A Molten-Salt Method to Synthesize Ultrahigh-Nickel Single-Crystalline LiNi0.92 Co0.06 Mn0.02 O2 with Superior Electrochemical Performance as Cathode Material for Lithium-Ion Batteries.

Ni-rich layered oxides have been intensively considered as promising cathode materials for next-generation Li-ion batteries. Nevertheless, the performance degradation caused by intergranular cracks and electrode/electrolyte interface parasitic reactions restricts their further application. Compared with secondary particles, single-crystal (SC) materials have better mechanical integrity and cycling stability. However, the preparation of ultrahigh-nickel layered SC cathode still remains a serious challenge. Herein, a novel LiOH-LiNO3 -H3 BO3 molten-salt method is proposed to synthesize SC LiNi0.92 Co0.06 Mn0.02 O2 with considerable crystallinity and uniformity. The critical impacts of calcination temperature and boric acid on the microstructure and electrochemical property of Ni-rich layered oxides are systematically investigated. The results show that the crystal growth is promoted and the stability of crystal structure is improved by this synthesis method. In particular, the optimal electrode demonstrates a superior initial discharge capacity of 214.8 mAh g-1 with a high capacity retention of 86.3% over 300 cycles as tested by pouch-type full cells at 45 ºC. This work not only prepares an ultrahigh-nickel layered CS cathode with superior electrochemical performances, but also provides a feasible method for the synthesis of other CS layered cathode materials.

Regulation and enhancement of the nonlinear optical properties of reduced graphene oxide through Au nanospheres and Au@CdS core-shells.

Regulating nonlinear optical (NLO) absorption and refraction properties of graphene is significant in nonlinear photonics. In this work, the functionalizing strategy of quantum dots (QDs) was used for the regulation of the NLO properties of reduced graphene oxide (rGO) with Au nanospheres and Au@CdS core-shells. The third-order NLO properties of rGO-Au and rGO-Au@CdS nanocomposites were investigated by Z-scan technique with 38 ps laser pulses at 532 nm wavelength. The saturation absorption (SA) of rGO was weakened when it was combined with Au nanospheres and switched to reverse saturation absorption (RSA) when combined with Au@CdS core-shells as irradiance intensity increased. The strength of RSA was tunable with the size of Au@CdS core-shells. Meanwhile, the nonlinear susceptibility of rGO was weakened with the complex Au but was tunable with the complex Au@CdS and realized two times enhancement. The effect of charge transfer mechanism was proposed to explain the regulated effect.

Characteristics of fork-shaped fringes formed by off-axis interference of two vortex beams.

Fork-shaped fringes are formed for off-axis interference between two oblique-incident vortex beams. New formulas considering various parameters [such as the angles between two vortex beams and their topological charges (TCs)] are established to describe all kinds of fork-shaped fringes. An improved Mach-Zehnder interferometer is employed to investigate these interference fringes. Experimental measurements are consistent with numerical simulations by using our formulas. Our results broaden the understanding of the off-axis interference between two vortex beams, and can be applied to detect the TCs' sign and value of an unknown vortex beam, especially large-value TCs.

Size confinement and origins of two-photon absorption and refraction in CdSe quantum dots.

Tuning a semiconductor nanomaterial with large two-photon absorption cross section in the near-infrared wavelength and investigating the correlation and origins between its size and third-order nonlinear optical properties are very important in possible applications. In this work, CdSe quantum dots (QDs) with various sizes were successfully prepared, and their size-confined third-order nonlinear optical properties were investigated by Z-scan technique with 100 fs laser pulses at 800 nm wavelength. Both the two-photon absorption and nonlinear refraction were enhanced about 8.1 times with size decrease and then weakened to 2 times with further size decrease. QDs with the diameter of 4.9 nm had the largest nonlinear optical susceptibility of 7.8 × 10-12 esu. The effects of photoinduced dipole moment and local electric field were proposed to explain this trend. And the intrinsic dipole moment and defects in CdSe QDs also had an effect on this nonlinear process.

Retraction: Comprehensive insights into the charge dynamics process and excellent photoelectric properties of heterojunction solar cells.

Retraction of 'Comprehensive insights into the charge dynamics process and excellent photoelectric properties of heterojunction solar cells' by Xiangyang Liu et al., Phys. Chem. Chem. Phys., 2016, 18, 24299-24306.

Surface oxygen-containing defects of graphene nanosheets with tunable nonlinear optical absorption and refraction.

Surface oxygen-containing defects of graphene nanosheets (G NSs) are important for the nonlinear optical (NLO) properties in optoelectric devices. G NSs with different surface oxygen-containing defects are successfully tuned by a chemical reduction process, and are characterized by several experimental measurements of morphology and structure and by spectroscopy. Their NLO properties are measured with the Z-scan technique and the NLO transmission method using a 30 picosecond single-pulse laser source at 532 nm wavelength. Their NLO susceptibility is enhanced 11.8 times (from 0.38 × 10-12 esu to 4.5 × 10-12 esu) with the decrease in the density of surface oxygen-containing groups, while it is reduced 7.2 times (2.7 × 10-12 esu) with a further decrease in oxygen. Accordingly, the nonlinear absorption coefficient of graphene is increased from 0.51 cm GW-1 to 5.90 cm GW-1, and then decreased to 3.41 cm GW-1, indicating that the NLO response of graphene NSs should be weakened whether the component of surface oxygen-containing groups is too large or too small. The local field effect arising from surface oxygen-containing groups and isolated sp2 clusters is the dominant mechanism for the NLO improvement, while the connection of small sp2 clusters depresses the optical nonlinearity. An evolution from two-photon absorption to saturable absorption with the decrease of surface oxygen concentration is obtained. The intensity-related NLO absorption and refraction in NSs are also discussed. Tuning the surface oxygen-containing defects of graphene is a useful way to enhance the optical nonlinearity for potential applications in devices.

Correction: Comprehensive insights into the charge dynamics process and excellent photoelectric properties of heterojunction solar cells.

Correction for 'Comprehensive insights into the charge dynamics process and excellent photoelectric properties of heterojunction solar cells' by Xiangyang Liu et al., Phys. Chem. Chem. Phys., 2016, 18, 24299-24306.

Self-accelerating Airy-Laguerre-Gaussian light bullets in a two-dimensional strongly nonlocal nonlinear medium.

We report a self-accelerating wave packets eigenmode solution of a two-dimensional (2D) nonlocal nonlinear Schrödinger equation (NNLSE) with an Airy-beam time-dependence, and present their spatiotemporal profiles. The behaviours of such Airy-Laguerre-Gaussian light bullets, as propagated in a strongly nonlocal nonlinear medium (SNNM), are investigated both analytically and numerically. We found that the generation, control, and manipulation of the NL spatiotemporal light bullets are affected by the radial mode number and the azimuthal mode number, as well as the modulation depth. Our scheme is quite different from the linear light bullets, in which the wave propagates in a NL medium and is an eigenmode of NLSE.

Comprehensive insights into the charge dynamics process and excellent photoelectric properties of heterojunction solar cells.

Zn2SnO4 octahedron nanoparticles/Cu4Bi4S9 (ZTO/CBS) and ZTO octahedron nanoparticles/CBS-graphene nanoplatelets (ZTO/CBS-GNs), as well as two types of bulk heterojunction (BHJ) solar cells with high flexibility were prepared on stainless steel meshes (SSMs). The improved photovoltaic responses of CBS-GNs and ZTO/CBS-GNs with the incorporation of graphene nanoplatelets were determined using surface photovoltage spectroscopy (SPS). The signals of time-resolved fluorescence response (TFR) and transient surface photovoltage (TPV) can provide more detailed information on the transition, separation and transport of photogenerated carriers. Here, the ZTO/CBS-GNs cell exhibits a superior performance and the highest efficiency is 8.6%. The multichannel separation process from the TPV signals indicates that the macro-photoelectric signals can be attributed to photogenerated charges separated at the interface of CBS/GNs, rather than CBS/ZTO. The comprehensive signals of SPS, TFR and TPV not only provide insights into the transition, separation and shifting of photogenerated carriers, but also promote the exploration of charge dynamics from the picosecond to second range. Importantly, the BHJ flexible solar cells with excellent efficiency and facile, scalable production present significant potential for practical application.

Transport of photogenerated charges and photoelectric properties in two types of heterostructures with different ZnO microstructures.

ZnO films with several microstructures including nanoparticles, nanowire arrays, nanorod arrays and nanotube arrays were prepared using different methods. In2O3 and/or Cu4Bi4S9 were deposited onto each nanostructured ZnO film, and two types of heterostructures (ZnO/Cu4Bi4S9 and ZnO/In2O3/Cu4Bi4S9) as well as solid state dye-sensitized solar cells were fabricated. The signals of steady state and electric field-induced surface photovoltage spectroscopy indicate that all of ZnO/In2O3/Cu4Bi4S9 heterostructures exhibit higher photovoltaic response than the relative ZnO/Cu4Bi4S9. The same type of heterostructure with different ZnO films presents various photovoltaic properties. Transient surface photovoltage spectroscopy can contribute to study the separation and transport mechanism of photogenerated charges. Here, ZnO nanotubes/Cu4Bi4S9 and ZnO nanotubes/In2O3/Cu4Bi4S9 cells exhibit the best performances with the highest efficiencies of 6.2% and 6.8%, respectively. The internal relations of photoelectric properties to some factors, such as film thickness, surface area, microstructure, double energy level matchings, etc. were discussed in detail. Qualitative and quantitative analysis further verified the comprehensive effect and the difference of factors. The exploration to understand the transport mechanism of light-induced charges in composite films will promote the nanocrystal application in solid state solar cells and photovoltaic community.

Site-specific protein dynamics in communication pathway from sensor to signaling domain of oxygen sensor protein, HemAT-Bs: Time-resolved Ultraviolet Resonance Raman Study.

HemAT-Bs is a heme-based signal transducer protein responsible for aerotaxis. Time-resolved ultraviolet resonance Raman (UVRR) studies of wild-type and Y70F mutant of the full-length HemAT-Bs and the truncated sensor domain were performed to determine the site-specific protein dynamics following carbon monoxide (CO) photodissociation. The UVRR spectra indicated two phases of intensity changes for Trp, Tyr, and Phe bands of both full-length and sensor domain proteins. The W16 and W3 Raman bands of Trp, the F8a band of Phe, and the Y8a band of Tyr increased in intensity at hundreds of nanoseconds after CO photodissociation, and this was followed by recovery in ∼50 µs. These changes were assigned to Trp-132 (G-helix), Tyr-70 (B-helix), and Phe-69 (B-helix) and/or Phe-137 (G-helix), suggesting that the change in the heme structure drives the displacement of B- and G-helices. The UVRR difference spectra of the sensor domain displayed a positive peak for amide I in hundreds of nanoseconds after photolysis, which was followed by recovery in ∼50 µs. This difference band was absent in the spectra of the full-length protein, suggesting that the isolated sensor domain undergoes conformational changes of the protein backbone upon CO photolysis and that the changes are restrained by the signaling domain. The time-resolved difference spectrum at 200 µs exhibited a pattern similar to that of the static (reduced - CO) difference spectrum, although the peak intensities were much weaker. Thus, the rearrangements of the protein moiety toward the equilibrium ligand-free structure occur in a time range of hundreds of microseconds.

A separation mechanism of photogenerated charges and magnetic properties for BiFeO3 microspheres synthesized by a facile hydrothermal method.

BiFeO(3) (BFO) microspheres were synthesized by a facile hydrothermal method. The optical absorption spectrum indicates that on site Fe(3+) crystal-field transitions and the charge transfer excitations can be observed. Magnetic measurements show a spin-glass behavior and room temperature weak ferromagnetism. The surface photovoltage spectroscopy of the BFO shows two response peaks centered at about 370 and 400 nm, respectively. Under an ambient atmosphere, the maximum surface photovoltage of the BFO reaches 180 µV with the bias (+2 V) and is three times larger than that with zero bias. It is found that the surface photovoltage response intensity increases with an increase in applied bias, regardless of positive or negative bias. It is suggested that the surface photovoltaic properties are related to both the depolarization field owing to ferroelectric polarization and the build-in electric field due to the Schottky barrier. The micro-process and the physical mechanism of the separation of photogenerated charges for BFO are fully explained.

Slightly off-axis interferometry for microscopy with second wavelength assistance.

Slightly off-axis interferometry for microscopy has been performed, where the dc term of the interferogram is suppressed by the object wave in another wavelength. One wavelength of the laser beam (red light) is used to generate the slightly off-axis interferogram, while the second wavelength (blue light) is employed to measure the transmittance of the specimen. Both the red light and blue light are recorded simultaneously by a color CCD camera and can be separated without cross talk via the red-green-blue components. The dc term of the slightly off-axis interferogram of red light is suppressed with the object wave of blue light. As a consequence, the requirement on the off-axis angle between the object and reference waves is relaxed as well as the requirement on the resolving power of CCD camera.

Synthesis and Third-Order Nonlinear Synergistic Effect of ZrO2/RGO Composites.

Tuning the third-order nonlinear properties of graphene by hybrid method is of great significance in nonlinear optics research. ZrO2/reduced graphene oxide (RGO) composites with different ZrO2 concentrations were prepared by a simple hydrothermal method. The morphology and structure show that ZrO2 nanoparticles were uniformly dispersed on the surface of graphene nanosheets. The nonlinear optical (NLO) characteristics of composites with different ZrO2 concentrations were studied by the Z-scan technique of 532 nm picosecond pulsed laser. The results showed that ZrO2/RGO composites had saturated absorption and positive nonlinear refraction characteristics. Meanwhile, the third-order nonlinear susceptibility of the ZrO2/RGO composite with a 4:1 mass ratio of ZrO2 to graphene oxide could reach 23.23 × 10-12 esu, which increased tenfold compared to RGO, and the nonlinear modulation depth reached 11.22%. Therefore, the NLO characteristics could be effectively adjusted by controlling the concentration of ZrO2, which lays a foundation for further research on the application of ZrO2/RGO composites in NLO devices.

Absorption spectroscopic properties of AgSiO cluster: a time-dependent density functional theory study.

The absorption spectra of different AgSiO isomers have been studied in the framework of the time-dependent density functional theory and related techniques employing relativistic effective core potential in order to identify the AgSiO ground state structure. And the transition energies and oscillator strengths of the stable structure and the isomeric forms are also investigated. Considering the binding energy and calculated absorption spectra of AgSiO, in combination with experimental data, we find that the ground state structure of AgSiO holds an obtuse triangular structure with a bond angle (triangle Ag-Si-O) of 119 degrees.

Density-functional study of structural, electronic, and magnetic properties of the EuSi(n) (n=1-13) clusters.

The geometries, stabilities, and electronic and magnetic properties of europium encapsulated EuSi(n) (n=1-13) clusters have been investigated systematically by using relativistic density functional theory with generalized gradient approximation. Starting from n=12, the Eu atom completely falls into the center of the Si frame, i.e., EuSi(12) is the smallest fully endohedral Eu silicon cluster. The interesting finding is in good agreement with the recent experimental results on the photoelectron spectroscopy of the europium silicon clusters [A. Grubisic, H. P. Wang, Y. J. Ko, and K. H. Bowen, J. Chem. Phys. 129, 054302 (2008)]. The magnetic moments of the EuSi(n) (n=1-13) clusters are also studied, and the results show that the total magnetic moments of the EuSi(n) clusters and the magnetic moments on Eu do not quench when the Eu is encapsulated in the Si outer frame cage. It is concluded that most of the 4f electrons of the Eu atom in the EuSi(12) cluster do not interact with the silicon cage and the total magnetic moments are overwhelming majority contributed by the 4f electrons of the Eu atom. According to the binding energy per atom, the second difference in energy (Delta(2)E), and vertical ionization potential, the EuSi(n) (n=4,9,12) clusters are very stable.

Tunable Nonlinear Optical Property of MnS Nanoparticles with Different Size and Crystal Form.

It is significant to study the reason that semiconductor material has adjustable third-order optical nonlinearity through crystal form and dimensions are changed. αMnS nanoparticles with different crystal forms and sizes were successfully prepared by one-step hydrothermal synthesis method and their size-limited third-order nonlinear optical property was tested by Z-scan technique with 30 ps laser pulses at 532 nm wavelength. Nanoparticles of different crystal forms exhibited different NLO (nonlinear optical) responses. γMnS had stronger NLO response than αMnS because of higher fluorescence quantum yield. Two-photon absorption and the nonlinear refraction are enhanced as size of nanoparticlesreduced. The nanoparticles had maximum NLO susceptibility which was 3.09 × 10-12 esu. Susceptibility of αMnS increased about nine times than that of largest nanoparticles. However, it was reduced when size was further decreased. This trend was explained by the effects of light induced dipole moments. And defects in αMnS nanoparticles also had effect on this nonlinear process. MnS nanoparticles had potential application value in optical limiting and optical modulation.

Facile One-Step Synthesis and Enhanced Optical Nonlinearity of Graphene-γMnS.

Graphene-γMnS were prepared by facile one-step hydrothermal method. Structures and properties of samples were explored by characterization, and nonlinear optical (NLO) enhancement of nanocomposites (NCs) was fully studied. Nanoparticles and NCs were tested at 532 nm by a Z-scan technique. With γMnS attached in G layers, NLO susceptibility of graphene-γMnS was greatly improved under single-pulse laser irradiation compared with G and γMnS. The nonlinearity enhanced was attributed to local field effect and charge transfer between γMnS and graphene layers. And NLO property enhancement was restricted by non-radiative defects in graphene-γMnS. Exploring the mechanism of nonlinearity enhancement was significant for fabrication of NLO devices. However, the optical nonlinearity decreased first and then increased with further increased addition of GO, because the dispersion of γMnS attached on graphene surface might make density of sp2 fragment and defects changed. Graphene-γMnS exhibited excellent and tunable NLO performance, illustrating that NCs materials have potential applications in NLO devices.

A Facile Method to Synthesize CdSe-Reduced Graphene Oxide Composite with Good Dispersion and High Nonlinear Optical Properties.

CdSe-reduced graphene oxide (CdSe/RGO) composites were synthesized by a hydrothermal method. CdSe/RGO composites with different mass ratios were prepared. The structure and morphology of CdSe/RGO composites were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesis of CdSe/RGO complexes was successfully demonstrated by Fourier infrared (FT-IR) and Raman spectra. CdSe nanoparticles in the CdSe/RGO composite were uniformly dispersed on the graphene surface. The study found that oxygen-containing functional groups such as hydroxyl (-OH) and carboxyl (-COOH) groups in graphene played a decisive role in the dispersion of CdSe. The third-order nonlinear optical properties of CdSe/RGO composites were measured by a single beam Z-scan technique. The experimental results showed that composites exhibited two-photon absorption and self-focusing nonlinear refraction properties. Additionally, the third-order nonlinear susceptibility of the composite material was obviously enhanced, which was mainly due to the good dispersion of CdSe nanoparticles on graphene.

Large irradiance limiting induced by three-photon absorption of a symmetrical fluorene-based molecule.

Herein, three-photon absorption (3PA) effect of a symmetrical fluorene-based molecule, pumped with 38 ps Q-switched 1064 nm laser pulses, is reported. An accurate Gaussian fitting method is used to obtain the three-photon absorption cross-section. The obtained three-photon absorption cross-section, 8.54 x 10(-76) cm(6) s(2), is very high. The irradiance limiting nonlinear transmittance is as low as 2% when the incident irradiance is 120 GW/cm(2). The geometry and electronic transition of the molecule are systematically studied by AM1 and TD SCF/DFT methods.