Time-dependent density-functional theory in the projector augmented-wave method

We present the implementation of the time-dependent density-functional theory both in linear-response and in time-propagation formalisms using the projector augmented-wave method in real-space grids. The two technically very different methods are compared in the linear-response regime where we found perfect agreement in the calculated photoabsorption spectra. We discuss the strengths and weaknesses of the two methods as well as their convergence properties. We demonstrate different applications of the methods by calculating excitation energies and excited state Born-Oppenheimer potential surfaces for a set of atoms and molecules with the linear-response method and by calculating nonlinear emission spectra using the time-propagation method.     

Polymer-Metal Nanoparticle Complexes for Improving the Performance of Liquid Crystal Displays

Summary: Here we applied metal nanoparticles as a dopant of liquid crystals. Since liquid crystal molecules are self-assembled, it is not so easy to disperse metal nanoparticles in liquid crystal media. We first prepared metal nanoparticles protected by liquid crystal molecules by reduction of metal ions in the presence of liquid crystal molecules. This liquid crystal molecule-protected metal nanoparticles can be easily dispersed in liquid crystal media to fabricate liquid crystal sol containing metal nanoparticles. A simple liquid crystal molecule, 4′-pentylbiphenyl-4-carbonitrile (abbreviated as 5CB) was used in the present experiments at first. 5CB sol containing metal nanoparticles could construct novel twisted nematic liquid crystal devices (TN-LCDs), which revealed the electrooptic properties depending on the kind of metal of nanoparticles. During the experiments we discovered that 5CB-protected metal nanoparticles could move in liquid crystal media by applying the voltage. This phenomenon is inconvenient for liquid crystal displays, especially those driven by a matrix of thin-film transistors (TFTs). In order to avoid this phenomenon, we prepared polymer-protected metal nanoparticles and applied them to liquid crystal devices, which provided good performance as the devices, i.e., low driving voltage, rapid response at low temperature, and so on.     

Synthesis of Metallic Nanoparticles Using Closed‐Shell Structures as Templates

The synthesis and study of metallic nanoparticles are of continued and significant interest, with applications in materials science, catalysis, and medicine. The properties of metallic nanoparticles depend strongly on their particle size, shape, and interparticle distances. It is therefore desirable for the synthesis of metallic nanoparticles to be controlled for specific shapes and sizes. The rapid development in this research area has attracted intense interest from researchers with diverse expertise, and numerous methods towards the synthesis of monodisperse nanoparticles have been reported. In this Focus Review, we provide an overview of recent progress in the development of the template synthesis of metallic nanoparticles using closed‐shell structures, including biological molecules/assemblies and cage molecules.     

Chitosan nanoparticles: a promising system in novel drug delivery

The ability of nanoparticles to manipulate the molecules and their structures has revolutionized the conventional drug delivery system. The chitosan nanoparticles, because of their biodegradability, biocompatibility, better stability, low toxicity, simple and mild preparation methods, offer a valuable tool to novel drug delivery systems in the present scenario. Besides ionotropic gelation method, other methods such as microemulsion method, emulsification solvent diffusion method, polyelectrolyte complex method, emulsification cross-linking method, complex coacervation method and solvent evaporation method are also in use. The chitosan nanoparticles have also been reported to have key applications in parentral drug delivery, per-oral administration of drugs, in non-viral gene delivery, in vaccine delivery, in ocular drug delivery, in electrodeposition, in brain targeting drug delivery, in stability improvement, in mucosal drug delivery in controlled drug delivery of drugs, in tissue engineering and in the effective delivery of insulin. The present review describes origin and properties of chitosan and its nanoparticles along with the different methods of its preparation and the various areas of novel drug delivery where it has got its application.     

Resonant photoconductance of molecular junctions formed in gold nanoparticle arrays

We investigate the photoconductance properties of oligo(phenylene vinylene) (OPV) molecules in metal-molecule-metal junctions. The molecules are electrically contacted in a two-dimensional array of gold nanoparticles. The nanoparticles in such an array are separated by only few nanometers. This allows to bridge the distance between the nanoparticles with molecules considered as molecular wires such as OPV. We report on the photoconductance of electrically contacted OPV upon resonant optical excitation of the molecules. This resonant photoconductance is sublinear in laser intensity, which suggests that trap state dynamics of the optically excited charge carriers dominate the optoelectronic response.     

Size effect on the fluorescence properties of dansyl-doped silica nanoparticles

We present here the study of the photophysical properties of new dye-doped silica nanoparticles (DDNs) bearing dansyl fluorescent derivatives covalently linked to the silica matrix. The described experimental evidences show how the different location of the chromophores induces great changes in their photophysical behavior, suggesting that fluorophores located near the surface of the nanoparticles have a very different behavior with respect to the internal molecules. These latter ones, in fact, are shielded from the solvent and have a strong blue emission, while those at the periphery interact with the solvent and show a weaker red-shifted emission. As a consequence, the fluorescence properties of these nanoparticles are an average between the characteristics of the two different families of dyes. The relative amount of fluorophores located in the two compartments can be controlled simply by changing the size since, from our results, the thickness of the solvent permeable layer is not relevantly affected by the diameter of the nanoparticles. It is noteworthy that the fluorophores located in the outer shell exhibit very peculiar features: they are sensitive and interact with small molecules such as solvent molecules but, at the same time, they are not accessible to big receptor species such as beta-cyclodextrins. Such results indicate that most of the solvent-sensitive dansyl moieties are located within pores large enough to only accommodate solvent but not big molecules as cyclodextrins, giving precious insight on the morphology of the nanoparticles.     

Long-Term Colloidally Stable Aqueous Dispersions of ≤5 nm Spinel Ferrite Nanoparticles

Applications in biomedicine and ferrofluids, for instance, require long-term colloidally stable, concentrated aqueous dispersions of magnetic, biocompatible nanoparticles. Iron oxide and related spinel ferrite nanoparticles stabilized with organic molecules allow fine-tuning of magnetic properties via cation substitution and water-dispersibility. Here, we synthesize≤5 nm iron oxide and spinel ferrite nanoparticles, capped with citrate, betaine and phosphocholine, in a one-pot strategy. We present a robust approach combining elemental (CHN) and thermal gravimetric analysis (TGA) to quantify the ratio of residual solvent molecules and organic stabilizers on the particle surface, being of particular accuracy for ligands with heteroatoms compared to the solvent. SAXS experiments demonstrate the long-term colloidal stability of our aqueous iron oxide and spinel ferrite nanoparticle dispersions for at least 3 months. By the use of SAXS we approved directly the colloidal stability of the nanoparticle dispersions for high concentrations up to 100 g L⁻¹.     

电泳技术在纳米颗粒分离中的应用

合成纳米颗粒常在尺寸和形状方面具有广泛分布.在很多实验中,需要利用一定大小及形状的纳米颗粒的独特物理化学性质,因此,简便快速的纳米颗粒分离技术越来越受到诸多科学领域的重视.电泳技术以其高分辨率,被广泛用于多种生物大分子如核酸、蛋白质等的分离纯化.纳米颗粒在尺寸上与生物体中的蛋白复合物、细胞器和微生物等十分接近,考虑到带电纳米颗粒与生物分子在电场中的运动行为的相似性,运用电泳技术进行纳米颗粒的鉴定、分离和纯化是一种新的思路,并取得了良好的实验结果.本文主要介绍了琼脂糖凝胶电泳、毛细管电泳以及其他一些电泳技术在纳米颗粒分离中的研究进展.     

Bright photoluminescent hybrid mesostructured silica nanoparticles

Bright photoluminescent mesostructured silica nanoparticles were synthesized by the incorporation of fluorescent cyanine dyes into the channels of MCM-41 mesoporous silica. Cyanine molecules were introduced into MCM-41 nanoparticles by physical adsorption and covalent grafting. Several photoluminescent nanoparticles with different organic loadings have been synthesized and characterized by X-ray powder diffraction, high resolution transmission electron microscopy and nitrogen physisorption porosimetry. A detailed photoluminescence study with the analysis of fluorescence lifetimes was carried out to elucidate the cyanine molecules distribution within the pores of MCM-41 nanoparticles and the influence of the encapsulation on the photoemission properties of the guests. The results show that highly stable photoluminescent hybrid materials with interesting potential applications as photoluminescent probes for diagnostics and imaging can be prepared by both methods.     

Effects of silver nanoparticles doping on morphology and luminescence behaviour of ferroelectric liquid crystals Langmuir–Blodgett films

We report the deposition of Langmuir–Blodgett (LB) thin films of low-weight dispersed composite systems of ferroelectric liquid crystals (FLCs)–functionalised silver (Ag) nanoparticles. Because of their amphiphilic nature the molecules form stable Langmuir monolayers, which were transferred to silicon substrates. We noticed that absorption wave numbers are present for each bond constituting FLC–nanoparticles composite system, ensuring a complete transfer of molecules from water sub-phase. XRD showed intense peaks at 2θ = 3.2° due to the layer structure of FLC molecules. We infer from the morphology of LB films that doping of nanoparticles do not provide any hindrance to SmC* layer structure of FLC molecules. The photoluminescence study indicates blue shift in emission spectra and peak intensity increases with Ag nanoparticles concentration.     

Cubic liquid-crystalline nanoparticles

Cubic liquid-crystalline nanoparticles prepared from aqueous dispersions of cubic lipid-water phases are kinetically stable in the presence of certain dispersing agents. The properties of cubic nanoparticles from monoolein-water and other lipid-water systems have been examined with a variety of experimental techniques. The cubic nanoparticles can be stabilized by polymerization of the reactive lipids in cubic lipid assemblies. Several low-energy-input methods have been developed to facilitate the production and application of cubic nanoparticles. The ability to incorporate and deliver lipophilic, amphiphilic, and water-soluble molecules in a controlled manner and the good biocompatibility of cubic nanoparticles make them excellent candidates for drug-delivery applications.     

Gold nanoparticles for the development of clinical diagnosis methods

The impact of advances in nanotechnology is particularly relevant in biodiagnostics, where nanoparticle-based assays have been developed for specific detection of bioanalytes of clinical interest. Gold nanoparticles show easily tuned physical properties, including unique optical properties, robustness, and high surface areas, making them ideal candidates for developing biomarker platforms. Modulation of these physicochemical properties can be easily achieved by adequate synthetic strategies and give gold nanoparticles advantages over conventional detection methods currently used in clinical diagnostics. The surface of gold nanoparticles can be tailored by ligand functionalization to selectively bind biomarkers. Thiol-linking of DNA and chemical functionalization of gold nanoparticles for specific protein/antibody binding are the most common approaches. Simple and inexpensive methods based on these bio-nanoprobes were initially applied for detection of specific DNA sequences and are presently being expanded to clinical diagnosis. Figure Colorimetric DNA/RNA detection using salt induced aggregation of AuNP-DNA nanoprobes.     

Microbial synthesis of gold nanoparticles: Current status and future prospects

Gold nanoparticles have been employed in biomedicine since the last decade because of their unique optical, electrical and photothermal properties. Present review discusses the microbial synthesis, properties and biomedical applications of gold nanoparticles. Different microbial synthesis strategies used so far for obtaining better yield and stability have been described. It also includes different methods used for the characterization and analysis of gold nanoparticles, viz. UV–visible spectroscopy, Fourier transform infrared spectroscopy, X ray diffraction spectroscopy, scanning electron microscopy, ransmission electron microscopy, atomic force microscopy, electron dispersive X ray, X ray photoelectron spectroscopy and cyclic voltametry. The different mechanisms involved in microbial synthesis of gold nanoparticles have been discussed. The information related to applications of microbially synthesized gold nanoparticles and patents on microbial synthesis of gold nanoparticles has been summarized.     

Predicting solid-state heats of formation of newly synthesized polynitrogen materials by using quantum mechanical calculations

We present density functional theory level predictions and analysis of the basic properties of newly synthesized high-nitrogen compounds together with 3,6-bis(2H-tetrazol-5-yl)-1,2,4,5-tetrazine (BTT) and 3,3'-azobis(6-amino-1,2,4,5-tetrazine) (DAAT), for which experimental data are available. The newly synthesized high-nitrogen compounds are based on tricycle fused 1,2,4-triazine and 1,2,4,5-tetrazine heterocycles. In this work, the molecules BTT and DAAT have been studied in order to validate the theoretical approach and to facilitate further progress developments for the molecules of interest. Molecular structural properties are clarified, and IR spectra predictions are provided to help detection of those compounds in the experiment. The energy content of the molecules in the gas phase is evaluated by calculating standard enthalpies of formation, by using a special selection of isodesmic reaction paths. We also include estimates of the condensed-phase heats of formation and heats of sublimation in the framework of the Politzer approach. The obtained properties are consistent with those new high-nitrogen compounds being a promising set of advanced energetic materials.     

单分散介孔氧化硅纳米颗粒的制备及其在生物材料方面的应用

单分散介孔氧化硅纳米颗粒由于其自身的优点,在当前许多领域有着广泛的应用前景。本文综述了近十几年来单分散介孔氧化硅纳米颗粒的制备方法以及在生物材料方面的应用。在制备方法方面,根据其制备机理分为稀溶液法、微乳法、模板剂法以及向反应体系中加入不同的添加剂等方法,制备出分散性好、不同形态、孔径尺寸可调的介孔氧化硅纳米颗粒。在生物材料的应用方面,主要介绍了其在药物与生物活性分子的负载与控制释放、生物大分子的固载与分离、生物标记与临床诊断等方面的应用。     

Emulsion Techniques for the Production of Pharmacological Nanoparticles

Nanoparticles have the advantages over micron‐sized particles to typically provide higher intracellular uptake and drug bioavailability. Emulsion techniques are commonly used methods for producing nanoparticles aiming at high encapsulation efficiency, high stability, and low toxicity. Here, the recent developments of nanoparticles prepared from emulsions, the synthesis of nanoparticles, their physicochemical properties, and their biomedical applications are discussed. Selection of techniques, such as emulsion polymerization, miniemulsion polymerization, microemulsion polymerization, and emulsion‐solvent evaporation processes, strongly influences morphologies, size distributions, and particle properties. Details in the synthetic strategies governing the performance of nanoparticles in bioimaging, biosensing, and drug delivery are presented. Benefits and limitations of molecular imaging techniques are also discussed.     

Colloidal Hybrid Nanostructures: A New Type of Functional Materials

One key goal of nanocrystal research is the development of experimental methods to selectively control the composition and shape of nanocrystals over a wide range of material combinations. The ability to selectively arrange nanosized domains of metallic, semiconducting, and magnetic materials into a single hybrid nanoparticle offers an intriguing route to engineer nanomaterials with multiple functionalities or the enhanced properties of one domain. In this Review, we focus on recent strategies used to create semiconductor–metal hybrid nanoparticles, present the emergent properties of these multicomponent materials, and discuss their potential applicability in different technologies.     

Electrochemical detection and characterization of nanoparticles: A potential tool for environmental purposes

The incorporation of engineered nanoparticles in commercial products and industrial processes has broadly increased in recent years, which raises concerns about their environmental impact. In this review, we present electrochemistry as a promising analytical tool towards the detection and characterization of nanoparticles for environmental purposes. Recent research has not only demonstrated the applicability of electrochemical methods for the quantification of nanoparticles in environmental samples, but also for the study of properties and transformations of nanoparticles. All these aspects are very relevant to understand their toxicity in the environment. In this context, we discuss several electrochemical methods to quantify and study the size and shape, surface properties, interparticle interactions, chemical reactivity and speciation of nanoparticles.