Shape control of single crystalline bismuth nanostructures

Colloidal synthesis of two-dimensional nanocrystals by the polyol route

The field of 2D nanomaterials is ever-growing with a myriad of synthetic advancements that have been used to obtain such materials. There are top-down, as well as bottom-up, fabrication methods for obtaining 2D nanomaterials; however, synthesis of 2D nanomaterials from solution offers a simple scalable way to control size, shape, and surface. This review outlines the recent advances in colloidal polyol synthesis of 2D nanomaterials and provides perspectives on the similarities and differences in various syntheses. Various materials classes are presented and discussed, including metals, oxides, chalcogenides, and halides, that can be synthesized as 2D nanomaterials via a polyol process. Throughout the literature, polyol media is demonstrated to be versatile not only as a solvent and reducing agent for metal precursors but also as a binding and shape-directing agent for many 2D nanomaterials. Polyols also offer the ability to dissolve various surfactants and additives that can further control the morphology and composition of various nanomaterials. In this review, we outline the various 2D materials that have been realized via the solution polyol route.

Bio-fabricated bismuth-based materials for removal of emerging environmental contaminants from wastewater

Although rapid industrialization has made life easier for humans, several associated issues are emerging and harming the environment. Wastewater is regarded as one of the key problems of the 21st century due to its massive production every year and requires immediate attention from all stakeholders to protect the environment. Since the introduction of nanotechnology, bismuth-based nanomaterials have been used in variety of applications. Various techniques, such as hydrothermal, solvo-thermal and biosynthesis, have been reported for synthesizing these materials, etc. Among these, biosynthesis is eco-friendly, cost-effective, and less toxic than conventional chemical methods. The prime focuses of this review are to elaborate biosynthesis of bismuth-based nanomaterials via bio-synthetic agents such as plant, bacteria and fungi and their application in wastewater treatment as anti-pathogen/photocatalyst for pollutant degradation. Besides this, future perspectives have been presented for the upcoming research in this field, along with concluding remarks.

Chemistry of two-dimensional pnictogens: emerging post-graphene materials for advanced applications

The layered allotropes of group 15 (P, As, Sb and Bi), also called two-dimensional (2D) pnictogens, have emerged as one of the most promising families of post-graphene 2D-materials. This is mainly due to the great variety of properties they exhibit, including layer-dependent bandgap, high charge-carrier mobility and current on/off ratios, strong spin-orbit coupling, wide allotropic diversity and pronounced chemical reactivity. These are key ingredients for exciting applications in (opto)electronics, heterogeneous catalysis, nanomedicine or energy storage and conversion, to name a few. However, there are still many challenges to overcome in order to fully understand their properties and bring them to real applications. As a matter of fact, due to their strong interlayer interactions, the mechanical exfoliation (top-down) of heavy pnictogens (Sb & Bi) is unsatisfactory, requiring the development of new methodologies for the isolation of single layers and the scalable production of high-quality flakes. Moreover, due to their pronounced chemical reactivity, it is necessary to develop passivation strategies, thus preventing environmental degradation, as in the case of bP, or controlling surface oxidation, with the corresponding modification of the interfacial and electronic properties. In this Feature Article we will discuss, among others, the most important contributions carried out in our group, including new liquid phase exfoliation (LPE) processes, bottom-up colloidal approaches, the preparation of intercalation compounds, innovative non-covalent and covalent functionalization protocols or novel concepts for potential applications in catalysis, electronics, photonics, biomedicine or energy storage and conversion. The past years have seen the birth of the chemistry of pnictogens at the nanoscale, and this review intends to highlight the importance of the chemical approach in the successful development of routes to synthesise, passivate, modify, or process these materials, paving the way for their use in applications of great societal impact.

Plate-Like Colloidal Metal Nanoparticles

The pseudo-two-dimensional (2D) morphology of plate-like metal nanoparticles makes them one of the most anisotropic, mechanistically understood, and tunable structures available. Although well-known for their superior plasmonic properties, recent progress in the 2D growth of various other materials has led to an increasingly diverse family of plate-like metal nanoparticles, giving rise to numerous appealing properties and applications. In this review, we summarize recent progress on the solution-phase growth of colloidal plate-like metal nanoparticles, including plasmonic and other metals, with an emphasis on mechanistic insights for different synthetic strategies, the crystallographic habits of different metals, and the use of nanoplates as scaffolds for the synthesis of other derivative structures. We additionally highlight representative self-assembly techniques and provide a brief overview on the attractive properties and unique versatility benefiting from the 2D morphology. Finally, we share our opinions on the existing challenges and future perspectives for plate-like metal nanomaterials.

A review on bismuth-based nanocomposites for energy and environmental applications

Bismuth, a heavy metal which is found to be inexpensive and at a reduced cost, is utilized in the synthesis of different nanomaterials with novel structure, remarkable physical and chemical properties, adjustable bandgap, notable efficiency for photothermal conversion. These characteristics have made this element desirable for various applications such as storage and conversion of energy, electronics, sensors, photocatalysis, and other biomedical applications. These review papers are the vital points for the students, this report guides them to the research papers which focus on the impressive development in the area of bismuth and similar nanostructures. The purpose of the present review is to discuss the various synthesis routes of bismuth-based nanomaterials along with green synthesis, different nanostructures of bismuth, their significant properties, diverse applications and directions for the upcoming research. Therefore, with these different tuneable synthesis methods of bismuth-based nanomaterials combined with their novel properties, would elucidate on the future devices based on various nanostructures of bismuth.

Fabrication of Fe/Bi bimetallic magnetic nano-oxides (IBBMNOs) as efficient remediator for hexavalent chromium from aqueous environment

In this study, highly efficient Fe/Bi bimetallic magnetic nanooxides (IBBMNOs) were used as adsorbent for the removal of Cr(VI) from an aqueous environment. The IBBMNOs were synthesized by a simple and facile chemical reduction method. After that, different analytical techniques were used to characterize the resultant nanomaterial. According to characterization results, the IBBMNOs are highly porous look like cotton beads with an average size of 60-69 nm. BET results show that IBBMNOs are highly porous with a high surface area. After optimizing different parameters such as pH, adsorbent dose, and time study, an excellent adsorption capacity was achieved up to 185 mg/g in 10 min. The calculated data of the adsorption process was well fitted with Langmuir and pseudo-first-order kinetic model. The prepared materials have good usability as compared to reported adsorbent materials can be used for five different cycles with good removal efficiency of chromium ion from aqueous samples. Schematic illustration of adsorption of Cr(VI) from aqueous solution by IBBMNOs.

Promoting the Electrocatalytic Reduction of CO2 on Ultrathin Porous Bismuth Nanosheets with Tunable Surface-Active Sites and Local pH Environments

Electrochemical CO₂ reduction reaction (CO₂RR) yielding value-added chemicals provides a sustainable approach for renewable energy storage and conversion. Bismuth-based catalysts prove to be promising candidates for converting CO₂ and water into formate but still suffer from poor selectivity and activity and/or sluggish kinetics. Here, we report that ultrathin porous Bi nanosheets (Bi-PNS) can be prepared through a controlled solvothermal protocol. Compared with smooth Bi nanoparticles (Bi-NPs), the ultrathin, rough, and porous Bi-PNS provide more active sites with higher intrinsic reactivities for CO₂RR. Moreover, such high activity further increases the local pH in the vicinity of the catalyst surfaces during electrolysis and thus suppresses the competing hydrogen evolution reaction. As a result, the Bi-PNS exhibit significantly boosted CO₂RR properties, showing a Faradaic efficiency of 95% with an effective current density of 45 mA cm^-2 for formate evolution at the potential of -1.0 V versus reversible hydrogen electrode.

Inducing thermodynamically blocked atomic ordering via strongly driven nonequilibrium kinetics

Ultrafast light-matter interactions enable inducing exotic material phases by promoting access to kinetic processes blocked in equilibrium. Despite potential opportunities, actively using nonequilibrium kinetics for material discovery is limited by the poor understanding on intermediate states of driven systems. Here, using single-pulse time-resolved imaging with x-ray free-electron lasers, we found intermediate states of photoexcited bismuth nanoparticles that showed kinetically reversed surface ordering during ultrafast melting. This entropy-lowering reaction was further investigated by molecular dynamics simulations to reveal that observed kinetics were thermodynamically buried in equilibrium, which emphasized the critical role of electron-mediated ultrafast free-energy modification in inducing exotic material phases. This study demonstrated that ultrafast photoexcitations of electrons provide an efficient strategy to induce hidden material phases by overcoming thermodynamic barriers via nonequilibrium reaction pathways.

Colloidal chemical bottom-up synthesis routes of pnictogen (As, Sb, Bi) nanostructures with tailored properties and applications: a summary of the state of the art and main insights

Adjusting the colloidal chemistry synthetic parameters for pnictogen nanostructures leads to a fine control of their physical properties and the resulting performance in applications. Image adapted from Slidesgo.com.

Development of Proportional-Integrative-Derivative (PID) Optimized for the MicroElectric Discharge Machine Fabrication of Nano-Bismuth Colloid

Metal nanoparticles are typically prepared by using a chemical method, and a suspension is added to control the particle size and concentration of the nanoparticles. In this study, a micro-electric discharge machine (micro-EDM) was used to melt bismuth into nanoparticles, thus yielding a colloidal solution. No chemicals were added during the manufacturing process, and pure water was used as the medium. The colloid was assessed using an electrohydraulic system, and process parameters were adjusted for optimization; additionally, the discharge pulse wave was analyzed. The proposed preparation process is simple, fast, and cost-effective; moreover, the manufacturing process allows for mass production and reduces environmental pollution. Experimental results revealed that the nano-bismuth (nano-bi) colloidal solution was successfully prepared by the micro-EDM, and absorption peaks in the UV-vis spectrum were observed at 234 and 237 nm. Moreover, to optimize the proportional-integral-derivative (PID) control parameters to be used in the micro-EDM to prepare the nano-bi colloidal solution, this study derived a mathematical model of the micro-EDM. MATLAB was used to obtain the PID parameters. The discharge success rate (74.1876%) for the nano-bi colloidal solution prepared using our method was higher than that (46.9196%) obtained for a nano-bi colloidal solution prepared using an online adaptation method.

Fe(II)-Assisted one-pot synthesis of ultra-small core-shell Au-Pt nanoparticles as superior catalysts towards the HER and ORR

In this work, uniform ultra-small core-shell Au-Pt nanoparticles (denoted as USCS Au-Pt NPs) with Au-decorated Pt surfaces are successfully prepared by Fe(ii)-assisted one-pot co-reduction of Au(iii) ions and Pt(ii) ions in a citrate solution. The as-prepared USCS Au38.4@Au9.3Pt52.3 NPs have an average diameter of 2.3 ± 0.5 nm. It is found that the morphology, composition and size of Au-Pt NPs are highly dependent on the reaction conditions including the addition sequence of the precursors, and the concentrations of Fe(ii) ions, Au(iii) ions and Pt(ii) ions. In addition, USCS Au38.4@Au9.3Pt52.3-NP/C catalysts (USCS Au38.4@Au9.3Pt52.3 NPs loaded on the Vulcan XC-72R carbon black) exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR) in acidic media due to the higher electrochemically active surface area (ECSA) and electronic effect between Pt and Au. For instance, USCS Au38.4@Au9.3Pt52.3-NP/C catalysts exhibited greatly enhanced HER activity in terms of overpotential (16 mV at a current density of -10 mA cm-2) and are better than commercial Pt/C catalysts (31 mV at a current density of -10 mA cm-2) reported in the literature thus far, to the best of our knowledge. Strikingly, their mass activity is about 13.1-fold higher than that of commercial Pt/C catalysts. Moreover, they also show an improved ORR activity, Eonset = 1.015 V and E1/2 = 0.896 V, which are positively shifted by nearly 28 mV and 21 mV than those of commercial Pt/C catalysts (0.987 V and 0.875 V), respectively. In addition, they also showed a higher kinetic current density (12.85 mA cm-2 at 0.85 V) and a better long-term durability. Our synthetic strategy presented here may be extended to the preparation of ultra-small Au-based bimetallic or multi-metallic NPs.

Synthesis of SiC/BiOCl Composites and Its Efficient Photocatalytic Activity

BiOCl nanosheets nucleated and grew on cottage cheese-like SiC substrate via hydrothermal procedure, through which a tight heterojunction was formed. SiC/BiOCl composites with varied morphologies were acquired that the formation of BiOCl was involved with different form of carbon existed on surface of SiC. The photocatalytic mechanism analysis revealed that the combination of SiC and BOC significantly enhanced photocatalytic activities owing to the improved visible light utilization, efficient separation of photo-generated carriers, and promoted reactive area. The main active species during the photocatalytic reaction was determined as ·O2− radical by additionally adding trapping agent into the reactant. The SiC-BOC composites showed much higher photoactivities in photocurrent responses and photocatalytic degradation of TC-HCl, which mainly attributed to the well-built heterointerface promoted by Bi-C bonds and the interlaced structure obtained by increasing exposure of (010) facets in BiOCl. The nucleation, growth and combination architecture of BiOCl was all influenced by the involvement of SiC.

The versatile biomedical applications of bismuth-based nanoparticles and composites: therapeutic, diagnostic, biosensing, and regenerative properties

Studies of nanosized forms of bismuth (Bi)-containing materials have recently expanded from optical, chemical, electronic, and engineering fields towards biomedicine, as a result of their safety, cost-effective fabrication processes, large surface area, high stability, and high versatility in terms of shape, size, and porosity. Bi, as a nontoxic and inexpensive diamagnetic heavy metal, has been used for the fabrication of various nanoparticles (NPs) with unique structural, physicochemical, and compositional features to combine various properties, such as a favourably high X-ray attenuation coefficient and near-infrared (NIR) absorbance, excellent light-to-heat conversion efficiency, and a long circulation half-life. These features have rendered bismuth-containing nanoparticles (BiNPs) with desirable performance for combined cancer therapy, photothermal and radiation therapy (RT), multimodal imaging, theranostics, drug delivery, biosensing, and tissue engineering. Bismuth oxyhalides (BiO_x, where X is Cl, Br or I) and bismuth chalcogenides, including bismuth oxide, bismuth sulfide, bismuth selenide, and bismuth telluride, have been heavily investigated for therapeutic purposes. The pharmacokinetics of these BiNPs can be easily improved via the facile modification of their surfaces with biocompatible polymers and proteins, resulting in enhanced colloidal stability, extended blood circulation, and reduced toxicity. Desirable antibacterial effects, bone regeneration potential, and tumor growth suppression under NIR laser radiation are the main biomedical research areas involving BiNPs that have opened up a new paradigm for their future clinical translation. This review emphasizes the synthesis and state-of-the-art progress related to the biomedical applications of BiNPs with different structures, sizes, and compositions. Furthermore, a comprehensive discussion focusing on challenges and future opportunities is presented.

Synthesis and formation mechanism of self-assembled 3D flower-like Bi/γ-Fe2O3 composite particles

The self-assembled 3D flower-like Bi/γ-Fe₂O₃ composite particles consist of a Bi nanosphere core and a γ-Fe₂O₃ nanopetal shell.

The polyol process: a unique method for easy access to metal nanoparticles with tailored sizes, shapes and compositions

After about three decades of development, the polyol process is now widely recognized and practised as a unique soft chemical method for the preparation of a large variety of nanoparticles which can be used in important technological fields. It offers many advantages: low cost, ease of use and, very importantly, already proven scalability for industrial applications. Among the different classes of inorganic nanoparticles which can be prepared in liquid polyols, metals were the first reported. This review aims to give a comprehensive account of the strategies used to prepare monometallic nanoparticles and multimetallic materials with tailored size and shape. As regards monometallic materials, while the preparation of noble as well as ferromagnetic metals is now clearly established, the scope of the polyol process has been extended to the preparation of more electropositive metals, such as post-transition metals and semi-metals. The potential of this method is also clearly displayed for the preparation of alloys, intermetallics and core-shell nanostructures with a very large diversity of compositions and architectures.

Nanobismuth: Fabrication, Optical, and Plasmonic Properties—Emerging Applications

Along the twentieth century, the electronic properties of bismuth have been widely studied, especially in relation with its magnetoresistive and thermoelectric responses. In this context, a particular emphasis has been made on electronic confinement effects in bismuth nanostructures (or nanobismuth). In the recent years, the optical properties of bismuth nanostructures are focusing a growing interest. An increasing number of reports point at the potential of such nanostructures to support plentiful optical resonances over an ultrabroad spectral range: “interband plasmonic” resonances in the ultraviolet, visible, and near-infrared; dielectric Mie resonances in mid- and far-infrared; and conventional free-carrier plasmonic resonances in the far-infrared and terahertz. With the aim to provide a comprehensive basis for exploiting the full optical potential of bismuth nanostructures, we review the current progress in their controlled fabrication, the trends reported (from theoretical calculations and experimental observations) for their optical and plasmonic response, and their emerging applications, including photocatalysis and switchable metamaterials.

Facile Synthesis of Uniform-Sized Bismuth Nanoparticles for CT Visualization of Gastrointestinal Tract in Vivo

High-performance and biocompatible contrast agents are the key to accurate diagnosis of various diseases in vivo via CT imaging. Fabrication of pure Bi nanoparticles is the best way to maximize X-ray absorption efficiency due to the ultrahigh X-ray attenuation ability of Bi and 100% content of Bi element. However, high-quality Bi nanoparticles prepared through a facile strategy are still lacking. Herein, we report a simple noninjection method to fabricate uniformly sized pure Bi nanoparticles using only two commercial reagents by simply heating the mixture of raw materials in a short time. The obtained Bi nanoparticles owned highly uniform size, excellent monodispersity, and impressive antioxidant capacity. After being modified with oligosaccharide, the "sweet" Bi nanoprobe with comfortable patient experience and favorable biocompatibility was successfully used in CT visualization of gastrointestinal tract in detail.

Shape-controlled synthesis of three-dimensional triangular bismuth microstructures and sensing of H2O2

The electrodeposition of triangular microstructures of Bi on indium tin oxide surfaces is carried out by optimizing the potentials, precursor concentrations and deposition times.

One-pot preparation of Bi/Bi2WO6/reduced graphene oxide as a plasmonic photocatalyst with improved activity under visible light

The Bi/Bi₂WO₆/rGO nanocomposite for simultaneous RhB adsorption and photocatalysis was synthesized by a one-pot hydrothermal method.

Bismuth nanoparticles integration into heavy metal electrochemical stripping sensor

Between their many applications bismuth nanoparticles (BiNPs) are showing interest as pre-concentrators in heavy metals detection while being applied as working electrode modifiers used in electrochemical stripping analysis. From the different reported methods to synthesize BiNPs we are focused on the typical polyol method, largely used in these types of metallic and semi-metallic nanoparticles. This study presents the strategy for an easy control of the shape and size of BiNPs including nanocubes, nanosferes and triangular nanostructures. To improve the BiNP size and shape, different reducing agents (ethylene glycol or sodium hypophosphite) and stabilizers (polyvinyl pyrrolidone, PVP, in different amounts) have been studied. The efficiency of BiNPs for heavy metals analysis in terms of detection sensitivity while being used as modifiers of screen-printed carbon electrodes including the applicability of the developed device in real sea water samples is shown. A parallel study between the obtained nanoparticles and their performance in heavy metal sensing has been described in this communication.

Synthesis of micro sphere-like bismuth nanoparticles by microwave assisted polyol method; designing a novel electrochemical nanosensor for ultra-trace measurement of Pb2+ ions

Bi nanostructures were synthesized in the presence of propylene glycol as the solvent and surfactant through microwave method.

BiAg alloy nanospheres: a new photocatalyst for H2 evolution from water splitting

We demonstrate for the first time that Bi and BiAg alloy nanospheres, fabricated with a facile hydrothermal method, display evident photocatalytic H2 production activities. Element Bi can serve as an active photocatalyst for both water splitting and photoelectrochemical applications. More interestingly, these activities of Bi can be greatly enhanced by introducing Ag to form BiAg alloy nanoparticles, which may be ascribed to the improved charge separation and enlarged carrier concentration. The constituent of the BiAg alloy can be rationally tuned by varying the amount of Ag nanowires, and it is found that Bi0.7Ag0.3 exhibits the highest photoelectrochemical property.

Synthesis of Bi nanowire networks and their superior photocatalytic activity for Cr(vi) reduction

Interconnected Bi nanowire networks were synthesized for the first time via a solvothermal route by using ethylene glycol (EG) as both a solvent and a reducing agent, and citric acid (CA) as a stabilizing agent at a molar ratio of CA/Bi(3+) = 5. Among various reaction conditions including the temperature, reaction time and precursor concentration, the molar ratio of CA/Bi(3+) was the dominant experimental parameter to influence the morphology and structures of the Bi crystals. Highly dispersed Bi microspheres and network-like Bi thick wires were obtained if the molar ratio of CA/Bi(3+) was changed to 2.5 and 10, respectively. As compared to other additives including trisodium citrate, cetyltrimethylammonium bromide (CTAB) and oxalic acid, good solubility of CA in EG together with its coordination effect played a crucial role in the formation of network-like Bi nanowires. The Bi nanowire networks exhibited excellent photocatalytic performance for Cr(vi) reduction. Cr(vi) was completely reduced to less toxic Cr(iii) after 8 min and 55 min of UV and visible-light irradiation, respectively.

Synthesis, X-ray Opacity, and Biological Compatibility of Ultra-High Payload Elemental Bismuth Nanoparticle X-ray Contrast Agents

Inorganic nanoscale X-ray contrast agents (XCAs) offer many potential advantages over currently used intravascular molecular contrast agents, including longer circulation and retention times, lower administration volumes, and greater potential for site directed imaging. Elemental bismuth nanoparticles (BiNPs) are particularly attractive candidate XCAs due to the low cost, the high atomic number and high density of bismuth, and the likelihood that BiNPs will oxidatively decompose to biocompatible bismuth(III) ions at controlled rates for renal excretion. Herein we describe the synthesis of ultrahigh payload BiNPs in 1,2-propanediol using a borane reducing agent and glucose as a biocompatible surface stabilizer. Both synthetic solvent (1,2-propanediol) and surfactant (glucose) are evident on the BiNP surfaces when analyzed by ¹H NMR and FT-IR spectroscopies. These particles contain ∼6 million Bi atoms per NP and have large inorganic cores (74 nm by TEM) compared to their hydrodynamic size (86 nm by DLS). Thus, the dense BiNP core constitutes the majority (∼60%) of each particle's volume, a necessary property to realize the full potential of nanoscale XCAs. Using quantitative computed tomography in phantom and in vitro imaging studies, we demonstrate that these BiNPs have greater X-ray opacity than clinical small molecule iodinated contrast agents at the same concentrations. We furthermore demonstrate a favorable biocompatibility profile for these BiNPs in vitro. Altogether, these studies indicate that these ultrahigh payload BiNPs, synthesized from known biocompatible components, have promising physical and cytotoxicological properties for use as XCAs.

Nano- and micro-hexagons of bismuth on polycrystalline copper: electrodeposition and heavy metal sensing

Tuning the electroreduction of NO₃⁻vis-à-vis Bi³⁺ results in nano-/micro-hexagons. Nanohexagons are highly sensitive to trace detection of lead.

Sonoelectrochemical synthesis and assembly of bismuth-antimony alloy: from nanocrystals to nanoflakes

Bismuth-based nanostructures have attracted growing interest because of their promising thermoelectric properties and applications in optics and electronics. Pulsed sonoelectrochemical technique was selected to fabricate bismuth-antimony (BiSb) flake-like alloy in ethylene glycol aqueous solution. The formation mechanism for the BiSb alloy was discussed. Ultrasonic played an important role in regenerating electrode and promoting the formation of BiSb nanoflakes. Citrate and polyvinylpyrrolidone (PVP) were introduced as mixed controlling agents during the nucleation and growth process.

Bismuth hexagons: facile mass synthesis, stability and applications

A unique direct electrodeposition technique involving very high current densities, high voltages and high electrolyte concentrations is applied for highly selective mass synthesis of stable, isolable, surfactant-free, single-crystalline Bi hexagons on a Cu wire at room temperature. A formation mechanism of the hexagons is proposed. The morphology, phase purity, and crystallinity of the material are well characterized by FESEM, AFM, TEM, SAED, EDX, XRD, and Raman spectroscopy. The thermal stability of the material under intense electron beam and intense laser light irradiation is studied. The chemical stability of elemental Bi in nitric acid shows different dissolution rates for different morphologies. This effect enables a second way for the selective fabrication of Bi hexagons. Bi hexagons can be oxidized exclusively to α-Bi(2)O(3) hexagons. The Bi hexagons are found to be promising for thermoelectric applications. They are also catalytically active, inducing the reduction of 4-nitrophenol to 4-aminophenol. This electrodeposition methodology has also been demonstrated to be applicable for synthesis of bismuth-based bimetallic hybrid composites for advanced applications.

Solvothermal synthesis of uniform bismuth nanospheres using poly(N-vinyl-2-pyrrolidone) as a reducing agent

Uniform bismuth nanospheres were successfully prepared from bismuth nitrate in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) by solvothermal process. The product was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray. PVP plays a critical role both as a reducing agent and a capping agent in the formation of bismuth nanospheres. Shape and size of bismuth nanospheres could be tuned by changing the employed PVP/bismuth salt ratio. It was also found the solvent had an effect on the morphologies of bismuth nanomaterials. The possible formation and growth mechanism of bismuth nanospheres were also discussed and proposed to explain the reduction step.

Preparation of nanoscale PbSe particles with different morphologies in diethylene glycol

Nanoscale PbSe particles with different morphologies including octahedral, tetradecahedral and cubic shapes have been successfully prepared in diethylene glycol (DEG) at 240 degrees C in the presence of PVP-K30: poly(vinyl pyrrolidone), M(W) = 50 000. The formation of PbSe is believed to be an elemental recombination process of corresponding elements reduced from their precursors by the solvent. Experimental results showed that a prominent morphological variation was observed through varying the molar ratios of selenius acid to Pb(2+) when Pb(Ac)(2) was used as lead precursor, while the sizes of the final PbSe products tended to increase along with the increase of the molar ratios of selenius acid to Pb(2+) when Pb(NO(3))(2) was used as lead precursor.

Shape-controlled synthesis of metal nanocrystals: simple chemistry meets complex physics?

Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Large-scale polyol synthesis of single-crystal bismuth nanowires and the role of NaOH in the synthesis process

A modified polyol process is introduced for the production of single-crystal bismuth (Bi) nanowires with uniform diameters along each wire in relatively high yield. The appropriate amount of NaOH in the solution reacts with Bi(3+) to form water-soluble complexing ions BiO(2)(-). The tiny Bi nanoparticles formed at the initial stage could serve as seeds for the subsequent growth of Bi nanostructures in the refluxing process with the aid of PVP. We find that the amount of NaOH determines the reduction rate of BiO(2)(-), which influences the morphologies of the synthesized Bi nanostructures. High reduction rates result in nanowires and nanoparticles, while low reduction rates result in nanoplates.

Titania encapsulation of flat gold nanoparticles — A simple route to Au@TiO2 core-shell nanosheets

We report the attachment of a uniform coating of a thin layer of amorphous TiO2 to flat gold nanoparticles via a simple sol–gel process. Coatings of variable thickness ranging from 5 to 100 nm have been produced. Activation of the Au particles was unnecessary. However, the ability to coat the flat gold nanoparticles was dependent on the method used for their synthesis. In addition, the amorphous TiO2 shell was hydrothermally treated to induce crystallization to the anatase polymorph. The desired nanocrystalline anatase morphology was obtained by heating in water at 70 °C for 1 week. A similar result was also obtained when the material was heated to 130 °C for 5 min in a microwave reactor. These new Au@TiO2 nanosheets were characterized by TEM, EDX, and SAED.Key words: core-shell, titanium dioxide, anisotropic nanoparticles, semiconductor thin films, nanocomposite material.