To explore the possibility of cluster assembly resulting in a two-dimensional (2D) stable monolayer of ZnO, a systematic study is performed on the structural evolution of bare and passivated stoichiometric clusters of [Formula: see text] [Formula: see text], [Formula: see text], using density-functional-theory-based first principles electronic structure calculations. The changes in hybridization are investigated with the aid of the site-projected partial density of states and partial charge density, while the effect of passivation and size on the ionicity of the cluster is studied using Bader charge analysis. The structural and chemical properties are found to be influenced by the coordination number of atoms in the clusters irrespective of the coordinating species. The physical parameters and hybridization of the states for the clusters on passivation resemble those of the bulk. Passivation thus provides an environment that leads to the stability of the clusters. Cluster assembly using the stable cluster geometries of passivated clusters (without the passivating atoms) has been shown to lead to stable 2D structures. This stability has been studied on the basis of binding energy, vibrational frequency, phonon dispersion and thermal properties. A new octagonal 2D monolayer planar geometry of ZnO is predicted.

Strong, directional, N bonding led surface stabilization is induced to obtain free-standing two-dimensional (2D) layered assemblies of Lonsdaleite and diamondphase carbon by surface termination at three coordinated C sites. These assemblies have strong bonding and surface N lone pair induced self-protection and achieve respective bulklike electronic, mechanical, and crystallographic properties at as low as seven atomic layer thickness. Lonsdaleite phase subnano thickness free-standing as small as three layered assembly shows bulk-like thermal stability up to 2900 K. Size confinement effect dominates up to four layered assembly, and then electronic and crystallographic properties are dominated by bulk stabilization which saturates toward respective bulk-like features from seven layered assembly. Similarly, free-standing hybrid assemblies of Lonsdaleite phase carbon with BeF (C 5 NBeF) and BS (C 5 NBS) layer are also proposed along with low symmetric Cm-C 3 N 4 layered assembly. The combination of N and O is shown to stabilize the surface of nanodiamond but shows significant variation in structural and electronic properties, which are principally governed by the confinement effect because of weak surface stabilization. Our results propose that, in principle, 2D free-standing layered assemblies of the sp 3 hybridized phases of carbon with surface terminated by only three coordinated C sites can be stabilized and engineered by substitutional doping of N, and in some cases, respective bulk-like electronic and crystallographic properties at nanosize can be achieved.

Confinement of polymer chains in polymer nanocomposites influences their dynamics leading to the changes in their molecular packing compared to pure polymer. In order to study the exclusive effects of confinement on molecular packing of poly vinyl alcohol (PVA) chains, PVA nanocomposite films with varying (wt%) gold nanoparticles (Au NPs) were prepared using simple solution casting method. The triplet state of positronium (ortho-positronium, o-Ps) was used as a probe for determination of sub nano level free volume holes' size, density, and size distribution. The study shows that molecular packing (free volume characteristics) is exclusively modified due to the confinement of PVA chains though there is no direct interfacial interaction between PVA and Au NPs. The changes are suppressed at highest studied Au NPs loading (0.60 wt%) mainly due to nanoparticle aggregation leading to an increase in the inter particle distance, a parameter which quantitatively defines the effect of confinement in polymer nanocomposites. X-ray diffraction (XRD) and Fourier transformed infra-red (FTIR) measurements were carried out to index the crystallinity and hydrogen bonding of PVA matrix. The variation in thermo-mechanical properties (Young's modulus and glass transition temperature) of the nanocomposite is explained considering the changes in molecular packing and crystallinity of PVA matrix. POLYM. COMPOS., 00:000-000,

Size confinement for tailoring of electronic structures can in principle be explored for enhancement of photocatalytic properties. In the present work, vanadium-doped bismuth oxide nanoparticles, with an average particle size of 36 nm, are synthesized for the first time, using the thermal plasma method, in large scale with high yield to explore for photocatalytic applications. The electronic and crystallographic structures of the sample are studied experimentally and theoretically. Systematic investigations of the electronic structure of the fluorite type cubic phase of Bi 11 VO 19 nanoparticles are reported for the first time. Enhancement is observed in the photocatalytic activity as compared to other delta phases of bismuth vanadate. The valence band is found to comprise mainly of O 2p states, whereas the conduction band arises from V 3d states giving rise to a band gap value of 2.26 eV. Absence of excess O in δ-Bi 2 O 3 results in shrinking of the band gap because of O 2p, Bi 6s and 6p states from the surrounding atoms at doping sites. Bi 11 VO 19 nanoparticles show an efficient visible light absorption and exhibit excellent photodegradation properties of methylene blue solution under visible light irradiation.