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Metal-organic structures are controllably prepared by tuning molecular size, supported substrates, and different kinds of metals. They are characterized by ultra-high vacuum low-temperature scanning tunnelling microscopy and Density functional theory calculations. The relatively larger size of all-trans-retinoic acid (ReA) compared to (2E,4E)-3-methyl-5-(2,6,6-trimethylcyclohex-1-enyl)penta-2,4-dienoic acid (DiA) leads to a bigger gap between neighboring ReA in a tetramer and allows for insertion of molecules, forming high density patterns. ReA forms various structures with different ratios (4:0, 3:1, 2:2) of the two chiral enantiomers on the less reactive Au(111) other than Ag(111). Unlike transition metals, electrostatic attraction between molecules and alkali metals is the origin of the formation of large quartet islands.

The self-assembly of l -tryptophan on Cu(111) is investigated by an ultrahigh vacuum scanning tunneling microscope (STM) at 4.4 K. When deposited onto the substrate at around 120 K with a coverage of 0.1 monolayer, molecular trimers, tetramers, hexamers, and chains coexist on Cu(111). Then almost all molecules self-assemble into chiral hexamers after being annealed at room temperature. When increasing molecular coverage to the full layer, a new type of chain is observed on the surface. Based on the high-resolution STM images at sub-molecular level, we suggest that the l -tryptophan molecules are present in neutral, zwitterionic or anionic states in these structures.

Using single molecule as a basic unit of storage devices is an appealing direction of device miniaturization. Tin-phthalocyanine (SnPc) molecules exhibit bistable adsorption configurations, Sn-up and Sn-down. A reversible conversion between these two configurations is readily manipulated and probed by scanning tunneling microscopy (STM). When SnPc molecules are used to form functional devices, they need to adsorb on supporting surfaces. So the growth mechanisms of ultra-thin films on metal surfaces or buffer layers have been investigated. Both layer-island (Stranski–Krastanov) and three-dimensional-island (Volmer–Weber) growth modes are observed in experiments. Because of an electronic decoupling of buffer layers, electronic and vibronic states of SnPc molecules are spectroscopically identified. Molecular switches between Sn-up and Sn-down configurations are achieved by either an electrical mean or mechanical forces. When the STM tip contacts SnPc molecules with controlled structures, electrons transports through single-molecule junctions are explored in detail. In addition, Ag–SnPc–Ag junction exhibits three conductance states at different voltages. These researches pave a way for further development of high-density data storage devices.

A new type of two-dimensional crystal comprising supramolecular pentamers on Au(111) is studied using an ultra-high vacuum low-temperature scanning tunnelling microscope. (2E,4E)-3-Methyl-5-(2,6,6-trimethylcyclohex-1-enyl)penta-2,4-dienoic acid molecules form pentamers through five-fold O⋯H–O hydrogen bonds. In ordered arrays, pentamers interact with each other via van der Waals interactions. The impacts of different annealing temperatures and substrates on the formation of pentamer patterns are systemically investigated.

Vehicle detection is the key component of driver assistance system based on computer vision. It is the basis for speed measurement, ranging and anti-collision. As an important part, it received wide attention and was developed rapidly in recent years. The complexity of the background environment and the real-time change brings great difficulty to vehicle detection. In this paper, a monocular camera is installed in front of the vehicle to collect images, and the digital image processing technology combined with machine learning is used for the vehicle detection. This process can be divided into two stages: the rapid positioning of the target and the target recognition. The experiments show that vehicles can be detected in the image quickly and effectively by this algorithm.

The self-assembly behavior of a V-shaped bispyridine, 1,3-bi(4-pyridyl)benzene (BPyB), was studied by scanning tunneling microscopy on the (111) surfaces of Cu, Ag, and Au. BPyB molecules coordinately bonded with active Cu adatoms on Cu(111) in the form of complete polygonal rings at low coverages. On Ag(111), BPyB molecules aggregated into two-dimensional islands by relatively weak intermolecular hydrogen bonds. The coexistence of hydrogen bonds and coordination interaction was observed on the BPyB-covered Au(111) substrate. Density functional theory calculations of the metal-molecule binding energy and Monte Carlo simulations were performed to help understand the forming mechanism of molecular superstructures on the surfaces. In particular, the comprehensive orbital composition analysis interprets the observed metal-organic complexes and reveals the importance of relativistic effects for the extraordinary activity of gold adatoms. The relativistic effects cause the energy stability of the Au 6s atomic orbital and decrease the energy separation between the Au 6s and 5d orbitals. The enhanced sd hybridization strengthens the N-Au-N bond in BPyB-Au-BPyB complexes.

Kinetically controlled hierarchical self-assemblies of all-trans-retinoic acid on Au(111) were investigated via low-temperature scanning tunneling microscopy in ultra-high vacuum. The dominant molecular hierarchical superstructure could be selectively controlled to dimer, tetramer, or pentamer patterns, which were stabilized by hydrogen bonds and van der Waals interactions.