Paramagnetic ultrasmall gadolinium oxide (Gd(2)O(3)) nanoparticles with particle diameters (d) of approximately 1 nm were synthesized by using three kinds of Gd(III) ion precursors and by refluxing each of them in tripropylene glycol under an O(2) flow. A large longitudinal relaxivity (r(1)) of water proton of 9.9 s(-1) mM(-1) was estimated. As a result, high contrast in vivo T(1) MR images of the brain tumor of a rat were observed. This large r(1) is discussed in terms of the huge surface to volume ratio (S/V) of the ultrasmall gadolinium oxide nanoparticles coupled with the cooperative induction of surface Gd(III) ions for the longitudinal relaxation of a water proton. It is found from the d dependence of r(1) that the optimal range of d for the maximal r(1), which may be used as an advanced T(1) MRI contrast agent, is 1-2.5 nm.

Enhanced power conversion efficiency (PCE) is reported in inverted polymer solar cells when an electron‐rich polymer nanolayer (poly(ethyleneimine) (PEI)) is placed on the surface of an electron‐collecting buffer layer (ZnO). The active layer is made with bulk heterojunction films of poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM). The thickness of the PEI nanolayer is controlled to be 2 nm to minimize its insulating effect, which is confirmed by X‐ray photoelectron spectroscopy and optical absorption measurements. The Kelvin probe and ultraviolet photoelectron spectroscopy measurements demonstrate that the enhanced PCE by introducing the PEI nanolayer is attributed to the lowered conduction band energy of the ZnO layer via the formation of an interfacial dipole layer at the interfaces between the ZnO layer and the PEI nanolayer. The PEI nanolayer also improves the surface roughness of the ZnO layer so that the device series resistance can be noticeably decreased. As a result, all solar cell parameters including short circuit current density, open circuit voltage, fill factor, and shunt resistance are improved, leading to the PCE increase up to ≈8.9%, which is close to the best PCE reported using conjugated polymer electrolyte films.

Creating a good image: A probe for combined positron emission tomography (PET) and magnetic resonance imaging (MRI) has high colloidal stability and demonstrates facile conjugation ability. Sentinel lymph nodes are clearly identified in the fusion image (see picture; I: injection site) because of the complementary nature of the techniques, which makes accurate anatomical information and fault‐free diagnosis possible.

For the application of superparamagnetic iron oxide nanoparticles in biomedical fields for target-specific purposes, they should be ultra small in diameter. We developed a simple one-step synthesis of surface modified ultra small superparamagnetic iron oxide nanoparticles (USPIONs) with an average particle diameter of 1.7 nm in a polar organic solvent. Polyethylene glycol diacid (PEG) surface modified USPIONs synthesized in triethylene glycol were nearly monodisperse in diameter and highly water-dispersible. The PEG surface modified USPIONs were tested for use as magnetic resonance (MR) contrast agents. They had a low r(2)/r(1) relaxivity ratio of 3.4 (r(1) = 4.46 and r(2) = 15.01 mM(-1) s(-1)) and showed clear dose-dependent T(1) and T(2) map images, indicating that they will be useful as both target-specific T(1) and T(2) MR contrast agents due to their ultra small size.

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Creating a good image: A probe for combined positron emission tomography (PET) and magnetic resonance imaging (MRI) has high colloidal stability and demonstrates facile conjugation ability. Sentinel lymph nodes are clearly identified in the fusion image (see picture; I: injection site) because of the complementary nature of the techniques, which makes accurate anatomical information and fault‐free diagnosis possible.

Polymer solar cells have been spotlighted due to their potential for low-cost manufacturing but their efficiency is still less than required for commercial application as lightweight/flexible modules. Forming a dipole layer at the electron-collecting interface has been suggested as one of the more attractive approaches for efficiency enhancement. However, only a few dipole layer material types have been reported so far, including only one non-ionic (charge neutral) polymer. Here we show that a further neutral polymer, namely poly(2-ethyl-2-oxazoline) (PEOz) can be successfully used as a dipole layer. Inclusion of a PEOz layer, in particular with a nanodot morphology, increases the effective work function at the electron-collecting interface within inverted solar cells and thermal annealing of PEOz layer leads to a state-of-the-art 10.74% efficiency for single-stack bulk heterojunction blend structures comprising poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] as donor and [6,6]-phenyl-C71-butyric acid methyl ester as acceptor.

We report the influence of the controlled acidity of the hole-collecting buffer layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), on the performance and lifetime of polymer:fullerene solar cells. The acidity was controlled by adding a strong base (NaOH) to the pristine PEDOT:PSS solutions. The NaOH-modified PEDOT:PSS layers were used for fabricating polymer:fullerene solar cells with active layers made from blend films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). The results showed that a small addition of NaOH (0.2 molar ratio) removed 23% of the sulfonic acid groups but did not change the device performance, even though further NaOH addition degraded the device performance owing to an increased sheet resistance and lowered work function, as well as a changed surface morphology. Storage lifetime tests showed that the device with the modified PEDOT:PSS layer (0.2 molar ratio NaOH) was almost not degraded, whereas the pristine PEDOT:PSS layer might affect the deterioration at the interface with the active layer (P3HT:PCBM). Under 1 sun illumination for 10 h, the modified PEDOT:PSS layer (0.2 molar ratio NaOH) resulted in ∼25% improved lifetime, which is in excellent agreement with the extent of reduction of the sulfonic acid groups (∼23%).