Ultrasmall fluorescent silica nanoparticles (SNPs) and core−shell SNPs surface functionalized with polyethylene glycol (PEG), specific surface ligands, and overall SNP size in the regime below 10 nm are of rapidly increasing interest for clinical applications, because of their favorable biodistribution and safety profiles. Here, we present an aqueous synthesis methodology for the preparation of narrowly size-dispersed SNPs and core−shell SNPs with size control below 1 nm, i.e., at the level of a single atomic layer. Different types of fluorophores, including near-infrared (NIR) emitters, can be covalently encapsulated. Brightness can be enhanced via addition of extra silica shells. This methodology further enables synthesis of <10 nm sized fluorescent core and core−shell SNPs with previously unknown compositions. In particular, the addition of an aluminum sol gel precursor leads to fluorescent aluminosilicate nanoparticles (ASNPs) and core−shell ASNPs. Encapsulation efficiency and brightness of highly negatively charged NIR fluorophores is enhanced, relative to the corresponding SNPs without aluminum. Resulting particles show quantum yields of ∼0.8, i.e., starting to approach the theoretical brightness limit. All particles can be PEGylated providing steric stability. Finally, heterobifunctional PEGs can be employed to introduce ligands onto the PEGylated particle surface of fluorescent SNPs, core−shell SNPS, and their aluminum-containing analogues, producing ligand-functionalized <10 nm NIR fluorescent nanoprobes. In order to distinguish these water-based-synthesis-derived materials from the earlier alcohol-based modified Stober process derived fluorescent core−shell SNPs referred to as Cornell dots or C dots, the SNPs and ASNPs described here and synthesized in water will be referred to as Cornell prime dots or C′ dots and AlC′ dots. These organic−inorganic hybrid nanomaterials may find applications in nanomedicine, including cancer diagnostics and therapy (theranostics).

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Reaction of at ethered triamine ligand with Bi-(NMe 2 ) 3 gives aBitriamide,for which aBi I electronic structure is shown to be most appropriate.T he T-shaped geometry at bismuth provides the first structural model for edge inversion in bismuthines and the only example of aplanar geometry for pnictogen triamides.A nalogous phosphorus compounds exhibit ad istorted pyramidal geometry because of different BiÀNa nd PÀNb ond polarities.A lthough considerable Bi I character is indicated for the title Bi triamide,i te xhibits reactivity similar to Bi III electrophiles,a nd expresses either avacant or afilled porbital at Bi, as evidenced by coordination of either pyridine N-oxideo rW (CO) 5 .T he product of the former shows evidence of coordination-induced oxidation state change at bismuth. Scheme 1. Synthesis of low-oxidation-state p-block complexes by either external reductants or redox-active ligands.

ABSTRACT:The coefficient of thermal expansion of ZrMgMo 3 O 12 has been measured and was found to be extremely close to zero over a wide temperature range including room temperature (α = (1.6 ± 0.2) × 10 −7 K −1 from 25 to 450°C by X-ray diffraction (XRD)). ZrMgMo 3 O 12 belongs to the family of AMgM 3 O 12 materials, for which coefficients of thermal expansion have previously been reported to range from low-positive to low-negative. However, the low thermal expansion property had not previously been explained because atomic position information was not available for any members of this family of materials. We determined the structure of ZrMgMo 3 O 12 by nuclear magnetic resonance (NMR) crystallography, using 91 Zr, 25 Mg, 95 Mo, and 17 O magic angle spinning (MAS) and 17 O multiple quantum MAS (MQMAS) NMR in conjunction with XRD and density functional theory calculations. The resulting structure was of sufficient detail that the observed zero thermal expansion could be explained using quantitative measures of the properties of the coordination polyhedra. We also found that ZrMgMo 3 O 12 shows significant ionic conductivity, a property that is also related to its structure.

Mesoporous silica nanoparticles (MSNs) have recently attracted a lot of interest for future nanotheranostic applications because of their large surface-area and high biocompatibility. However, studies to date of MSNs are confined to >10 nm particle sizes which may result in unfavorable biodistribution characteristics for in vivo experiments and hence limit their clinical applications. Here we provide a full account of a synthesis approach to ultrasmall sub-10 nm mesoporous silica nanoparticles with narrow size distributions and homogeneous porous particle morphology. Key features enabling this structure control are (i) fast hydrolysis, (ii) slow condensation, and (iii) capping of particle growth by addition of a PEG-silane at different time-points of the synthesis. Variation of synthesis conditions including monomer/catalyst concentrations, temperature, and time-point of PEGsilane addition leads to synthesis condition-particle structure correlations as mapped out by a combination of results from data analysis of dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. Results establish precise control over average particle diameter from 6 to 15 nm with increments below 1 nm. Solid state nuclear magnetic resonance (NMR) measurements, zeta-potential measurements, and thermogravimetric analysis (TGA) were conducted to reveal details of the particle surface structure. Long-term particle stability tests in deionized (DI) water and phosphate buffered saline (PBS) 1X buffer solution were performed using DLS demonstrating that the PEGylated particles are stable in physiological environments for months. Fluorescent single pore silica nanoparticles (mC dots) encapsulating blue (DEAC) and green (TMR) dyes were synthesized and characterized by a combination of DLS, TEM, static optical spectroscopy, and fluorescence correlation spectroscopy (FCS) establishing probes for multicolor fluorescence imaging applications. The ultraprecise particle size control demonstrated here in particular for sizes around and below 10 nm may render these particles an interesting subject for further fundamental studies of porous silica particle formation mechanisms as well as for sensing, drug delivery, and theranostic applications.