carbon-neutral fuels are a priority for the evermore industrialized society. The answer to these challenges should be simple, sustainable, and inexpensive. Thus, biomimetic-inspired circular and holistic processes combing water remediation and biofuel production can be an appealing concept to deal with these global issues. A simple circular approach using helical Spirulina platensis microalgae as biotemplates to synthesize Ni@ZnO@ZnS photocatalysts for efficient solar water decontamination and bioethanol production during the recycling process is presented. Under solar irradiation, the Ni@ZnO@ZnS-Spirulina photocatalyst exhibits enhanced activity (mineralization efficiency >99%) with minimal photocorrosion and excellent reusability. At the end of its effective lifetime for water remediation, the microalgae skeleton (mainly glycogen and glucose) of the photocatalyst is recycled to directly produce bioethanol by simultaneous saccharification and fermentation process. An outstanding ethanol yield of 0.4 L kg-1, which is similar to the highest yield obtained from oxygenic photosynthetic microorganisms, is obtained. Thus, the entire process allows effective solar photocatalytic water remediation and bioethanol production at room temperature using simple and easily scalable procedures that simultaneously fixes carbon dioxide, thereby constituting a zero-carbon-emission circular process.

A Biotemplating Route for the Synthesis of Hierarchical Fe2 O3 with Highly Dispersed Carbon as Electron-Transfer Channel.

Although the preparation of carbon composites has made great progress, the construction of systems comprising uniformly dispersed carbon as a framework to link active constituents still remains a challenge. Herein, a hierarchical Fe2 O3 /C composite was synthesized in a one-step biotemplating route, where agarose was firstly reacted with Fe3+ and Ca2+ ions, which resulted in a competitive interaction between these ions and the hydroxy groups, then partly calcined to achieve the final product that consisted of α-Fe2 O3 nanoparticles embedded in highly dispersed carbon. The carbon within the composite acts as an efficient photoelectron transfer channel to improve conductivity during photocatalysis. The hierarchical Fe2 O3 /C composite exhibited a photodegradation rate constant (k) of 0.091 min-1 , more than four times that of α-Fe2 O3 (0.020 min-1 ).

Cellulose Nanocrystal-Templated Tin Dioxide Thin Films for Gas Sensing.

Porous tin dioxide is an important low-cost semiconductor applied in electronics, gas sensors, and biosensors. Here, we present a versatile template-assisted synthesis of nanostructured tin dioxide thin films using cellulose nanocrystals (CNCs). We demonstrate that the structural features of CNC-templated tin dioxide films strongly depend on the precursor composition. The precursor properties were studied by using low-temperature nuclear magnetic resonance spectroscopy of tin tetrachloride in solution. We demonstrate that it is possible to optimize the precursor conditions to obtain homogeneous precursor mixtures and therefore highly porous thin films with pore dimensions in the range of 10-20 nm (ABET = 46-64 m2 g-1, measured on powder). Finally, by exploiting the high surface area of the material, we developed a resistive gas sensor based on CNC-templated tin dioxide. The sensor shows high sensitivity to carbon monoxide (CO) in ppm concentrations and low cross-sensitivity to humidity. Most importantly, the sensing kinetics are remarkably fast; both the response to the analyte gas and the signal decay after gas exposure occur within a few seconds, faster than in standard SnO2-based CO sensors. This is attributed to the high gas accessibility of the very thin porous film.

Bioinspired Fe3C@C as Highly Efficient Electrocatalyst for Nitrogen Reduction Reaction under Ambient Conditions.

Developing highly efficient non-precious-metal catalysts for electrochemical reduction reaction is vital for artificial nitrogen fixation under ambient conditions. Herein, we report a bioinspired Fe3C@C composite as an efficient electrocatalyst for nitrogen reduction. The composite based on a leaf skeleton successfully replicates the natural vein structure with multichannels. The Fe3C@C core-shell structure as the real active center contributes to selective electrocatalytic synthesis of ammonia from nitrogen with Faraday efficiency of 9.15% and production rate of 8.53 µg/(h mgcat) or 12.80 µg/(h cm2) at a low potential of -0.2 V versus reversible hydrogen electrode (vs RHE), which is better than that of recently reported carbon- and iron-based materials, even comparable with that of noble-metal-based catalyst. Experiments with density functional theory calculations reveal that graphene-encapsulated Fe3C nanoparticles can improve charge transfer due to core-shell interaction, beneficial for inducing active sites for N2 adsorption and activation and thereby facilitate ammonia synthesis.

Virus-Templated Nickel Phosphide Nanofoams as Additive-Free, Thin-Film Li-Ion Microbattery Anodes.

Transition metal phosphides are a new class of materials generating interest as alternative negative electrodes in lithium-ion batteries. However, metal phosphide syntheses remain underdeveloped in terms of simultaneous control over phase composition and 3D nanostructure. Herein, M13 bacteriophage is employed as a biological scaffold to develop 3D nickel phosphide nanofoams with control over a range of phase compositions and structural elements. Virus-templated Ni5 P4 nanofoams are then integrated as thin-film negative electrodes in lithium-ion microbatteries, demonstrating a discharge capacity of 677 mAh g-1 (677 mAh cm-3 ) and an 80% capacity retention over more than 100 cycles. This strong electrochemical performance is attributed to the virus-templated, nanostructured morphology, which remains electronically conductive throughout cycling, thereby sidestepping the need for conductive additives. When accounting for the mass of additional binder materials, virus-templated Ni5 P4 nanofoams demonstrate the highest practical capacity reported thus far for Ni5 P4 electrodes. Looking forward, this synthesis method is generalizable and can enable precise control over the 3D nanostructure and phase composition in other metal phosphides, such as cobalt and copper.

From Single Molecules to Thin Film Electronics, Nanofibers, e-Textiles and Power Cables: Bridging Length Scales with Organic Semiconductors.

Organic semiconductors are the centerpiece of several vibrant research fields from single-molecule to organic electronics, and they are finding increasing use in bioelectronics and even classical polymer technology. The versatile chemistry and broad range of electronic functionalities of conjugated materials enable the bridging of length scales 15 orders of magnitude apart, ranging from a single nanometer (10-9 m) to the size of continents (106 m). This work provides a taste of the diverse applications that can be realized with organic semiconductors. The reader will embark on a journey from single molecular junctions to thin film organic electronics, supramolecular assemblies, biomaterials such as amyloid fibrils and nanofibrillated cellulose, conducting fibers and yarns for e-textiles, and finally to power cables that shuffle power across thousands of kilometers.