Ultrafast Preparation Research Articles

Ultrafast preparation and detection of ring currents in single atoms

Quantum particles can penetrate potential barriers by tunneling (1). If that barrier is rotating, the tunneling process is modified (2,3). This is typical for electrons in atoms, molecules or solids exposed to strong circularly polarized laser pulses (4,5). Here we measure how the transmission probability through a rotating tunnel depends on the sign of the magnetic quantum number m of the electron and thus on the initial sense of rotation of its quantum phase. We further show that the electron keeps part of that rotary motion on its way through the tunnel by measuring m-dependent modification of the electron emission pattern. These findings are relevant for attosecond metrology as well as for interpretation of strong field electron emission from atoms and molecules (6-13) and directly demonstrates the creation of ring currents in bound states of ions with attosecond precision. In solids, this could open a way to inducing and controlling ring-current related topological phenomena (14).

Facile fabrication of organic dyed polymer nanoparticles with aggregation-induced emission using an ultrasound-assisted multicomponent reaction and their biological imaging

Ultrasound as a powerful technique has increasingly been used in both industry and academia in recent years. Herein, an efficient approach to the ultrafast preparation of cross-linked fluorescent copolymers (PEGMA-AEMA-TPE) with aggregation-induced emission (AIE) via an ultrasound-assisted multicomponent reaction (MCR) is described. A number of characterization techniques were carried out to certify the successful preparation of these AIE-active copolymers. Due to the introduction of a hydrophilic PEG fragment and a hydrophobic AIE-active dye, the obtained fluorescent copolymers showed amphiphilic properties and could assemble into organic dyed polymer nanoparticles (ODPNs) with great water dispersibility. The final PEGMA-AEMA-TPE ODPNs demonstrated intense fluorescence, strong photostability, a low critical micelle concentration (CMC) of 0.007 mg mL−1 and high biocompatibility. More importantly, the PEGMA-AEMA-TPE ODPNs show obvious AIE characteristics, which could elegantly overcome the quenching effect caused by the aggregation of ODPNs based on conventional organic dyes. Considered the above results, we believe that these AIE-active ODPNs should be promising candidates for biological imaging and other biomedical applications.

Ultra-fast preparation of high-performance thermoelectric bulk TiNiSb0.05Sn0.95 by microwave synthesis.

The antimony-doped half-Heusler thermoelectric bulk TiNiSb0.05Sn0.95 was prepared via ultra-fast 4.5 min microwave synthesis, cold-press forming and 20 min microwave pressureless sintering. The electrical properties i.e. the Seebeck coefficient (S), electrical resistivity (ρ), and carrier concentration (n) and mobility (μ) were measured on a Seebeck coefficient/resistance analysis system (S/RAs) and Hall effect measurement system (HEMS), respectively. The thermal conductivity (κ) was measured on a laser flash thermal analyzer (LFA). The results show that a high purity single phase was obtained after microwave sintering. The electrical resistivity is 2.70-5.33 μΩ m at temperatures ranging from ∼300 to 773 K. The highest power factor of 4042 μW m-1 K-2 was achieved at 473 K. The microstructure analyses show that numerous circular intercrystalline pores caused by microwave sintering are present within the TiNiSn grains. The lattice and total thermal conductivity are 1.76-3.77 and 4.66-5.98 W m-1 K-1. The highest thermoelectric figure of merit of 0.44 was achieved at 623 K.

Ultrafast Preparation of Monodisperse Fe3 O4 Nanoparticles by Microwave-Assisted Thermal Decomposition.

Thermal decomposition, as the main synthetic procedure for the synthesis of magnetic nanoparticles (NPs), is facing several problems, such as high reaction temperatures and time consumption. An improved a microwave-assisted thermal decomposition procedure has been developed by which monodisperse Fe3 O4 NPs could be rapidly produced at a low aging temperature with high yield (90.1 %). The as-synthesized NPs show excellent inductive heating and MRI properties in vitro. In contrast, Fe3 O4 NPs synthesized by classical thermal decomposition were obtained in very low yield (20.3 %) with an overall poor quality. It was found for the first time that, besides precursors and solvents, magnetic NPs themselves could be heated by microwave irradiation during the synthetic process. These findings were demonstrated by a series of microwave-heating experiments, Raman spectroscopy and vector-network analysis, indicating that the initially formed magnetic Fe3 O4 particles were able to transform microwave energy into heat directly and, thus, contribute to the nanoparticle growth.

Ultrafast Preparation of Black Phosphorus Quantum Dots for Efficient Humidity Sensing.

Black phosphorus quantum dots (BPQDs) have been prepared by a high turbulent shear rate generated from a household kitchen blender. A layer-by-layer disintegration mechanism of bulk BP crystals is suggested. As-synthesized BPQDs have shown excellent humidity sensing and photothermal converting properties. Importantly, this work not only explores potential applications for the BPQDs but also provides a successful paradigm for preparing the QDs of other layered materials.

Ultrasonication-assisted ultrafast preparation of multiwalled carbon nanotubes/Au/Co3O4 tubular hybrids as superior anode materials for oxygen evolution reaction

Efficient and simple operation electrocatalysts for the oxygen evolution reaction (OER) are essential components of renewable energy technologies. Here, a novel, simple, and efficient routine is presented for the first time by constructing a high-efficiency anode catalyst for OER. With the aid of high intensity ultrasound, a uniformly loading, conductive multiwalled carbon nanotubes/metal/transition metal-oxide (CNTs-Au@Co3O4) tubular hybrids is synthesized. In alkaline media, the materials catalyze OER with an onset potential of 1.56 V vs. reversible hydrogen electrode (RHE) and overpotential only of 350 mV to achieve a stable current density of 10 mA cm−2 for at least 25 h. The unusual catalytic activity and stability is due to the following elements. Firstly, the tubular architecture not only provides sufficient active centers for OER, but also improves rapid mass/charge transport. Secondly, Co3O4 layer protects Au nanoparticles (NPs) against detachment. In addition, we also prove that the highest electronegativity metal Au accelerate the formation of catalytic active sites of CoIV species for OER. It is believed that this simple preparation method paves a way to fabricate a range of CNTs/metal/metal-oxide based composites as superior OER catalysts.

Ultrafast preparation of three-dimensional porous tin–graphene composites with superior lithium ion storage

Three-dimensional porous Sn–graphene composites have been prepared on Ni foam by an easy, binder-free, low-cost and ultrafast electrophoretic deposition method. The structure and morphology of the as-prepared composite material are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, high resolution transmission electron microscopy, field emission scanning electron microscopy and elemental analysis. The lithium storage performance of the three-dimensional porous Sn–graphene anode is evaluated by cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy measurements. Results show that the composite material with a graphene content of 6.1 wt% delivers a reversible capacity of 552 mA h g−1 after 200 cycles at a current density of 500 mA g−1. The synthetic approach presented in this work may provide a facile strategy for the preparation of three-dimensional porous metal–graphene composites.

Ultrafast preparation of branched poly(methyl Acrylate) through single electron transfer living radical polymerization at room temperature

Ultrafast preparation of branched poly(methyl acrylate) (BPMA) with high‐molecular weight through single electron transfer living radical polymerization (SET‐LRP) of inimer at 25°C has been attempted, atom transfer radical polymerization (ATRP) at 60°C was also carried out for comparison. Gas chromatography, proton nuclear magnetic resonance, and triple detection size exclusion chromatography were used to analyze these polymerizations. As expected, SET‐LRP system showed much faster polymerization rate than ATRP system, the calculated apparent propagation rate constants (kpapp) are 3.69 × 10−2 min−1 and 6.23 × 10−3 min−1 for SET‐LRP and ATRP system, respectively. BPMA with high‐molecular weight (Mw.MALLS = 86,400 g mol−1) compared with that in ATRP (Mw.MALLS = 61,400 g mol−1) has been prepared. POLYM. ENG. SCI., 54:1579–1584, 2014. © 2013 Society of Plastics Engineers

A Critical Assessment of the Specific Role of Microwave Irradiation in the Synthesis of ZnO Micro‐ and Nanostructured Materials

A rapid, microwave-assisted hydrothermal method has been developed to access ultrafine ZnO hexagonal microrods of about 3-4 μm in length and 200-300 nm in width by using a 1:5 zinc nitrate/urea precursor system. The size and morphology of these ZnO materials can be influenced by subtle changes in precursor concentration, solvent system, and reaction temperature. Optimized conditions involve the use of a 1:3 water/ethylene glycol solvent system and 10 min microwave heating at 150 °C in a dedicated single-mode microwave reactor with internal temperature control. Carefully executed control experiments ensuring identical heating and cooling profiles, stirring rates, and reactor geometries have demonstrated that for these preparations of ZnO microrods no differences between conventional and microwave dielectric heating are observed. The resulting ZnO microrods exhibited the same crystal phase, primary crystallite size, shape, and size distribution regardless of the heating mode. Similar results were obtained for the ultrafast preparation of ZnO nanoparticles with diameters of approximately 20 nm, synthesized by means of a nonaqueous sol-gel process at 200 °C from a Zn(acac)(2) (acac=acetylacetonate) precursor in benzyl alcohol. The specific role of microwave irradiation in enhancing these nanomaterial syntheses can thus be attributed to a purely thermal effect as a result of higher reaction temperatures, more rapid heating, and a better control of process parameters.

Imprinting interference fringes in massive optomechanical systems

An interferometric scheme for the creation of momentum superposition states of mechanical oscillators, using a quantum mirror kicked by free photons is analyzed. The scheme features ultra-fast preparation with immediate detection and should allow for the observation of signatures of momentum superpositions in a massive macroscopic system at non-zero temperatures. It is robust against thermalized initial states, displacement and movement, mirror imperfections, and the measurements' back-actions.

Ultrafast Preparation of Three-Dimensional Dendritic Gold Nanostructures in Aqueous Solution and Their Applications in Catalysis and SERS

Three-dimensional dendritic gold nanostructures were prepared via an ultrafast one-step homogeneous solution method. Cationic surfactants, decane-1,10-bis(methylpyrrolidinium bromide) ([mpy-C10-mpy]Br2), were used as the capping agent and l-ascorbic acid (AA) was used as the reducing agent. The as-prepared gold dendrites present a [111] plane and grow along the ⟨211⟩ direction. The AA plays an important role in the formation of the dendritic nanostructures. The methylpyrrolidinium quaternary ammonium headgroups and bolaform nanostructures of the surfactants are the key factors for the formation of dendritic structures. Further investigation revealed that the reaction time and concentration of HAuCl4 weakly affect the formation of the dendrites. Moreover, the obtained gold dendrites exhibit excellent activity toward the catalytic reduction of p-nitraniline and higher enhancement of surface-enhanced Raman scattering when using Rhodamine 6G as the model molecules.

Selected tandem mass spectrometry ion monitoring for the fast identification of seafood species

Selected tandem mass spectrometry (MS/MS) ion monitoring (SMIM) is the most suitable scanning mode to detect known peptides in complex samples when an ion-trap mass spectrometer is the instrument used for the analysis. In this mode, the MS detector is programmed to perform continuous MS/MS scans on one or more selected precursors, either during a selected time interval, or along the whole chromatographic run. MS/MS spectra are recorded, so virtual multiple reaction monitoring chromatogram traces for the different fragment ions can be plotted. In this work, a shotgun proteomics approach was applied to the detection of previously characterized species-specific peptides from different seafood species. The proposed methodology makes use of high intensity focused ultrasound-assisted trypsin digestion for ultra fast sample preparation, peptide separation and identification by reverse phase capillary LC coupled to an ion-trap working in the SMIM scanning mode. This methodology was applied to the differential classification of seven commercial, closely related, species of Decapoda shrimps proving to be an excellent tool for seafood product authentication, which may be used by fisheries and manufacturers to provide a fast and effective identification of the specimens, guaranteeing the quality and safety of foodstuffs to consumers.

Laser Control of Ultrafast State-Selective Preparation of OH at High Vibrational Levels

An efficient laser control scheme for ultrafast state-selective preparation of vibrationally excited molecules close to the dissociation threshold with ultrashort infrared laser pulses has been developed and demonstrated by means of computer simulations for a one-dimensional dissociative model of OH in the electronic ground state. The control scheme for OH may include up to four laser pulses with properly optimized amplitudes, carrier frequencies, and overlaps. Simulations of the quantum dynamics in the classical laser field show that any prescribed high vibrational level of OH can be populated with selectivity close to 100%.