Functionalization of ultrasmall semiconductor nanoparticles to develop new luminescent probes that are optically bright, stable in aqueous environments, and sized comparably to small organic fluorophores would be of considerable utility for myriad applications in biology. Here, we report one of the first examples of thermal hydrosilylation between a bi-functional alkene and ultrasmall (y1 nm) H-passivated silicon nanoparticles (Si-np-H) to prepare strongly luminescent, water stable, carboxyl functionalized nanoparticles (Si-np-COOH). Nuclear magnetic resonance, infrared absorption spectroscopy (FTIR), size exclusion chromatography (SEC), and photoluminescence spectroscopy are used to characterize the Si-np dispersions. Based on the SEC and FTIR data, a reaction scheme is proposed to account for side products formed through a free radical cross-linking mechanism. The Si-np-COOH may find use in applications such as biomolecular labeling and biological imaging.

Ultrabright ultrasmall ͑ϳ1 nm͒ blue luminescent Si 29 nanoparticles are chlorinated by reaction with Cl 2 gas. A SiN linkage is formed by the reaction of the chlorinated particles with the functional amine group in butylamine. Fourier transform infrared spectroscopy and x-ray photospectroscopy measurements confirm the N linkage and the presence of the butyl group, while emission, excitation, and autocorrelation femtosecond optical spectroscopy show that, after the linkage formation, the particles with the ultrabright blue luminescent remain, but with a redshift of 40 nm.

A Si 29 H 24 particle, with five atoms constituting a tetrahedral core and 24 atoms constituting a H-terminated reconstructed Si surface was recently proposed as a structural prototype of ultrasmall ultrabright particles prepared by electrochemical dispersion from bulk Si. We replace the H termination with a N linkage ͑in butylamine͒ and O linkage ͑in pentane͒. The emission band for N-termination downshifts by ϳ0.25 eV from that of H termination, whereas it blueshift ϳ0.070 eV for C termination. We use density-functional approaches to calculate the atomic structures and correction from the quantum Monte Carlo method to estimate the highest occupied-lowest unoccupied molecular-orbital band gap. We find a downshift of 0.25 eV for N termination and very little for C termination. These features are discussed in terms of exciton penetration in the capping material.

Studying the properties and stability of silicon nanoparticles (Si-np) in aqueous environments may lead to novel applications in biological systems. In this work, we use absorption and photoluminescence (PL) spectroscopy to characterize ultrasmall Si-np prepared through anodic etching and ultrasonic fractionation of a crystalline Si wafer. Their behavior is studied over time in 2-propanol and during treatments with water, NaOH, HCl, and H 2 O 2 . The observed population is divided into two types of material: bright species consisting of well-etched Si-np, ∼1 nm in diameter, and dark species derived from partially etched or aggregated Si structures. The dark material is seen by its scattering in the 2-propanol and water solutions and is largely removed via precipitation with the NaOH or HCl treatment. The bright material includes three distinct species with their respective emissions in the UV-B, UV-A, and hard-blue regions of the spectrum. The hard-blue PL is shown to have a simple pH dependence with a pK a ∼3, providing an important insight into its chemical origin and signaling for possible application of Si-np as environmental probes. Our results offer some potential for tailoring the PL properties of ultrasmall Si-np through control of their surface chemistry.

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New block copolymers based on the ionogenic block of poly(N,N-diallyl-N,N-dimethylammonium chloride) (PDADMACl) and liquid crystalline (LC) acrylate-based polymers are synthesized. The chain length of the acrylate-based block is controlled by the temperature and PDADMACl−acrylic monomer ratio. The chain length of the acrylate-based block controls the structure of the PDADMACl block whether crystalline or amorphous. Because of the “solid” state of the polyelectrolyte in domains both polymer and small ions are strongly fixed, and this provides the opportunity to reveal the polymer chain dynamics related with the LC acrylate-based polymer. The dynamics of the LC polymer in the block-copolymer is shown to be very similar to that in the homopolymer with no strong influence of polyelectrolyte blocks.

The ionogenic polymers namely poly(N,N‐diallyl‐N‐cetylammonium hydronitrate) (PDACA · HNO3) and poly(N,N‐diallyl‐N,N‐dimethylammonium chloride)‐block‐poly(cetyl acrylate) (PDADMACl‐block‐PA‐16) were synthesized via activation of the terminal double bond of the PDADMACl precursor and initiation of the polymerization of the acrylic monomer in alcohol solution. The microphase separated structure of a blend of both homopolymers and of the block copolymer was proved by differential scanning calorimetry (DSC) and X‐ray diffraction measurements. Side chain crystallization in PDA‐CA · HNO3 completely restricts the crystallization of the ionogenic backbones which, however, control the layered structure and the crystallization of the aliphatic chains. In PDADMACl‐block‐PA‐16 crystalline polyacrylate blocks coexist with crystalline ionogenic blocks. The length of the polyacrylate block influences the ability of the ionogenic block to form the crystalline structure.

SUMMARY The ionogenic polymers namely poly(N,N-diallyl-N-cetylammonium hydronitrate) (PDACA HN03) and poly~N,N-diallyl-~,N-~methyl~monium chloride)-bZoc~-poly(cetyl acrylate) (PDADMAC1-block-PA-16) were synthesized via activation of the terminal double bond of the PDADMACl precursor and initiat~on of the polyme~zation of the acrylic monomer in alcohol solution. The microphase separated structure of a blend of both homopolymers and of the block copolymer was proved by differential scanning calorimetry (DSC) and X-ray diffraction measurements. Side chain crystallization in PDA-CA -HN03 completely restricts the crystallization of the ionogenic backbones which, however, control the layered structure and the crystallization of the aliphatic chains. In PDADMAC1-block-PA-16 crystalline polyacrylate blocks coexist with crystalline ionogenic blocks. The length of the polyacrylate block influences the ability of the ionogenic block to form the crystalline structure.