There has been an increasing interest in the past few years in the synthesis of ferroelectric nanocrystals because of their scientific importance and widespread applications in electronics, sensing, catalysis, and nonlinear optics. 1 BaTiO 3 is a perovskite-type ceramic with unique mechanical, ferroelectric, electro-optic, pyroelectric, dielectric, and elastic properties that find use in multilayered capacitors, random access memories, thermistors, photonic crystals, pressure transducers, and waveguide modulators. 2 It is well-known that perovskite nanocrystals possess structural and physical properties that are strongly dependent on their size, shape, crystallinity, and surface composition. For example, in nanoscale BaTiO 3 , the transition temperature from the ferroelectric (tetragonal) to the paraelectric (cubic) phase decreases progressively with the size of the particles as a result of a less distorted coordination environment of the Ti 4þ ions within the TiO 6 octahedra. However, there is no clear consensus as to the critical size at which ferroelectricity is suppressed, and consequently, the values reported extend over a wide range, typically from 120 to 4.2 nm. 3 Despite the increasing number

Increasing biomedical applications of iron oxide nanoparticles (IONPs) in academic and commercial settings have alarmed the scientific community about the safety and assessment of toxicity profiles of IONPs. The great amount of diversity found in the cytotoxic measurements of IONPs points toward the necessity of careful characterization and quantification of IONPs. The present document discusses the major developments related to in vitro and in vivo toxicity assessment of IONPs and its relationship with the physicochemical parameters of IONPs. Major discussion is included on the current spectrophotometric and imaging based techniques used for quantifying, and studying the clearance and biodistribution of IONPs. Several invasive and non-invasive quantification techniques along with the pitfalls are discussed in detail. Finally, critical guidelines are provided to optimize the design of IONPs to minimize the toxicity.

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Methods have been developed for the shape-selective synthesis of ferroelectric LiNbO 3 nanoparticles. Decomposition of the single-source precursor, LiNb(O-Et) 6 , in the absence of surfactants, can reproducibly lead to either cube-or sphere-like nanoparticles. X-Ray diffraction shows that the LiNbO 3 nanoparticles are rhombohedral (R3c). Sample properties were examined by piezoresponse force microscopy (PFM) and Raman where both sets of nanoparticles exhibit ferroelectricity. The longitudinal piezoelectric coefficients, d 33 , varied with shape where the largest value was exhibited in the nanocubes (17 pm V 21 for the cubes versus 12 pm V 21 for spheres).

A versatile method has been developed for the fabrication of magnetic peapod nanocomposites with preformed nanoparticles (NPs). With use of a solvothermal treatment, NPs combined with acid-exchanged hexaniobate crystallites readily produce nanopeapods (NPPs). This approach is effectively demonstrated on a series of ferrite NPs (≤14 nm) where Fe 3 O 4 @hexaniobate NPPs are rapidly (∼6 h) generated in high yield. When NP samples with different sizes are reacted, clear evidence for size selectivity is seen. Magnetic dipolar interactions between ferrite NPs within the Fe 3 O 4 @hexaniobate samples lead to significant rise in coercivity, increasing almost fourfold relative to free particles. Other magnetic ferrites NPPs, MFe 2 O 4 @hexaniobate (M = Mn, Co, Ni), can also be prepared. This synthetic approach to nanopeapods is quite versatile and should be readily extendable to other, nonferrite NPs or NP combinations so that cooperative properties can be exploited while the integrity of the NP assemblies is maintained.

Lead-free 0.5BaZr0.2Ti0.8O3–0.5Ba0.7Ca0.3TiO3 (BZT–BCT) thin films were deposited on Pt(1 1 1)/TiO2/SiO2/Si substrates by pulsed laser deposition. The optimal ferroelectric response with a high saturation polarization Ps ~ 110 µC cm−2, remnant polarization Pr ~ 32.5 µC cm−2 along with a coercive field of 0.18 MV cm−1 was observed from the P–E hysteresis loops under an applied frequency of 1 kHz. A giant recoverable energy-storage density of 93.52 J cm−3 at an applied electric field ~3.47 MV cm−1 was observed. The optimized BZT–BCT thin films exhibited a high dielectric constant with a low dielectric loss at room temperature like their bulk counterpart (high dielectric constant (Ɛ ~ 121 81)) and low dielectric loss (tan δ ~ 0.01–0.03) properties. OPP-PFM images revealed switchable ferroelectric distinct polarization contrasts on the application of a  ±12 V dc voltage on the conductive tip at room temperature. Observed enhanced dielectric, ferroelectric and energy density properties of BZT–BCT thin films are useful for next generation electrical energy storage applications.

A facile in situ method to grow Au nanoparticles (NPs) in hexaniobate nanoscrolls is applied to the formation of plasmonic Au@hexaniobate and bifunctional plasmonic-magnetic Au-Fe3 O4 @hexaniobate nanopeapods (NPPs). Utilizing a solvothermal treatment, rigid multiwalled hexaniobate nanoscrolls and partially filled Fe3 O4 @hexaniobate NPPs were first fabricated. These nanostructures were then used as templates for the controlled in situ growth of Au NPs. The resulting peapod structures exhibited high filling fractions and long-range uniformity. Optical measurements showed a progressive red shift in plasmonic behavior between Au NPs, Au NPPs, and Au-Fe3 O4 NPPs; magnetic studies found that the addition of gold in the Fe3 O4 @hexaniobate NPPs reduced interparticle coupling effects. The development of this approach allows for the routine bulk preparation of noble-metal-containing bifunctional nanopeapod materials.

Polycrystalline gadolinium (Gd) substituted cobalt ferrites (CoFe 2-x Gd x O 4 ; x=0-0.3, referred to CFGO) ceramics have been synthesized by solid state reaction method. Chemical bonding, crystal structure and magnetic properties of CFGO compounds have been evaluated as a function of Gd-content. X-ray diffraction and Raman spectroscopic analyses confirmed the formation of inverse spinel structure. However, a secondary ortho-ferrite phase (GdFeO 3 ) nucleates for higher values of Gd-content. A considerable increase in the saturation magnetization has been observed upon the initial substitution of Gd (x=0.1). The saturation magnetization drastically decreases at higher Gd content (x≥0.3). No contribution from ortho-ferrite GdFeO 3 phase is noted to the magnetic properties. The increase in the magnetic saturation magnetization is attributed to the higher magnetic moment of Gd 3+ (4f 7 ) residing in octahedral sites is higher when compared to that of Fe 3+ (3d 5 ) and as well due to the migration of Co 2+ (3d 7 ) ions from the octahedral to the tetrahedral sites with a magnetic moment aligned anti-parallel to those of rare earth (RE 3+ ) ions in the spinel lattice. Increase in coercivity with increase in Gd 3+ is content is attributed to magnetic anisotropy in the ceramics.