Growth of silver nanoparticles by the citrate reduction of silver nitrate under the range of pH from 5.7 to 11.1 was investigated systematically and quantitatively. Reduction of the silver precursor (Ag + ) was promoted with increased pH, attributed to the higher activity of the citrate reductant under high pH value. Under high pH, the product was composed of both spherical and rod-like silver nanoparticles as a result of the fast reduction rate of the precursor. Under low pH, the product was mainly dominated by triangle or polygon silver nanoparticles due to the slow reduction rate of the precursor. The product that is dominated by spherical silver nanoparticles cannot be acquired by the one-step citrate reduction method in the range of pH investigated, indicating the poor balance between the nucleation and growth processes in the reactions. On the basis of the results of quantitative analyses, a stepwise reduction method, in which the nucleation and growth processes were carried out at high and low pH, respectively, was proposed for the syntheses of spherical silver nanoparticles.

Organic nanoparticles of 1,3-diphenyl-5-(2-anthryl)-2- pyrazoline (DAP) ranging in average diameters from 40 to 160 nm were prepared through the reprecipitation method. The average diameters of the particles were controlled by variation of the aging time. We found that DAP nanoparticles exhibit the size-dependent optical properties. The absorption transitions of the nanoparticles at the lower-energy side experience a bathochromic shift with an increase in the particle size as a result of the increased intermolecular interactions, while the higher-energy bands of anthracene split possibly due to the electronic coupling between the pyrazoline ring of one molecule and the anthracene moiety of the neighboring molecule. Most interestingly, the nanoparticle emission in the blue light region from pyrazoline chromophore shifts to shorter wavelengths with an increase in the particle size, accompanied with a relatively gradual dominance of the emission at about 540 nm from an exciplex between the pyrazoline ring of one molecule and the anthracene moiety of the neighboring molecule. The hypsochromic shift in the emission of DAP nanoparticles was identified as originating from the pronounced decrease in the Stokes shift due to the restraint of vibronic relaxation and the configuration reorganization induced by the increased intermolecular interaction.

On page 83, the page number of Reference [1d] is wrong. The correct number of this reference is given below:

Recently, organic nanoparticles (NPs) have inspired growing research efforts due to the great diversity of organic molecules available, the flexibility in materials synthesis and preparation of NPs, in addition to their size-dependent optical properties.[1] Our group has prepared organic NPs from a series of pyrazoline compounds, which have been widely used as optical brightening agents for textiles and paper and as the hole-conducting medium in photoconductive materials and electroluminescent (EL) devices. It has been shown that the emissions of these pyrazoline derivatives can be tuned by changing the size of the NPs.[2] Such tunable emission is attributed to increased intermolecular interactions with increasing particle size. Here, we show that the emission of organic NPs can also be tuned by employing a doping technique. Doping techniques based on energy transfer have been proven to be an effective way to improve the luminescence efficiency and tune the emission color of EL materials [3] and are widely used in the fabrication of thin-film EL devices.[4]However, little attention has been paid to doped organic NPs, which may potentially serve as promising candidates for advanced optoelectronic materials.[5] Herein, we extend our research interests to doped organic NPs: 1,3,5-triphenyl-2-pyrazoline (TPP) NPs doped with 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM, a redlight-emission material widely used in EL devices) were prepared by the simple reprecipitation method. [6] The absorption spectrum of DCM shows good overlap with the fluorescence emission spectrum of TPP in the 400±550 nm wavelength range (Fig. 1), which is essential for the occurrence of energy transfer in the doping systems. The as-prepared doped NPs present tunable fluorescence emission, dependent on the DCM content, as well as efficient energy transfer. All the NPs, including pure and doped ones, were prepared through the reprecipitation method; mixtures of TPP and DCM in ethanol were used in the preparation of doped NPs. Sizes and shapes of the as-prepared NPs were observed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Representative images of the TPP NPs with a DCM doping level of 10 % (molar) are presented in Figure 2. The NPs are approximately spherical with a mean size of about 30±40 nm. The electron diffraction patterns and X-ray diffraction (XRD) measure-COMMUNICATIONS

Nearly monodispersed spherical silver nanoparticles (Ag NPs) were synthesized by using tannic acid (TA) as both reductant and stabilizer in a 30 °C water bath. The size of the as-prepared Ag NPs could be tuned in a range of 7-66 nm by changing the molar ratio of TA to silver nitrate and pH of the reaction solutions. UV-vis spectra, TEM observations, and temporal evolution of the monomer concentrations for the reactions carried out at different experimental conditions showed that the improved size distribution and size tunability of the Ag NPs were mainly attributed to the use of TA, which could promote the balance of nucleation and growth processes of the NPs effectively. The size of the Ag NPs was extendable up to 200 nm in one-pot fashion by the multi-injection approach. The size-dependent surface-enhanced Raman scattering (SERS) activity of the as-prepared Ag NPs was evaluated, and the NPs with size around 100 nm were identified to show a maximum enhanced factor of 3.6 × 10(5). Moreover, the as-prepared TA-coated Ag NPs presented excellent colloidal stability compared to the conventional citrate-coated ones.

A new self-assembled and highly oriented one-dimensional single-crystal nanostructure of WO3 with hexagonal form was successfully prepared by a mild, solution-based colloidal approach.

Single-phase “greener” phosphor with broadband emission made of colloidal quantum dots (QDs) is most desirable for use as color convertors in white light-emitting diodes (WLEDs). Here, we demonstrate a single “cadmium-free” component system consisting of Cu-doped InP core/ZnS barrier/InP quantum well/ZnS shell QDs, which exhibits two emission peaks by controlling the barrier thickness under single-excitation wavelength, one of which being attributed to Cu-doped InP, and the other resulting from InP quantum well. The dual emissive peaks were successfully tuned in a range from visible to near-infrared by simple control of the core size and the well thickness, respectively. Using optimal structures as color converters, we successfully obtained WLED with a color rending index (CRI) up to 91 and CIE color coordinates of (0.338, 0.330) by combination with blue LED chip, indicating this single-phase phosphor with great promise for use in solid-state lighting due to flexibly tunable dual emission peak position in the entire visible region.

We have used a scalable and inexpensive method to prepare a catalyst comprising graphdiyne nanosheet-supported cobalt nanoparticles wrapped by N-doped carbon (CoNC/GD); this unprecedentedly durable electrocatalyst mediated the hydrogen evolution reaction (HER) with highly catalytic activity over all values of pH. The durability of the CoNC/GD structure was evidenced by the catalytic performance being preserved over 36 000, 38 000, and 9000 cycles under basic, acidic, and neutral conditions, respectively-behavior superior to that of commercial Pt/C (10 wt %) under respective conditions. Such long-term durability has rarely been reported previously for HER catalysts. In addition, this electrode displayed excellent catalytic activity because the improved physical/chemical properties facilitated electron transfer in the composite. The combination of high durability and high activity at all values of pH for this nonprecious metal catalyst suggests great suitability for practical water splitting.