Bandgap Tuning of Silicon Quantum Dots by Surface Functionalization with Conjugated Organic Groups.

The quantum confinement and enhanced optical properties of silicon quantum dots (SiQDs) make them attractive as an inexpensive and nontoxic material for a variety of applications such as light emitting technologies (lighting, displays, sensors) and photovoltaics. However, experimental demonstration of these properties and practical application into optoelectronic devices have been limited as SiQDs are generally passivated with covalently bound insulating alkyl chains that limit charge transport. In this work, we show that strategically designed triphenylamine-based surface ligands covalently bonded to the SiQD surface using conjugated vinyl connectivity results in a 70 nm red-shifted photoluminescence relative to their decyl-capped control counterparts. This suggests that electron density from the SiQD is delocalized into the surface ligands to effectively create a larger hybrid QD with possible macroscopic charge transport properties.

Induction of Strong Long-Lived Room-Temperature Phosphorescence of N-Phenyl-2-naphthylamine Molecules by Confinement in a Crystalline Dibromobiphenyl Matrix.

The design and preparation of metal-free organic materials that exhibit room-temperature phosphorescence (RTP) is a very attractive topic owing to potential applications in organic optoelectronic devices. Herein, we present a facile approach to efficient and long-lived organic RTP involving the doping of N-phenylnaphthalen-2-amine (PNA) or its derivatives into a crystalline 4,4'-dibromobiphenyl (DBBP) matrix. The resulting materials showed strong and persistent RTP emission with a quantum efficiency of approximately 20 % and a lifetime of a few to more than 100 milliseconds. Bright white dual emission containing blue fluorescence and yellowish-green RTP from the PNA-doped DBBP crystals was also confirmed by Commission Internationale de l'Eclairage (CIE) coordinates of (x=0.29-0.31, y=0.38-0.41).

Tailoring the optical gap of silicon quantum dots without changing their size.

The absorption of photons through the direct generation of spatially separated excitons at dot-ligand interfaces is proposed as a promising strategy for tailoring the optical gap of small silicon quantum dots independent of their size. This removes a primary drawback for the use of very small dots in broad range of applications. For instance, the strategy can be applied to solar energy technologies to align the absorption of such dots with the peak of the solar spectrum. The key is to establish both a Type-II energy level alignment and a strong electronic coupling between the dot and ligand. Our first principles analysis indicates that connecting conjugated organic ligands to silicon quantum dots using vinyl connectivity can satisfy both requirements. For a prototype assembly of 2.6 nm dots, we predict that triphenylamine termination will result in a 0.47 eV redshift along with an enhanced near-edge absorption character. Robustness analyses of the influence of oxidation on absorption and of extra alkyl ligands reveal that the control of both factors is important in practical applications.

Ultrathin Freestanding Nanocellulose Film Prepared from TEMPO-Mediated Oxidation and Homogenized Hydrogel.

This paper presents a versatile method to fabricate ultrathin nanofibrillated cellulose (NFC) films as thin as 800 nm by blade coating, which is compatible with a roll-to-roll process on a large scale. Our approach allows obtaining a dried nanocellulose film within a span of 1 h subsequent to 2,2,6,6-tetramethylpiperidine-1-oxyl radical-assisted oxidation and homogenization procedures. One of the thinnest freestanding NFC films with a thickness of 800 nm is achieved using a blade coating of nanocellulose after 72 h of oxidation followed by homogenization with a channel size of 65 µm. Incorporating water-soluble CdTe core-type quantum dots into the nanocellulose film led to a uniform emission under 385 nm UV irradiation, indicating excellent material compatibility. We anticipate nanocellulose developed in our study to be beneficial in biomimicry flying objects, environmentally friendly encapsulation, color filters, and energy storage device membranes, to name a few.

Quinoacridine derivatives with one-dimensional aggregation-induced red emission property.

A new series of acceptor-donor-acceptor (A-D-A) type quinoacridine derivatives (1-3) with aggregation-induced red emission properties were designed and synthesized. In these compounds, the electron-withdrawing 2-(3,5-bis(trifluoromethyl)phenyl)acetonitrile groups act as electron-accepting units, while the alkyl-substituted conjugated core acts as electron-donating units. The restriction of intramolecular rotation was responsible for the AIE behavior of compounds 1-3. All compounds were employed as building blocks to fabricate one-dimensional (1-D) organic luminescent nano- or microwires based on reprecipitation or slow evaporation approaches. Morphological transition from zero-dimensional (0-D) hollow nanospheres to 1-D nanotubes has been observed by recording SEM and TEM images of aggregated sates of compound 2 in THF/H(2)O mixtures at different aging time. It was demonstrated that the synthesized compounds with different lengths of alkyl chains displayed different wire formation properties. The single-crystal X-ray analysis of compound 2 provided reasonable explanation for the formation of 1-D nano- or microstructures.

An "all-in-one" strategy based on the organic molecule DCN-4CQA for effective NIR-fluorescence-imaging-guided dual phototherapy.

Dual phototherapy combining photodynamic therapy (PDT) and photothermal therapy (PTT) is considered to be a more effective therapeutic method against cancer than single treatment. Therefore, the development of a single material with both near-infrared (NIR)-laser-triggered PDT and PTT abilities is highly desirable but remains a great challenge. A design philosophy for photosensitizers for integrated PDT and PTT treatment has been put forward: (1) a high molar extinction coefficient in the NIR region; (2) suitable LUMO and T1 energy levels to regulate intersystem crossing for effective singlet oxygen (1O2) generation for PDT; and (3) the suppression of fluorescence emission to enhance the process of nonradiative transition with appropriate chemical modifications. Herein, an "all-in-one" functional material, di-cyan substituted 5,12-dibutylquinacridone (DCN-4CQA), for diagnosis and therapy was obtained. DCN-4CQA possesses dual-functional phototherapeutic activity and NIR fluorescence and it was produced via a facile synthesis process from the classic organic photoelectric material quinacridone. We then prepared smart water-soluble nanoparticles (NPs), DCN-4CQA/F127, using Pluronic® 127 (F127) as a drug carrier. The NPs exhibited excellent biocompatibility, robust photostability, NIR fluorescence, a high photothermal conversion efficiency (η = 47.3%), and sufficient 1O2 generation (ΦΔ = 24.3%) under NIR laser irradiation. Remarkably, the DCN-4CQA/F127 NPs significantly inhibited tumor growth in mice subjected to NIR laser irradiation. This study provides a new route for the development of highly efficient, low-cytotoxicity photosensitizers for fluorescence-imaging-guided PTT/PDT.

Hydrogen-bonded dimer stacking induced emission of aminobenzoic acid compounds.

A series of aminobenzoic acid crystals with stacking-induced emission properties has been achieved and the packing structures of the hydrogen-bonded acid dimers provided an explanation for the emission characteristics of the crystals.

Mixed anionic surfactant-templated mesoporous silica nanoparticles for fluorescence detection of Fe(3.).

This work demonstrates a novel method for the synthesis of large pore mesoporous silica nanoparticles (MSNs) with a pore diameter of 10.3 nm and a particle diameter of ∼50 nm based on the incorporation of mixed anionic surfactants sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulphate (SDS) as the template in the synthesis process. The dispersity, morphology, pore structure and size of mesoporous nanoparticles were adjusted by changing the molar ratio of two anionic surfactants, the concentration of the co-structure-directing agent (3-aminopropyltrimethoxysilane) and the reaction temperature. The results of synthesis experiments suggested that the formation of large pore MSNs involved a nucleation and growth process. MSNs were post-grafted with a Schiff base moiety for fluorescence sensing of Fe(3+) in water. The applicability of functionalized MSNs was demonstrated by selective fluorescence detection of Fe(3+) in aqueous media.

Recent developments and directions in printed nanomaterials.

In this review, we survey several recent developments in printing of nanomaterials for contacts, transistors, sensors of various kinds, light-emitting diodes, solar cells, memory devices, and bone and organ implants. The commonly used nanomaterials are classified according to whether they are conductive, semiconducting/insulating or biological in nature. While many printing processes are covered, special attention is paid to inkjet printing and roll-to-roll printing in light of their complexity and popularity. In conclusion, we present our view of the future development of this field.

Silica cross-linked nanoparticles encapsulating a phenothiazine-derived Schiff base for selective detection of Fe(iii) in aqueous media.

This work demonstrates a luminescent chemosensor based on silica cross-linked micellar nanoparticles (SCMNPs) designed by encapsulating a phenothiazine-derived Schiff base, (4E)-4-((10-dodecyl-10H-phenothiazin-7-yl)methyleneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (EDDP), for the selective detection of Fe3+. The encapsulation of EDDP inside SCMNPs (EDDP-SCMNPs) can avoid the metal (Fe3+/Fe2+)-promoted hydrolysis of EDDP and, thus, exhibit highly selective determination of Fe3+. The electron transfer (ET) from EDDP in the core to Fe3+ adsorbed on the shell of EDDP-SCMNPs was verified using UV-vis absorption, fluorescent emission and 3D fluorescence spectra. Moreover, EDDP-SCMNPs showed no sensing ability of Fe2+ due to the weak electron-accepting ability of Fe2+. Significantly, because of their ultrasmall size, nontoxicity, good water solubility and biocompatibility, EDDP-SCMNPs have potential applications in biological systems.

Silica cross-linked nanoparticles encapsulating fluorescent conjugated dyes for energy transfer-based white light emission and porphyrin sensing.

This work demonstrated that water-soluble fluorescent hybrid materials can be successfully synthesized by use of silica cross-linked micellar nanoparticles (SCMNPs) as scaffolds to encapsulate fluorescent conjugated dyes for pH sensing, porphyrin sensing and tunable colour emission. Three dyes were separately encapsulated inside SCMNPs (short to dye-SCMNPs). Each of the dye-SCMNPs indicated longer lifetime in water than that of free dye dissolved in organic solvent. The 7-(hexadecyloxy) coumarin-3-ethylformate (HCE) encapsulated inside SCMNPs (HCE-SCMNPs) exhibited fluorescence quenching by pH change in aqueous media. Furthermore, it was confirmed that the radiative and nonradiative energy transfer processes both occurred between HCE-SCMNPs and tetraphenyl-porphyrin (TPP), which were used to synthesize the water-soluble TPP sensor. Significantly, HCE-SCMNPs doped with 5,12-dicotyl-quinacridone (8CQA) and TPP showed water-soluble white light emission (CIE (0.29, 0.34)) upon singlet excitation of 376 nm due to colour adjustment of 8CQA and energy transfer from HCE (donor) to TPP (acceptor).

Reversible piezo- and photochromic behaviors accompanied by emission color switching of two anthracene-containing organic molecules.

Crystalline samples of 3(5)-(9-anthryl)pyrazole and its one derivative exhibit interesting piezochromic behaviors with the emission colors differently changing from blue to green and from green to blue, respectively, upon grinding.