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Herein, we report an aerobic synthesis method to produce bismuth nanoparticles (Bi NPs) with average diameters in the range 40-80 nm using commercially available bismuth triiodide (BiI3) as the starting material; the method uses only readily available chemicals and conventional laboratory equipment. Furthermore, size data from replicates of the synthesis under standard reaction conditions indicate that this method is highly reproducible in achieving Bi NP populations with low standard deviations in the mean diameters. We also investigated the mechanism of the reaction, which we determined results from the reduction of a soluble alkylammonium iodobismuthate precursor species formed in situ. Under appropriate concentration conditions of iodobismuthate anion, we demonstrate that burst nucleation of Bi NPs results from reduction of Bi3+ by the coordinated, redox non-innocent iodide ligands when a threshold temperature is exceeded. Finally, we demonstrate phase transfer and silica coating of the Bi NPs, which results in stable aqueous colloids with retention of size, morphology, and colloidal stability. The resultant, high atomic number, hydrophilic Bi NPs prepared using this synthesis method have potential for application in emerging x-ray contrast and x-ray therapeutic applications.

High-density inorganic nanoparticles have shown promise in medical applications that utilize radiation including X-ray imaging and as radiation dose enhancers for radiotherapy. We have developed an aqueous synthetic method to produce small (~ 2 nm) iridium nanoparticles (IrNPs) by reduction of iridium(III) chloride using a borohydride reducing agent. Unlike other solution-based synthesis methods, uniform and monodispersed IrNPs are produced without the use of surfactants or other solubilizing ligands. These nanoparticles are highly crystalline as observed by X-ray diffraction and high-resolution transmission electron microscopy (TEM). In vitro metabolic toxicity assays using hepatocyte and macrophage cells demonstrate that both IrNPs and iridium(III) chloride are well tolerated at concentrations of up to 10 μM iridium. Furthermore, the IrNPs were assessed in a hemolytic assay and found to have no significant impact on red blood cells when exposed to concentrations up to 100 μM. Overall, these results support the potential for the in vivo application of this nanomaterial. Electronic supplementary material The online version of this article (10.1186/s11671-018-2621-3) contains supplementary material, which is available to authorized users.

Stable, aqueous, red-to-near infrared emission is critical for the use of silicon nanoparticles (Si NPs) in biological fluorescence assays, but such Si NPs have been difficult to attain. We report a synthesis and surface modification strategy that protects Si NPs and preserves red photoluminescence (PL) in water for more than 6 mo. The Si NPs were synthesized via high temperature reaction, liberated from an oxide matrix, and functionalized via hydrosilylation to yield hydrophobic particles. The hydrophobic Si NPs were phase transferred to water using the surfactant cetyltrimethylammonium bromide (CTAB) with retention of red PL. CTAB apparently serves a double role in providing stable, aqueous, red-emitting Si NPs by (i) forming a hydrophobic barrier between the Si NPs and water and (ii) providing aqueous colloidal stability via the polar head group. We demonstrate preservation of the aqueous red emission of these Si NPs in biological media and examine the effects of pH on emission color.

The photophysical properties of silicon semiconductor nanocrystals (SiNCs) are extremely sensitive to the presence of surface chemical defects, many of which are easily produced by oxidation under ambient conditions. The diversity of chemical structures of such defects and the lack of tools capable of probing individual defects continue to impede understanding of the roles of these defects in SiNC photophysics. We use scanning tunneling spectroscopy to study the impact of surface defects on the electronic structures of hydrogen-passivated SiNCs supported on the Au(111) surface. Spatial maps of the local electronic density of states (LDOS) produced by our measurements allowed us to identify locally enhanced defect-induced states as well as quantum-confined states delocalized throughout the SiNC volume. We use theoretical calculations to show that the LDOS spectra associated with the observed defects are attributable to Si-O-Si bridged oxygen or Si-OH surface defects.

In order to improve specific capacitance and limit electrical resistance, high-quality exfoliated graphene decorated with transition metal (Fe, Mn, Co) oxide nanoparticles (NPs) has been successfully synthesized without the use of surfactantvia a simple, general, environmentally-friendly chemical process. The specific capacitance of as-prepared graphene/Mn3O4 composite reach 239.6 F/g, when employed as the anode material in neutral NaCl electrolyte solutions (cf. 98.2 F/g for pristine graphene and 141.4 F/g for pure Mn3O4 NPs), which indicate the synergetic effects from both graphene and attached Mn3O4 NPs. Moreover, the high conductivity of graphene eliminates the need for conductive carbon black as fillers. The current density of graphene/Mn3O4 reached as high as 4.5 A g−1 which is much higher than that of graphene oxide (GO) or reduced GO-based composites. This significant enhancement of capacitance and current density was attributed to the surfactant-free approach to hybridize graphene with transition metal oxide NPs, the excellent conductivity of pristine graphene combined with its large surface area, as well as a uniform distribution of NPs on the clean surface of conductive graphene. Thus the low-toxicity, inexpensive graphene-based hybrids show promising utility as high current density electrode materials for supercapacitor applications.

We have developed a versatile, one-step melt synthesis of water-soluble, highly emissive silicon nanoparticles using bi-functional, low-melting solids (such as glutaric acid) as reaction media. Characterization through transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy shows that the one-step melt synthesis produces nanoscale Si cores surrounded by a silicon oxide shell. Analysis of the nanoparticle surface using FT-IR, zeta potential, and gel electrophoresis indicates that the bi-functional ligand used in the one-step synthesis is grafted onto the nanoparticle, which allows for tuning of the particle surface charge, solubility, and functionality. Photoluminescence spectra of the as-prepared glutaric acid-synthesized silicon nanoparticles show an intense blue-green emission with a short (ns) lifetime suitable for biological imaging. These nanoparticles are found to be stable in biological media and have been used to examine cellular uptake and distribution in live N2a cells.

The inorganic-organic salts (H{sub 2}TMDP){sub 3}(Bi{sub 2}I{sub 9}){sub 2} (1), (H{sub 2}TMDP){sub 2}(Bi{sub 4}I{sub 16}).2EtOH (2), (H{sub 2}TMDP){sub 2}(Bi{sub 6}I{sub 22}).2EtOH (3), and (H{sub 2}TMDP){sub 2}(Bi{sub 6}I{sub 22}) (4) were synthesized and structurally characterized from the solvothermal reaction of 1,3-bis-(4-piperidyl)propane (TMDP) and BiI{sub 3} by adjusting the relative ratio of the reactants. The anions of the compounds consist of 2 (1), 4 (2), or 6 (3 and 4) BiI{sub 6} polyhedra, which are joined by face- (1) or edge-sharing (2-4) to form discrete anions. The size of the discrete anion, in terms of the number of connected polyhedra, is observed to increase as the ratio of BiI{sub 3} to TMDP is increased. A related compound (H{sub 2}TMDP)(Bi{sub 3}I{sub 11}).(H{sub 2}O) (5) was synthesized and structurally characterized using the same two reactants in the presence of HF. The anion of 5 is polymeric rather than discrete, with a trioctahedral repeat unit.

The new metal-organic framework materials, ZnF(Am{sub 2}TAZ).solvents and ZnF(TAZ).solvents (Am{sub 2}TAZ=3,5-diamino-1,2,4-triazole, TAZ=1,2,4-triazole), have been synthesized solvothermally and structurally characterized by either Rietveld refinement from powder XRD data or by single crystal X-ray diffraction. The three-dimensional structures of the compounds display open-ended, tubular channels, which are constituted of covalently bonded hexanuclear metallamacrocycles (Zn{sub 6}F{sub 6}(ligand){sub 6}). The tubular channels are subsequently covalently joined into a honeycomb-like hexagonal array to generate the three-dimensional porous framework. In the case of ZnF(Am{sub 2}TAZ).solvents, hydrophilic -NH{sub 2} groups point into the channels, effectively reducing their inner diameter relative to ZnF(TAZ).solvents. The present compounds are isostructural to one another and to the previously reported ZnF(AmTAZ).solvents (AmTAZ=3-amino-1,2,4-triazole), illustrative of the fact that the internal size and chemical properties of the framework may be altered by modification of the small, heterocyclic ligand. In addition to demonstrating the ability to modify the basic framework, ZnF(TAZ).solvents and ZnF(Am{sub 2}TAZ).solvents are two of the most thermally stable coordination frameworks known to date. - Graphical abstract: Top view of the open-ended, honeycomb tubular architecture of ZnF(Am{sub 2}TAZ)

The polymeric title complex, [Zn(NO3)2(C24H20N8)(H2O)2]n, features distorted ZnN2O4 octa­hedra with each ZnII atom being located on an inversion center. Adjacent Zn ions are doubly bridged by two equivalent 1,4-di-3-pyridyl-2,3-diaza-1,3-butadiene ligands to form linear chains.

The title compound, [Cu(C8H4F3O2S)2(C12H10N4)]n or [Cu(tta)2(L2)2]n (L2 = 1,4-di-3-pyridyl-2,3-diaza-1,3-butadiene and tta = α-thenoyltrifluoro­acetonate), consists of undulating chains containing two crystallographically distinct CuII centers that are each located on inversion centers. Each CuII center exhibits distorted octa­hedral coordination provided by two pyridyl N atoms from two equivalent L2 ligands and four O atoms from two equivalent tta ligands. The chains inter­act through weak C—F⋯H—C contacts.

The new iodo­bismuthate compound (C13H11N2O)4[Bi6I22] has been synthesized solvothermally by reacting BiI3, Zn(NO3)2·6H2O and 4,5-diaza­fluoren-9-one in a water/ethanol solvent mixture. The asymmetric unit of the compound contains two independent [N-ethyl-4,5-dafo]+ cations and one-half of a centrosymmetric [Bi6I22]4− anion. The average terminal Bi—I, Bi—μ2-I and Bi—μ3-I bond lengths in the anion are 2.8923 (2), 3.1403 (2) and 3.3022 (2) A, respectively.

The title bis­muth-iodide compound, [Bi2I6(C12H8N2)2], has been synthesized solvothermally by reacting BiI3, Mn(CH3COO)2·4H2O, and 1,10-phenanthroline in an ethanol/water solvent mixture. The compound contains two bis­muth centers that are each coordinated by a phenanthroline ligand and two terminal iodide ligands, and the bis­muth centers are bridged via two additional iodide ligands to form a mol­ecular dimer. The asymmetric unit of the compound consists of one half of a single dimer mol­ecule located on a crystallographic inversion center.

In the one-dimensional title polymer, [Cu(C8H4F3O2S)2(C12H10N4)]n or [Cu(L)2(tta)2] [tta is α-thenoyl­trifluoro­acetonato and L is 1,4-bis­(4-pyrid­yl)-2,3-diaza-1,3-butadiene], Cu2+ lies on a center of inversion. It is axially coordinated by two pyridyl N atoms from two different L ligands and equatorially coordinated by four O atoms from two chelating tta ligands. The ligand L propagates the one-dimensional chain structure by serving as a bridging ligand between two Cu octa­hedra via Cu—N coordinate bonds.

The asymmetric unit of the title compound, [Co(C2H8N2)3][Bi2I9], crystallizes in the ortho­rhom­bic space group Cmc21. The asymmetric unit contains half of a [Co(en)3]3+ cation (en is ethyl­enediamine) and half of a [Bi2I9]3− anion. Both species are located on mirror planes, requiring the [Co(en)3]3+ cation to be present as a statistically disordered mixture of both enantiomeric forms. Crystals were grown solvothermally from an ethanol–water solvent mixture using rac-[Co(en)3]I3 and bis­muth triiodide as starting materials. The compound is a rare example of a mixed-metal halobismuthate material.

We present results of a scanning tunneling spectroscopy (STS) study of the impact of dehydrogenation on the electronic structures of hydrogen-passivated silicon nanocrystals (SiNCs) supported on the Au(111) surface. Gradual dehydrogenation is achieved by injecting high-energy electrons into individual SiNCs, which results, initially, in reduction of the electronic bandgap, and eventually produces midgap electronic states. We use theoretical calculations to show that the STS spectra of midgap states are consistent with the presence of silicon dangling bonds, which are found in different charge states. Our calculations also suggest that the observed initial reduction of the electronic bandgap is attributable to the SiNC surface reconstruction induced by conversion of surface dihydrides to monohydrides due to hydrogen desorption. Our results thus provide the first visualization of the SiNC electronic structure evolution induced by dehydrogenation and provide direct evidence for the existence of diverse dangling bond states on the SiNC surfaces.

Na(4)Si(4) and Na(4)Ge(4) are ideal chemical precursors for inorganic clathrate structures, clusters, and nanocrystals. The monoclinic Zintl phases, Na(4)Si(4) and Na(4)Ge(4), contain isolated homo-tetrahedranide [Si(4)](4-) and [Ge(4)](4-) clusters surrounded by alkali metal cations. In this study, a simple scalable route has been applied to prepare Zintl phases of composition Na(4)Si(4) and Na(4)Ge(4) using the reaction between NaH and Si or Ge at low temperature (420 degrees C for Na(4)Si(4) and 270 degrees C for Na(4)Ge(4)). The method was also applied to K(4)Ge(4), using KH and Ge as raw materials, to show the versatility of this approach. The influence of specific reaction conditions on the purity of these Zintl phases has been studied by controlling five factors: the method of reagent mixing (manual or ball milled), the stoichiometry between raw materials, the reaction temperature, the heating time and the gas flow rate. Moderate ball-milling and excess NaH or KH facilitate the formation of pure Na(4)Si(4), Na(4)Ge(4) or K(4)Ge(4) at 420 degrees C (Na(4)Si(4)) or 270 degrees C (both M(4)Ge(4) compounds, M = Na, K). TG/DSC analysis of the reaction of NaH and Ge indicates that ball milling reduces the temperature for reaction and confirms the formation temperature. This method provides large quantities of high quality Na(4)Si(4) and Na(4)Ge(4) without the need for specialized laboratory equipment, such as Schlenk lines, niobium/tantalum containers, or an arc welder, thereby expanding the accessibility and chemical utility of these phases by making them more convenient to prepare. This new synthetic method may also be extended to lithium-containing Zintl phases (LiH is commercially available) as well as to alkali metal-tetrel Zintl compounds of other compositions, e.g. K(4)Ge(9).

Crystals of the title compounds were grown solvothermally in an ethanol–water solvent mixture using ruthenium triiodide, 2,2′-bipyridine and bismuth triiodide as starting materials. Tetra­kis[2-(2-pyridyl)pyridinium] tetra-μ3-iodo-hexa-μ2-iodo-dodeca­iodo­hexa­bismuthate, (C10H9N2)4[Bi6I22], crystallizes in the triclinic space group P\overline{1} and is the major reaction product. The asymmetric unit of this compound consists of half a centrosymmetric [Bi6I22]4− anion and two independent 2,2′-bipyridinium cations. The minor product of the reaction is bis­[tris­(2,2′-bipyridine)ruthenium(II)] di-μ4-iodo-octa-μ2-iodo-dodeca­iodo­hexa­bismuthate, [Ru(C10H8N2)3]2[Bi6I22], which also crystallizes in the triclinic space group P\overline{1}. For this compound, the asymmetric unit consists of one full [Ru(2,2′-bipyridine)3]2+ cation and half a centrosymmetric [Bi6I22]4− anion. Although both compounds contain a centrosymmetric [Bi6I22]4− anion, the polyhedral arrangement of the distorted BiI6 octa­hedra in the two compounds is quite different, and the anion of the latter compound has not previously been observed in iodo­bismuthate chemistry.

Three new hybrid inorganic-organic salts containing novel mixed haloanions of bismuth were synthesized by the solvothermal reaction of bismuth iodide with a haloacid, HX (X = Cl or Br), and the alkylamine 4,4'-trimethylenedipiperidine (TMDP). All three compounds were structurally characterized by single-crystal X-ray diffraction. Reaction of TMDP and BiI(3) with HCl yielded two crystalline products: [H(2)TMDP](2)[(Bi(2)I(9))(BiCl(2)I(2))] (1, major yield) and [H(2)TMDP](2)[Bi(2)Cl(10-x)I(x)] (2, x = 3.83, minor yield). Compound 1 crystallizes in the monoclinic space group Cc (a = 22.8586(11) A, b = 15.5878(7) A, c = 17.6793(9) A, beta = 118.7010(10) degrees , Z = 4) and contains the mononuclear mixed-halide anion BiCl(2)I(2)(-) in addition to a face-sharing bioctahedral Bi(2)I(9)(3)(-) anion and two independent H(2)TMDP(2+) cations. The BiCl(2)I(2)(-) anion has a sawhorse geometry (equatorially vacant trigonal bipyramidal geometry) that is not commonly observed in bismuth chemistry. Compound 2 crystallizes in the monoclinic space group P2(1)/c (a = 14.9471(7) A, b = 12.7622(6) A, c = 13.3381(7) A, beta = 116.1030(10) degrees , Z = 2) and contains an edge-sharing bioctahedral mixed-halide anion in which iodide occupies one and chloride occupies two of the five crystallographically independent halide sites. The remaining two sites have mixed-chloride and -iodide occupancy. Reaction of TMDP and BiI(3) with HBr yielded the crystalline product [H(2)TMDP][BiBr(5-x)I(x)] (3, x = 0.99), which contains, in addition to the organic cation, a polymeric, mixed-haloanion of bismuth(III). Compound 3 crystallizes in the chiral, orthorhombic space group P2(1)2(1)2(1) (a = 8.5189(5) A, b = 14.8988(9) A, c = 17.9984(11) A, Z = 4) and consists of an H(2)TMDP(2+) cation in addition to the anion, which is built up of corner-sharing BiX(6) octahedra. Of the five crystallographically independent halide sites in this anion, two are occupied solely by Br and the remaining three have mixed-bromide and -iodide occupancy. Other anion stoichiometries have been observed crystallographically for 3, as the specific stoichiometry is dependent on the relative concentration of the haloacid starting material used.

The asymmetric unit of the title compound, [Co(C12H8N2)3](I3)2, contains one [Co(1,10-phenanthroline)3]2+ cation, half each of two centrosymmetric triiodide anions, and one complete triiodide anion. The title compound was synthesized solvothermally from Co(NO3)2, 1,10-phenanthroline, and SnI2, where the SnI2 reagent serves only as a source of I atoms.