In various cultures, the Lotus plant has been considered to be a symbol of purity for a very long time because the leaves have a natural cleaning mechanism. Instead of wetting the surface, water droplets roll off the leaves' surfaces taking with them dirt and contamination.[1] This so-called Lotus effect is based on the superhydrophobic nature of the surface, realized by the fractal morphology of the two-tier roughness on both micro-and nanometer length scales. In order to artificially mimic water-repellent surfaces, it is necessary to prepare a surface composed of hydrophobic molecular or polymeric building blocks that exhibits a low surface energy and a rough fractal interfacial morphology. [2][3][4][5][6] However, when applying these principles to manufacturing of self-cleaning surfaces, the resulting biomimetic structures additionally have to be durable and stable, which is generally a difficult issue for self-organized supramolecular systems based on weak intermolecular forces. [7][8][9][10] Previously, superhydrophobic surfaces have been prepared using several techniques, such as sol-gel processing, [11,12] fabrication of structures from carbon nanotubes [13,14] and fluorinated polymers, [15] chemical vapor deposition, [16] and so forth. [17,18] To our knowledge fullerenes have not been employed as molecular components for superhydrophobic surfaces so far, even though they are at present one of the most fascinating carbon nanomaterials, [19] and are inexpensive compared to carbon nanotubes. To date, superhydrophobic materials have not been prepared by molecular self-organization in a convincing way. Here, we show for the first time that molecular self-organization of a fullerene derivative leads to macroscopic globular objects with a two-tier roughness on the micro-and nanoscopic length scale. Surfaces resulting from simple casting of these objects are superhydrophobic and surprisingly durable. The fullerene used in the present study is based on C 60 functionalized with three eicosyloxy aliphatic chains (1). Both parts of the molecule are hydrophobic and exhibit low free surface energies, which is one key requirement for the construction of superhydrophobic materials, with high surface roughness being the other criterion. Notably, the strength of the interactions between C 60 moieties and aliphatic chains depends on the environment and, therefore, allows us to control the self-assembly and aggregation behavior through the choice of the solvent. This gives us two independent parameters to manipulate the self-assembly of this class of fullerenes: [20][21][22][23][24][25] i) the design of the derivative, e.g., the number and length of aliphatic chains; and ii) the experimental conditions for self-assembly. Recently, we reported on the hierarchical self-assembly of a fullerene derivative bearing three hexadecyloxy groups furnishing various polymorphs depending on the experimental conditions such as solvent and temperature.[20]The fullerene derivative 1 (Fig. 1a) was prepared by refluxing the corresponding benza...

A novel design of white light emitting diodes (WLEDs) emerges to meet the growing global demand for resource sustainability while preserving health and environment. To achieve this goal, a facile method is developed for the chemical synthesis of a luminescent silicon nanocrystal (ncSi) with a large Stokes shift between absorption and emission. The WLED is prepared by a simple spin‐coating method, and contains a hybrid‐bilayer of the ncSi and luminescent polymer in its device active region. Interestingly, a well‐controlled ultrathin ncSi layer on the polymer makes possible to recombine electrons and holes in both layers, respectively. Combining red and blue‐green lights, emitted from the ncSi and the polymer layers, respectively, produces the emission of white electroluminescence. Herein, a hybrid‐WLED with a sufficiently low turn‐on voltage (3.5 V), produced by taking advantages of the large Stokes shift inherent in ncSi, is demonstrated.

The synthesis of highly luminescent colloidal CsSnX3 (X = halogen) perovskite nanocrystals (NCs) remains a long-standing challenge due to the lack of a fundamental understanding of how to rationally suppress the formation of structural defects that significantly influence the radiative carrier recombination processes. Here, we develop a theory-guided, general synthetic concept for highly luminescent CsSnX3 NCs. Guided by density functional theory calculations and molecular dynamics simulations, we predict that, although there is an opposing trend in the chemical potential-dependent formation energies of various defects, highly luminescent CsSnI3 NCs with narrow emission could be obtained through decreasing the density of tin vacancies. We then develop a colloidal synthesis strategy that allows for rational fine-tuning of the reactant ratio in a wide range but still leads to the formation of CsSnI3 NCs. By judiciously adopting a tin-rich reaction condition, we obtain narrow-band-emissive CsSnI3 NCs with a record emission quantum yield of 18.4%, which is over 50 times larger than those previously reported. Systematic surface-state characterizations reveal that these NCs possess a Cs/I-lean surface and are capped with a low density of organic ligands, making them an excellent candidate for optoelectronic devices without any postsynthesis ligand management. We showcase the generalizability of our concept by further demonstrating the synthesis of highly luminescent CsSnI2.5Br0.5 and CsSnI2.25Br0.75 NCs. Our findings not only highlight the value of computation in guiding the synthesis of high-quality colloidal perovskite NCs but also could stimulate intense efforts on tin-based perovskite NCs and accelerate their potential applications in a range of high-performance optoelectronic devices.

Experimental Details Synthesis of samples Synthesis of the organically-terminated silicon nanocrystals: A 2 mL of 1-octene was treated with sodium sulfate, and was then collected into Schlenk flask. Next, the Schlenk flask was subjected to freeze-pump-thaw (FPT) cycle on a grease-free vacuum line for at least 30 min by the use of Dewar flasks filled with liquid nitrogen in order to remove the dissolved oxygen. Finally, the oxygen-free 1-octene was stored under argon atmosphere until before use. These procedures were performed on a grease-free glass vacuum line at room temperature and atmospheric pressure. A hydrogen-terminated wafer of silicon was placed in the quartz cell, and purged several times with Ar gas. Next, the quartz cell was filled with the oxygen-free 1-octene for subsequent laser ablation in liquid environment. In the cell, the target silicon was ablated for 30 min by Nd:YAG pulsed laser (λ: 532 nm, power

Functional near-IR (NIR) emitting nanoparticles (NPs) adapted for two-photon excitation fluorescence cell imaging were obtained starting from octadecyl-terminated silicon nanocrystals (ncSi-OD) of narrow photoluminescence (PL) spectra having no long emission tails, continuously tunable over the 700-1000 nm window, PL quantum yields exceeding 30%, and PL lifetimes of 300 μs or longer. These NPs, consisting of a Pluronic F127 shell and a core made up of assembled ncSi-OD kept apart by an octadecyl (OD) layer, were readily internalized into the cytosol, but not the nucleus, of NIH3T3 cells and were non-toxic. Asymmetrical field-flow fractionation (AF4) analysis was carried out to determine the size of the NPs in water. HiLyte Fluor 750 amine was linked via an amide link to NPs prepared with Pluronic-F127-COOH, as a first demonstration of functional NIR-emitting water dispersible ncSi-based nanoparticles.

This paper proposes a novel methodology to synthesize highly fluorescent gold nanoparticles (NPs) with a maximum quantum yield of 16%, in the near-infrared (IR) region. This work discusses the results of using our (previously developed) matrix sputtering method to introduce mercaptan molecules, α-thioglycerol, inside the vacuum sputtering chamber, during the synthesis of metal NPs. The evaporation of α-thioglycerol inside the chamber enables to coordinate to the "nucleation stage" very small gold nanoclusters in the gas phase, thus retaining their photophysical characteristics. As observed through transmission electron microscopy, the size of the Au NPs obtained with the addition of α-thioglycerol varied from approximately 2-3 nm to approximately 5 nm. Plasmon absorption varied with the size of the resultant nanoparticles. Thus, plasmon absorption was observed at 2.4 eV in the larger NPs. However, it was not observed, and instead a new peak was found at approximately 3.4 eV, in the smaller NPs that resulted from the introduction of α-thioglycerol. The Au NPs stabilized by the α-thioglycerol fluoresced at approximately 1.8 eV, and the maximum wavelength shifted toward the red, in accordance with the size of the NPs. A maximum fluorescent quantum yield of 16% was realized under the optimum conditions, and this value is extremely high compared to values previously reported on gold NPs and clusters (generally ∼1%). To our knowledge, however, Au NPs of size>2 nm usually do not show strong fluorescence. By comparison with results reported in previous literature, it was concluded that these highly fluorescent Au NPs consist of gold-mercaptan complexes. The novel method presented in this paper therefore opens a new door for the effective control of size, photophysical characteristics, and structure of metal NPs. It is hoped that this research contributes significantly to the science in this field.

Silicon quantum dots that emit light in the wavelength range of 300 to 450 nm are fabricated. Size‐tunable UV luminescence is achieved by precise control of the diameter of the nanocrystals and complete surface passivation with alkoxy monolayers.

The optical use of colloidal silicon nanocrystals (Si NCs) has gained increasing attention for its possible contributions to building a sustainable society that ideally uses resources and energy with high efficiency without causing damage to the environment or human health. Si wafers (E(g) ≈ 1.1 eV) dominate modern microelectronics as an impressive electronic material, but they exhibit relatively poor optical performance owing to an indirect bandgap structure. Interestingly, however, full control of the size distribution and surface chemistry of the NCs yields size-dependent light emission in a very wide range from near-ultraviolet through visible to near-infrared wavelengths. In addition to such unique luminescence properties, Si exhibits a high chemical affinity to covalent linkages with carbon, oxygen, and nitrogen, thereby producing almost unlimited variations in organic-Si NCs architectures hybridized at the molecular level. To achieve this goal, I note some parameters, including interfacial chemistry, that are emerging as important elements for increasing our understanding of the effect of quantum confinement in nanostructured Si and for realizing efficient fluorescence emission. This article covers new aspects of derivatives of Si NCs in applications that utilize their optical absorption and emission features.