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The current trend in the miniaturization of electronic devices has driven the investigation into many nanostructured materials. The ferroelectric material barium titanate (BaTiO 3 ) has garnered considerable attention over the past decade owing to its excellent dielectric and ferroelectric properties. This has led to significant progress in synthetic techniques that yield high quality BaTiO 3 nanocrystals (NCs) with well-defined morphologies ( e.g. , nanoparticles, nanorods, nanocubes and nanowires) and controlled crystal phases ( e.g. , cubic, tetragonal and multi-phase). The ability to produce nanoscale BaTiO 3 with controlled properties enables theoretical and experimental studies on the intriguing yet complex dielectric properties of individual BaTiO 3 NCs as well as BaTiO 3 /polymer nanocomposites. Compared with polymer-free individual BaTiO 3 NCs, BaTiO 3 /polymer nanocomposites possess several advantages. The polymeric component enables simple solution processibility, high breakdown strength and light weight for device scalability. The BaTiO 3 component enables a high dielectric constant. In this review, we highlight recent advances in the synthesis of high-quality BaTiO 3 NCs via a variety of chemical approaches including organometallic, solvothermal/hydrothermal, templating, molten salt, and sol–gel methods. We also summarize the dielectric and ferroelectric properties of individual BaTiO 3 NCs and devices based on BaTiO 3 NCs via theoretical modeling and experimental piezoresponse force microscopy (PFM) studies. In addition, viable synthetic strategies for novel BaTiO 3 /polymer nanocomposites and their structure–composition–performance relationship are discussed. Lastly, a perspective on the future direction of nanostructured BaTiO 3 -based materials is presented. 

We report a viable route to plasmonic nanoparticles with well-controlled sizes, shapes, and compositions. A series of monodisperse Ag and Au nanoparticles capped with polystyrene chains ( i.e. , “hairy” nanoparticles) are crafted by capitalizing on star-like diblock copolymers as nanoreactors. Such monodisperse nanoparticles render an accurate absorption spectrum, providing a strong basis for theoretical investigation into their optical properties. By combining the experimental study with the three-dimensional finite element calculation of electromagnetic field distributions, the contributions of both intra-band and inter-band transitions to plasmonic absorption are revealed. The calculated absorption spectra perfectly reproduce the experimental observations, including the peak positions, shapes, and trends of peak shifting or broadening as a function of nanoparticle sizes. The influences of nanoparticle dimensions and surface ligands on plasmonic absorption of metallic nanoparticles are also systematically explored. 

Facile and large-scale synthesis of well-defined, thermally stable silver nanoparticles protected by polymer brushes for use in practical applications is still a challenge. Recent work has reported a nanoreactor approach that can be used to synthesize these silver nanoparticles. This approach uses amphiphilic star-block copolymers, which have a hydrophilic core surrounded by a hydrophobic exterior. These polymers thus can serve as the nanoreactors. In this study, we hypothesize that the local high concentration of silver ions in the inner hydrophilic cores of these star-block copolymers facilitates the nucleation and subsequent growth of silver nanoparticles. When all silver nanoparticles nucleate from the cores of the star-block copolymers in solution, the particle size can be controlled by the core size of the polymer. To test this hypothesis, a polyisoprene-b-poly(p-tert-butylstyrene) (PI-b-PtBS) star-block copolymer was functionalized with carboxylic acid groups using a high-efficiency, photo-initiated thiol-ene click reaction. We characterized this modified polymer using proton nuclear magnetic resonance spectroscopy, and the results indicated that ~60% of the double bonds in the polyisoprene block were successfully functionalized with carboxylic acid groups. When silver ions were added to a solution of these functionalized star-block copolymers, the negatively charged carboxylic acid groups would attract the positively charged silver ions. Subsequent reduction of these Ag+ by a tert-butylamine-borane complex at room temperature produced nanosized silver particles. However, transmission electron microscopy images showed that a significant amount of relatively large silver nanoparticles grew outside the star-block copolymer nanoreactors.