Trajectory analysis and optimization of sea buckthorn fruit vibration separation manipulator based on I-PSO algorithm.

In this paper, the optimal time planning of vibration separation trajectory of Hippophae rhamnoides fruit is studied for space manipulator using the I-PSO algorithm. The first step is to analyze the motion of the robotic arm's joints, which are limited in range and speed, in combination with a 3-5-3 polynomial interpolation, an improved Particle swarm optimization with adaptive inertia weight and asynchronous learning factor is proposed, and the specific process is given. Experimental images and data show that the improved particle swarm optimization algorithm can ensure the continuity of joint acceleration and velocity, and the optimal vibration trajectory time is 0.536539094 s Compared with the planned system trajectory time of 0.71022 s, the speed increased by 24.5%. The results of the orthogonal experiment show that the average fruit drop rate reaches 96.19%, which verifies the validity and reliability of the I-PSO algorithm for optimal time planning of seabuckthorn fruit separation vibration trajectory.

Solvent-mediated precipitating synthesis and optical properties of polyhydrido Cu13 nanoclusters with four vertex-sharing tetrahedrons.

Structurally defined metal nanoclusters facilitate mechanism studies and promote functional applications. However, precisely constructing copper nanoclusters remains a long-standing challenge in nanoscience. Developing new efficient synthetic strategies for Cu nanoclusters is highly desirable. Here, we propose a solvent-mediated precipitating synthesis (SMPS) to prepare Cu13H10(SR)3(PPh3)7 nanoclusters (H-SR = 2-chloro-4-fluorobenzenethiol). The obtained Cu13 nanoclusters are high purity and high yield (39.5%, based on Cu atom), proving the superiority of the SMPS method. The Cu13 nanoclusters were comprehensively studied via a series of characterizations. Single crystal X-ray crystallography shows that the Cu13 nanoclusters contain a threefold symmetry axis and the Cu13 kernel is protected by a monolayer of ligands, including PPh3 and thiolates. Unprecedentedly, the aesthetic Cu13 kernel is composed of four vertex-sharing tetrahedrons, rather than the common icosahedral or cuboctahedral M13. The intramolecular π⋯π interactions between thiolates and PPh3 on the surface contribute to the stable configuration. Furthermore, electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) revealed the existence of ten hydrides, including four types of hydrides. Density functional theory (DFT) calculations without simplifying the ligands simulated the location of the 10 hydrides in the crystal structure. Additionally, the steady-state ultraviolet-visible absorption and fluorescence spectra of the Cu13 nanoclusters exhibit unique optical absorbance and photoluminescence. The ultrafast relaxation dynamics were also studied via transient absorption spectroscopy, and the three decay components are attributed to the relaxation pathways of internal conversion, structural relaxation and radiative relaxation. This work provides not only a novel SMPS strategy to efficiently synthesize Cu13 nanoclusters, but also a better insight into the structural characteristics and optical properties of the Cu nanoclusters.

Atomically precise structures of Pt2(S-Adam)4(PPh3)2 complexes and catalytic application in propane dehydrogenation.

As a bridge between single metal atoms and metal nanoclusters, atomically precise metal complexes are of great significance for controlled synthesis and catalytic applications at the atomic level. Herein, novel Pt2(S-Adam)4(PPh3)2 complexes were prepared via the conventional synthetic methods of metal nanoclusters. The atomically precise crystal structures of the binuclear Pt complexes with three kinds of packing modes in a unit cell were determined by X-ray crystallography. The two Pt atoms are bridged by two S atoms of thiolates, constructing a rhombus on a plane. Moreover, the ultraviolet visible absorption spectra of Pt2(S-Adam)4(PPh3)2 complexes show an apparent absorption peak centered at 454 nm. Furthermore, the Pt complexes were used as precursors to prepare catalysts for non-oxidative propane dehydrogenation. The as-prepared Pt-based catalysts with a particle size of approximately 1 nm demonstrated a propane conversion of about 18% and significantly enhanced selectivity for propylene, up to 93%. Our work will be beneficial to the basic understanding of platinum complexes, as well as the improvement of the catalytic dehydrogenation of propane.

The doping engineering and crystal structure of rod-like Au8Ag17 nanoclusters.

Alloy nanoclusters protected by ligands were widely studied due to the synergistic effect of metal atoms, and they exhibit enhanced properties in different fields, such as bio-imaging and catalysis. Herein, we obtained Au8Ag17(PPh3)10Cl10 nanoclusters via one-step simple synthesis. The atomically precise crystal structure was determined by x-ray crystallography. It is found that the rod-like Au8Ag17 nanoclusters were composed of two Au4Ag9 icosahedrons via sharing the same Ag atom. Two Au atoms occupy the center of icosahedrons, and the other six Au atoms are all at the neck sites. Four kinds of Cl-Ag connecting modes were observed in Au8Ag17 nanoclusters. Moreover, the ultraviolet-visible absorption spectrum shows that the prominent absorption peaks of Au8Ag17 nanoclusters are at ∼395 and 483 nm. This work provides a feasible strategy to synthesize alloy nanoclusters with precise composition via doping engineering.

Synthesis and Optical Properties of Unique Pt1Ag24 Nanoclusters with Mixed Exterior Motif Structures.

The atomic arrangement of metal nanoclusters plays a significant role in the structure-property correlation. Herein, we present a novel Pt1Ag24(SR)16(PPh3)3 nanocluster with a unique structure, different from two reported Pt1Ag24 nanoclusters. The nanocluster was prepared via one-pot synthesis and solvent extraction. It has a centered icosahedral Pt1Ag12 kernel and an open shell composed of three Ag2(SR)3(PPh3) staple motifs and a unique trefoil-like Ag6(SR)7 motif. The three kinds of Pt1Ag24 nanoclusters have the same kernel but different shell configurations. The fine-tuning of structures is necessary and significant for the investigation of the relationship of structures and properties. The different UV-vis absorption spectra indicate that the optical properties of three Pt1Ag24 nanoclusters mainly depend on the exterior shell configuration and the metal-ligand interface. This work provides insights toward growth mechanism and the structure-property correlation of metal nanoclusters.

[AuAg26(SR)18S]- Nanocluster: Open Shell Structure and High Faradaic Efficiency in Electrochemical Reduction of CO2 to CO.

For atomically precise metal nanoclusters, distinctive molecular architectures and promising applications are urgently required to be intensively explored. Herein, we have first reported the open shell structure of the [AuAg26(S-Adm)18S]- nanocluster and its application in the electrochemical reduction of CO2. The X-ray crystal structure of the AuAg26 nanocluster is composed of a AuAg12 icosahedron kernel and a Ag14(SR)18S open shell. The shell includes a Ag6(SR)3S, a Ag5(SR)6, and three Ag(SR)3 motifs. It is the first time twisty propeller-like Ag5(SR)6 and trefoil-like Ag6(SR)3S motifs in metal nanoclusters have been observed. Due to the novel open shell configuration of Ag14(SR)18S, four triangular facets of the kernel are exposed. The AuAg26 nanocluster shows excellent catalytic activity in the electrochemical reduction of CO2 to CO. The Faradaic efficiency of CO is up to 98.4% under -0.97 V. The electrochemical in situ infrared study and DFT calculations demonstrate that the open shell structure of the AuAg26 nanocluster is beneficial to the forming of intermediate COOH* in the electrochemical reduction of CO2 to CO.

The synthesis and structure of the [PdAu13(PPh3)3(SR)7]+ nanocluster.

Metal alloy nanoclusters have attracted increasing attention due to the synergistic effect of the foreign atoms. For the first time the synthesis and crystal structure of the [PdAu13(PPh3)3(SR)7]+ nanocluster is reported. The crystal structure of the nanocluster was determined by single crystal X-ray diffraction. The [PdAu13(PPh3)3(SR)7]+ nanocluster has a concave polyhedron Au9Pd kernel, which looks like a girl dancing ballet. The structure shows that [PdAu13(PPh3)3(SR)7]+ has an open shell. Meanwhile, we also carried out ultraviolet-visible (Uv-vis) absorption spectroscopy and fluorescence spectroscopy to study the optical properties of the [PdAu13(PPh3)3(SR)7]+ nanocluster.

Structure of the Au23-x Agx (S-Adm)15 Nanocluster and Its Application for Photocatalytic Degradation of Organic Pollutants.

Ligands play an important role in determining the atomic arrangement within the metal nanoclusters. Here, we report a new nanocluster [Au23-x Agx (S-Adm)15 ] protected by bulky adamantanethiol ligands which was obtained through a one-pot synthesis. The total structure of [Au23-x Agx (S-Adm)15 ] comprises an Au13-x Agx icosahedral core, three Au3 (SR)4 units, and one AgS3 staple motif in contrast to the 15-atom bipyramidal core previously seen in [Au23-x Agx (SR)16 ]. UV/Vis spectroscopy indicates that the HOMO-LUMO gap of [Au23-x Agx (S-Adm)15 ] is 1.5 eV. DFT calculations reveal that [Au19 Ag4 (S-Adm)15 ] is the most stable structure among all structural possibilities. Benefitting from Ag doping, [Au23-x Agx (S-Adm)15 ] exhibits drastically improved photocatalytic activity for the degradation of rhodamine B (RhB) and phenol under visible-light irradiation compared to Au23 nanoclusters.

Cu2+ -Induced Structural Isomers: Effect of Foreign Metal Ions on the Structure and Properties of Silver Nanoclusters.

Metal ions have an important impact on the precise control of the synthesis and atomic structural arrangement of noble metal nanoclusters. In this work, the effect of metal ions on the isomer generation of metal nanoclusters is revealed for the first time. Compared with the previous Ag23 nanoclusters with two face-centered cubic (fcc) unit cells twisting 27°, the Ag23 isomer had a higher symmetry structure with two fcc unit cells almost overlapping. In addition, the UV/Vis absorption spectrum of the isomer showed a slight redshift of approximately 14 nm. The redshift might be because of the modulation of electronic structure, which is derived from fine-tuned crystal structure. Based on the experimental results, we provide mechanisms to explain the Cu2+ effect on the structural isomer. This work reports a significant finding to tune precisely the crystal structure and understand the mechanism of shape-controlled synthesis of metal nanoclusters.

Cluster-to-cluster transformation among Au6, Au8 and Au11 nanoclusters.

We present the cluster-to-cluster transformations among three gold nanoclusters, [Au6(dppp)4]2+ (Au6), [Au8(dppp)4Cl2]2+ (Au8) and [Au11(dppp)5]3+ (Au11). The conversion process follows a rule that states that the transformation of a small cluster to a large cluster is achieved through an oxidation process with an oxidizing agent (H2O2) or with heating, while the conversion of a large cluster to a small one occurs through a reduction process with a reducing agent (NaBH4). All the reactions were monitored using UV-Vis spectroscopy and ESI-MS. This work may provide an alternative approach to the synthesis of novel gold nanoclusters and a further understanding of the structural transformation relationship of gold nanoclusters.

Reversible conversion between phosphine protected Au6 and Au8 nanoclusters under oxidative/reductive conditions.

In this study, we found that phosphine protected [Au6(dppp)4]2+ and [Au8(dppp)4Cl2]2+ nanoclusters could be reversibly converted under oxidative/reductive conditions. This work not only provides new insights into the relationship between the [Au6(dppp)4]2+ and [Au8(dppp)4Cl2]2+ nanoclusters, but also offers a novel method for controlling structural evolution of different Au nanoclusters.