Regenerative synthesis of copper nanoparticles by?photoirradiation

Copper nanoparticles have attracted much attention because of their low cost, and because their use can contribute toward the sustainability of metal resources. In this study, copper nanoparticles were synthesized by the photoirradiation of copper acetate solution at room temperature. The diameter and chemical composition of the obtained copper nanoparticles were analyzed using field-emission scanning electron microscope (FE-SEM) spectrophotometer and an X-ray photoelectron spectrometer. Well-dispersed copper nanoparticles with  ~5 nm in diameter were observed in the solution. On the other hand, when the nanoparticle solution was exposed to fresh air, nanoparticles were not observed in the solution. Furthermore, the copper nanoparticles were recovered from a solution of decomposed nanoparticles by re-photoirradiation.     

Erratum to “Indium doping effect on properties of ZnO nanoparticles synthesized by sol-gel method”

Figure 2 in our original paper [Chin. Phys. B 28 047701(2019)] was downloaded by default. We present the correct figure in this erratum.     

II–VI semiconductor nanoparticles synthesized by laser ablation

Nanoparticles of the II–VI semiconductors CdTe, CdSe and ZnTe were synthesized by laser ablation (387 nm, 180 fs, 1 kHz, pulse energy of 7 μJ (fluence of 2 J/cm²)) of the target materials in methanol, de-ionized water and acetone. The nanoparticles size distributions follow log-normal functions with median diameters between about 6 and 11 nm for the several materials. The nanoparticles have the same crystalline structure as that of the corresponding bulk material and under the present conditions of ablation are rich in the higher volatility element of the two in the binary alloy and oxidized. Photoluminescence emission in the green-yellow (∼570 nm) was detected from CdSe nanoparticles.     

Co–CoO nanoparticles prepared by reactive gas-phase aggregation

The technique of gas-phase aggregation has been used to prepare partially oxidized Co nanoparticles films by allowing a controlled flow of oxygen gas into the aggregation zone. This method differs from those previously reported, that is, the passivation of a beam of preformed particles in a secondary chamber and the conventional (low Ar pressure) reactive sputtering of Co to produce Co–CoO composite films. Transmission electron microscopy shows that the mean size of the particles is about 6 nm. For sufficiently high oxygen pressures, the nanoparticles films become super-paramagnetic at room temperature. X-ray diffraction patterns display reflections corresponding to fcc Co and fcc CoO phases, with an increasing dominance of the latter upon increasing the oxygen pressure in the aggregation zone, which is consistent with the observed reduction in saturation magnetization. The cluster films assembled with particles grown under oxygen in the condensation zone exhibit exchange-bias fields (about 8 kOe at 20 K) systematically higher than those measured for Co–CoO core-shell nanoparticles prepared by oxidizing preformed particles in the deposition chamber, which we attribute, in the light of results from annealing experiments, to a higher ferromagnetic–antiferromagnetic (Co–CoO) interface density.     

Two-photon imaging of lymphoma cells targeted by gold nanoparticles

Gold nanoparticles(NPs)have highly efficient multi-photon-induced luminescence.In this paper,we record the two-photon images of gold NPs,lymphoma cell line Karpas 299,and Karpas 299 incubated with 30-nm-diameter gold NPs and ACT-1 antibody conjugates(Au30-ACT-1 conjugates)by using a multi-photon microscopy system.Due to the specific conjugation of ACT-1 antibody and cell membrane receptor CD25,gold NPs are only bound to the surface of cell membrane of Karpas 299.The luminescence intensity of gold NPs is higher than that of cells at 750-nm laser excitation.By comparing the images of Karpas 299 cells incubated with and without gold NPs,it is found that by means of gold NPs,we can get clear cell images with lower excitation power.Their excellent optical and chemical properties make gold NPs an attractive contrast agent for cellular imaging.     

EXAFS research on Nd2O3 nanoparticles modified by AOT

The Nd2O3 nanoparticles which modified by AOT was prepared using micrioemulsion method in the system of water /xylene.L3 edge XAFS was used to determine the difference of the local structure arund Nd^3 ion and the electrical structure between the nanocystalline Nd2O3 and the coarse bulk microcrystalline Nd2O3.It was found that Nd-O distance increased with the form of nanocrystallite and the intensity of absorption edge also enhanced at the same time.     

Detecting Multi-Scale Coherent Eddy Structures and Intermittency in Turbulent Boundary Layer by Wavelet Analysis

Multi-scale decomposition by wavelet transform has been performed to velocity time sequences obtained by fine measurements of turbulent boundary layer flow. A conditional sampling technique for detecting multi-scale coherent eddy structures in turbulent field is proposed by using multi-scale instantaneous intensity factor and flatness factor of wavelet coefficients. Although the number of coherent eddy structures in the turbulent boundary layer is very small, their energy percentage with respect to the turbulence kinetic energy is high. Especially in buffer layer, the energy percentages of coherent structures are significantly higher than those in the logarithmic layer, indicating that the buffer layer is the most active region in the turbulent boundary layer. These multi-scale coherent eddy structures share some common dynamical characteristics and are responsible for the anomalous scaling law in the turbulent boundary layer.     

Detection of biotin–avidin affinity binding by exploiting a self-referenced system composed of upconverting luminescent nanoparticles and gold nanoparticles

We demonstrate an affinity system based on the interaction of two types of nanoparticles. The first consists of upconverting luminescent NaYF₄:Yb,Er nanoparticles (UCNPs) with a size of 40–100 nm, absorbing light in the infrared and showing luminescence at 521, 543 and at 657 nm. The second consists of (red) gold nanoparticles (Au-NPs) with a size of about 50 nm and capable of absorbing the green luminescence of the UCNPs. By labeling the UCNPs with avidin and the AuNPs with biotin we have established a model system for a self referenced affinity system applicable to sensing in biological samples. In the presence of avidin-modified UCNPs, the biotinylated Au-NPs can be detected in the range from 12 to 250 μg mL⁻¹ by ratioing the intensity of the red (analyte-independent) emission to that of the green (analyte-dependent) emission band. The nanoparticles were characterized in terms of size and composition using transmission electron microscopy, thermogravimetry, and FTIR spectroscopy.     

Magnetite–polylactic acid nanoparticles by surface initiated organocatalysis ring opening polymerization

Fe nanoparticle (NP)-assembled thin films with different thickness were prepared by femtosecond-pulsed laser deposition using different deposition times. The proper selection of the deposition time allows to control, to a certain degree, the morphology and topology of the deposited Fe nanoparticles (NPs) assembly, fostering non-uniform dense assemblies of NPs, with the consequent reduction of the influence of the exchange interactions on the macroscopic magnetic properties with decreasing thickness. The magnetic behavior of the Fe NP-assembled films with decreasing thickness is characterized by higher coercive field (H _c) values (a factor ≈4.5) and a good compromise between the hysteresis loops squareness and moderate exchange interactions, strongly correlated with the NPs topology.     

Acceleration and inhibition of amyloid-β fibril formation by peptide-conjugated fluorescent-maghemite nanoparticles

The formation of amyloid aggregates by association of peptides into ordered structures is hallmark of certain neurodegenerative disorders. Exploring the effect of specific nanoparticles on the formation of amyloid fibrils may contribute toward a mechanistic understanding of the aggregation processes, leading to design nanoparticles that modulate the formation of toxic amyloid plaques. Uniform maghemite (γ-Fe₂O₃) magnetic nanoparticles, containing fluorescein covalently encapsulated within (F-γ-Fe₂O₃)_, were prepared. These F-γ-Fe₂O₃ nanoparticles of 14.0 ± 4.0 nm were then coated with human serum albumin (HSA) via a precipitation process. Covalent conjugation of the spacer arm succinimidyl polyethylene glycol succinimidyl ester (NHS–PEG–NHS) to the F-γ-Fe₂O₃~HSA nanoparticles was then accomplished by interacting the primary amine groups of the HSA coating with excess NHS–PEG–NHS molecules. Covalent conjugation of the peptides amyloid-β 40 (Aβ₄₀) or Leu-Pro-Phe-Phe-Asp (LPFFD) onto the surface of the former fluorescent nanoparticles was then performed, by interacting the terminal activated NHS groups of the PEG derivatized F-γ-Fe₂O₃~HSA nanoparticles with primary amino groups of the peptides. Kinetics of the Aβ₄₀ fibrillation process in the absence and presence of varying concentrations of the Aβ₄₀ or LPFFD conjugated nanoparticles were also elucidated. The non-peptide conjugated fluorescent nanoparticles do not affect the Aβ₄₀ fibrillation process significantly. However, the Aβ₄₀-conjugated nanoparticles (F-γ-Fe₂O₃~HSA–PEG–Aβ₄₀) accelerate the fibrillation process while the LPFFD-conjugated nanoparticles (F-γ-Fe₂O₃~HSA–PEG–LPFFD) inhibit it. By applying MRI and fluorescence imaging techniques simultaneously these bioactive fluorescent magnetic iron oxide nanoparticles can be used as an efficient tool to study and control the Aβ₄₀ amyloid fibril formation process.     

Angular optical characteristics of light scattered by double-layer metal–oxide nanoparticles

The interaction of Tb(III)-2-{[(4-methoxy benzoyl) oxy]} methyl benzoic acid binary complex with nucleosides (adenosine, cytidine, guanosine and inosine) was investigated using UV and fluorescence methods. The reaction of Tb-complex with cytidine, guanosine and adenosine is accompanied by shift to longer wavelength in the absorption band, while there is a blue shift in the absorption band with an enhancement in the molar absorptivity upon the reaction with inosine. The fluorescence intensity of Tb(III)-2-{[(4- methoxy benzoyl) oxy]} methyl benzoic acid binary complex at λ = 545 nm (5D4 → 7F5) was decreased with the addition of the nucleoside molecule following the order: cytidine > inosine > guanosine > adenosine.     

Synthesis and structures of Al–Ti nanoparticles by hydrogen plasma-metal reaction

Three kinds of Al–Ti nanoparticles (7.7, 27.8, and 42.6 at.% Ti) have been prepared from Al–65, Al–85, and Al–88 at.% Ti master alloys by hydrogen plasma-metal reaction, with average particle sizes of 30, 25, and 80 nm, respectively. The higher evaporation rate of Al than Ti resulted in the low Ti contents in the nanoparticles than those in the master alloys. Microscopy observation revealed that the primary nanoparticles are spherical in shape, and occur as chain aggregates of several individual nanoparticles due to the faster collision rate than the coalescence rate. All the Al–Ti nanoparticles contain amorphous alumina layers of about 2–3 nm in thickness surrounding the crystalline core. AlTi intermetallic nanoparticles were successfully produced for Al–27.8 at.% Ti, with a single crystal of AlTi in one chain aggregate. The composite nanoparticles of Al together with some Al₃Ti phases are prepared for Al–7.7 at.% Ti, with each phase in the individual particle of one chain aggregate. The composite nanoparticles of AlTi with some AlTi₃ were produced for Al–42.6 at.% Ti, with each phase in the individual particle of one chain aggregate. The formation mechanism of Al–Ti nanoparticles was interpreted in terms of phase transition and the effect of hydrogen.     

Structural analysis of cobalt titanate nanoparticles obtained by sol–gel process

In this work we report the synthesis of nanocomposites based on nanoparticles of cobalt titanate and titanium dioxide in their anatase crystalline phase by a sol–gel process. The synthesized nanoparticles of titanate vary from 1 to 6 nm in size. They are embedded in the anatase matrix, and they were obtained from TiO₂ monoliths doped with Co²⁺. The formation of cobalt titanate nanoparticles showed a linear dependence on the cobalt concentration. The cobalt titanate nanocrystals are very stable even at temperatures higher than 1000 °C. The crystalline structures of the samples were examined using high-resolution transmission electron microscopy and X-ray diffraction. Molecular simulation methods were utilized for a better understanding and for improving the analytical data interpretation of the experimental results. PACS 61.16.Bg; 79.60.Jv; 61.46.+w; 61.50.Ah     

“Thought-experiments” by molecular dynamics

A method for studying the dynamical properties of liquids by molecular dynamics simulation is described. Its basis is the measurement of the response to a weak applied field of appropriate character. The explicit form of the mechanical perturbation is worked out in several cases, and details are given of the numerical techniques used in implementing the method.     

Encapsulation and controlled release from core–shell nanoparticles fabricated by plasma polymerization

Core–shell nanostructures have been synthesized by plasma deposition in radio-frequency plasma reactor. Silica and KCl nanoparticles were encapsulated by deposition of isopropanol-based films of amorphous hydrogenated carbon. Through control of the deposition time, under constant deposition rate of 1 nm/min, particles are encapsulated in a layer of plasma polymer with thickness between 15 and 100 nm. Films are robust, chemically inert, thermally stable up to 250°C. The permeability of the shells is determined by depositing films of various thickness onto KCl nanoparticles and monitoring the dissolution of the core in aqueous solution. The dissolution profile is characterized by an initial rapid release, followed by a slow release that lasts up to 30 days for the thickest films. The profile is analyzed by Fickian diffusion through a spherical matrix. We find that this model captures very accurately the entire release profile except for the first 12 hours during which, the dissolution rate is higher than that predicted by the model. The overall diffusion coefficient for the dissolution of KCl is 3 × 10⁻²¹ m²/s.     

Preparation of monodispersed Pd nanoparticles by laser ablation at air–suspension interface

Strontium titanate (SrTiO₃) has attracted a lot of attention because of its possible applications in new microelectronic devices. It is a material with a high dielectric constant, low leakage current, and some of its properties can be changed by adding or modifying the concentration of a dopant, which can be used for a wide range of functional purposes, from simple capacitors to complicated microwave devices. Therefore, in this work, we report the development of a new route to synthesize SrTiO₃ nanoparticles based on the solvothermal method by employing two precursor solutions: strontium chloride and titanium(IV) butoxide. Our route allows the production of cubic SrTiO₃ nanoparticles with a narrow size distribution. The particle sizes range between 8 and 24 nm, forming agglomerates of SrTiO₃ in the range of 128–229 nm. It was demonstrated that the Ti/Sr molar ratio employed into the precursor solution has an important effect onto the chemical composition of the resulting SrTiO₃ nanoparticles: when using Ti/Sr < 1, the formation and incorporation of the SrCO₃ compound into the nanoparticles was observed while with Ti/Sr ≥ 1 nanoparticles are free of contaminants. The as-prepared nanoparticles were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, high-resolution TEM, selected area electron diffraction, scanning electron microscopy, and dynamic light scattering.     

Morphology of supported silver nanoparticles characterized by?optical and thermal desorption spectroscopy

Silver nanoparticles grown on a quartz substrate are investigated with optical and thermal desorption spectroscopy (TDS). Detailed information on the nanoparticle morphology is gained with new methods of data analysis. First, fitting the extinction spectra, using a comprehensive model, allows an estimation of the effective particle–particle distance. Second, the total surface area of the particles is determined with TDS of xenon. Third, the dependence of the plasmon resonance position on the amount of adsorbed xenon or benzene is used as a measure of the average particle size. The results for these three parameters, which are critical for potential applications of nanoparticle arrays, are shown to be mutually consistent. The methods demonstrated here are complementary to scanning probe techniques which characterize the particle morphology on a microscopic length scale.     

Three-directional structural characterization of hexagonal packed nanoparticles by hexagonal digital moiré method

We present the hexagonal digital moiré method for three-directional structural characterization of hexagonal packed nanostructures. A mismatch between a three-way grating and a nanoparticle assembly is shown to produce hexagonal moiré fringes due to the interference between three groups of parallel moiré patterns. The measuring principles of the pitches and the orientations of the three 1D arrays of the nanoparticles are presented. The structural information on a silica nanoparticle assembly is analyzed.     

Rapid and efficient synthesis of colloidal gold nanoparticles by?arc discharge method

The microstructural (XRD and SEM) and dielectric behavior of Pb(Zr_0.54Ti_0.46)O₃ (PZT 54/46) ceramic system with donor (La, Nb and La+Nb) doping was studied. For all Nb-doped PZT samples, only one (tetragonal) phase was found, which confirms the compositional shifts near the morphotropic phase boundary. For La- and La+Nb-doped samples, there are two (rhombohedral and tetragonal) phases. Dielectric characteristic behavior (1/ε) for La- and La+Nb-doped PZT was associated with two-phase transitions: Ferro–Ferro at low temperature and Ferro–Para at Curie temperature. For Nb-doped samples, only one phase transition is observed, which indicates the presence of a single ferroelectric phase.