Reviews & Analysis

Upconversion nanophosphors have unique ability to generate anti-Stokes luminescence. The rapid developments of nanotechnology in recent years have demonstrated the successful synthesis and optimization of such upconversion nanophosphors. This review summarizes the recent advances using upconversion nanophosphors as bioprobe for in vivo applications.

Seven years ago, Wilma Eerenstein, Neil Mathur and Jim Scott published a Venn diagram (above) showing the overlap of piezoelectricity, ferroelectricity (green circle), ferromagnetism (black circle), and magnetoelectricity (blue hatched center circle); and soon thereafter Manuel Bibes put into each sector the crystals which were thought to belong. The overlap region between green and black are multiferroic ferromagnetic-ferroelectrics. Not all were correct; BiMnO₃ is NOT ferroelectric. Of these materials, only Cr₂O₃ and BiFeO₃ function at room temperature (or are magnetoelectric, and the former is neither a ferromagnet nor ferroelectric). Today’s review is an update on the new multiferroic and/or magnetoelectric materials that function at or near ambient temperatures and pressures: Cupric oxide (not actually magnetoelectric), iron magnesium hexaferrites, and perovskite oxides based upon PbTiO₃.

Metal chalcogenide quantum dots (QDs) and lead halide perovskites are two types of prospective light harvesters for mesoscopic solar cells. The two most promising QD sensitizers are PbS and Sb₂S₃, for which the PCEs of their corresponding QDSCs have attained ∼7% in 2012. In 2013, the performance of a TiO₂ solar cell sensitized with lead-iodide perovskite (CH₃NH₃PbI₃) was optimized to attain an overall power conversion efficiency of 15%, which is a new milestone for solar cells of this type, with a device structure similar to that of a dye-sensitized solar cell.

Plasmonic photoelectric conversion from visible to near-infrared wavelengths has been successfully demonstrated using electrodes in which gold nanorods are elaborately arrayed on a titanium dioxide (TiO₂) single crystal. Importantly, water molecules serve as the electron donor in the plasmonic photoelectric conversion system. Therefore, the stoichiometric evolution of oxygen and hydrogen peroxide as a result of the four- or two-electron oxidation of water molecules was accomplished even at near-infrared wavelengths, enabling the application of this plasmonic photoelectric system in artificial photosynthesis processes responding to a wide range of solar wavelengths.

Over the last decade, metal oxides have proven to be important materials for organic electronics. Oxides are often used as charge-injection and charge-selective interlayers to engineer the electrical resistance at electrode/organic interfaces in organic devices. An oxide’s behavior as an interlayer depends strongly on the oxide’s electronic properties—such as its band structure and work function. The numerous degrees of freedom in an oxide’s electronic properties allow these characteristics to be easily modified. The present review outlines the use of metal oxides in organic electronics, and discusses the factors that affect the oxide’s properties that are relevant to oxide/organic interfaces.

Along with the rapid merge and development of biotechnology and nanotechnology, various DNA nanostructure scaffolds have been designed, characterized and exploited for a range of applications. Particularly, we have seen the evolution of surface-confined DNA probes with rational design from one-dimensional to two-dimensional and then to three-dimensional, which greatly improve our ability to control the density, orientation and passivation of the surface. In this review, we aim to summarize recent progress on the improvement of probe–target recognition properties by introducing DNA nanostructure scaffolds. A range of new strategies have proven to provide significantly enhanced spatial positioning range and accessibility of the probes on surface over previously reported linear structures. We will also describe applications of DNA nanostructure scaffold-based biosensors.

Lipid-nanostructure hybrids possess dimensions that are comparable to biological molecules as well as unique and useful physicochemical properties arising from both lipids and nanomaterials. Therefore, the hybrids allow mimicking of the assembled structure and function of subcellular membrane components and monitoring of the membrane-associated reactions in a highly sensitive and controllable manner. In this review, we present recent advances in the synthesis of various lipid-nanostructure hybrids and the use of these structures for applications in nanobiotechnology. We further describe the scientific and practical applications of lipid-nanostructure hybrids for detecting membrane-targeting molecules, interfacing nanostructures with live cells and creating membrane-mimicking platforms to investigate cell–cell communication and intracellular processes.

Poly(3-hexylthiophene) nanowires, microns in length and nanometers in diameter, are stably suspended in solution, and crystallize by adjusting solvent strength. Cocrystalization of P3HT with P3HT-covered CdSe nanorods gave hybrid nanostructures in which the p-type P3HT fibrils were flanked by the n-type CdSe nanorods. The close proximity and arrangement of the two materials provides direct, continuous pathways suitable for charge transport in photovoltaic devices.

In this review, nanoporous thin-film template was obtained from the self-assembly of block copolymer PS-PLLA, at which the PLLA block can be hydrolyzed to form the nanopatterns. Nanoporous PS thin films with well-oriented cylinder nanochannels can be used for pore-filling with various ingredients to create specific drug delivery systems and optoelectronic devices. Moreover, nanoporous ceramics with high-specific surface area and high porosity can be fabricated for optical applications using hydrolyzed gyroid-forming PS-PLLA for templated sol–gel reaction. In addition, the formation of inorganic nanoporous templates from self-assembled PS-PDMS after oxygen plasma treatment and its corresponding applications in nanolithography will be discussed.

Nanostructured materials always exhibit high strength, ultra-large elasticity and unusual plastic deformation behaviors. The atomic-scale understanding of the microstructure evolution process of nanomaterials when they are subjected to external stress is crucial for understanding these ‘unusual’ phenomena and is important for designing new materials and applications. In situ transmission electron microscopy (TEM) experiments provide the possibility for direct observation of the deformation mechanisms at the atomic scale. This review presents the recent developments of techniques and scientific progress for the atomic-scale in situ TEM deformation dynamics on nanomaterials. Current limitations and future aspects are also discussed.