Fig 1

Four main branches of the article. (a) Control layer spacing to change the interlayer coupling; (b) Interaction between the guest and the host lattice; (c) Guest atoms create new properties; (d) Interlayer storage, such as lithium metal batteries. "

Fig 2

Studies on the change of interlayer spacing of MoS2 30. (a) Structural models of the oxygen-incorporated MoS2 with enlarged interlayer spacing and (b) the pristine 2H-MoS2. (c) XRD patterns of the products obtained at various temperatures. (d) FE-SEM images (A1–D1). TEM images (A2–D2) and cross-sectional TEM images (A3–D3) of the oxygen-incorporated MoS2 ultrathin nanosheets synthesized at various temperatures. Adapted from ACS Publications publisher. "

Fig 3

Studies on interlayer spacing and electrical transport properties of P-doped MoS232. (a) HRTEM images of sample (a, 1) P0, (a, 2) P8, and (a, 3) P24 and EDX spectra of P-doped MoS2 (a, 4). (b) The calculated band structures of undoped MoS2 (black lines) and P-intercalated MoS2 (red lines). The black dashed line indicates the Fermi energy. (c) The density of states of undoped MoS2 and P-intercalated MoS2. (d) Electronic charge density difference profiles of P-intercalated MoS2. The purple, yellow, and red balls represent the Mo, S, and P atoms, respectively. Adapted from ACS Publications publisher. "

Fig 4

First principle calculation of electronic properties of three-layer structures 9. (a) Computed band structures (PBE) of (a, 1) MoS2/MoSe2/MoS2, (a, 2) MoS2/WS2/MoS2, and (a, 3) MoS2/WSe2/MoS2 trilayer with ABA stacking, respectively. Computed band structures of (a, 4) MoS2/MoSe2 superlattice, (a, 5) MoS2/WS2 superlattice, and (a, 6) MoS2/WSe2 superlattice with the AB stacking, respectively. The green lines mark contribution from MoS2 layers while the red lines mark contribution from the MoSe2, WS2 or WSe2 layer. (b) Top view of a MoS2 monolayer in three different supercells (marked by the red parallelogram) and a BN monolayer in two different supercells. (c) Computed electronic band structures of (c, 1) monolayer MoS2; (c, 2) MoS2/vacuum layer/MoS2 by removing the BN layer from the MoS2/BN/MoS2 trilayer counterpart but with the fixed vertical location of the two MoS2 layers; (c, 3) MoS2/BN/MoS2 with the A1B1A1 stacking; and (c, 4) a 3D superlattice of MoS2/BN with the AB stacking. The green lines represent MoS2 layers while the red lines represent BN monolayer. Adapted from Royal Society of Chemistry publisher. "

Fig 5

TEM images, energy band calculations and transmission characteristics of a new stable superlattice prepared by electrochemical molecular embedding method 33. (a, b) Cross sectional TEM image comparison between BP (a) and MPMS (b). Scale bars: 3  nm. Insets are the corresponding electron diffraction pattern. Scale bars: 2  nm−1. (c, d) The corresponding high-resolution cross-sectional TEM images. Scale bars: 1  nm. (e) Three-dimensional views of the simulated atomic structure of MPMS. (f) The simulated electronic structure of MPMS, demonstrating the enlarged bandgap of 2.13  eV in MPMS as determined by the transition between first valence-band maximum, VBM-1 (green), and conduction-band minimum, CBM (red). (g, h) Back-gate transfer characteristics of pristine BP and MPMS as the source-drain bias is stepped from 0.1 V (black curve) to 0.5 V (green curve) bias. (i) Transfer characteristics at 0.01 V source-drain bias show an on/off ratio > 107 in MPMS versus < 10 in BP. Adapted from Springer Nature publisher. "

Fig 6

Catalytic activity of Li intercalation MoS2 42, 44. (a) Polarization curves of L-MoS2, S-MoS2, Li-MoS2, and Pt wire at a scan rate of 5 mV∙s−1. (b) Tafel plots of L-MoS2, S-MoS2, Li-MoS2, and Pt wire. Li-MoS2 shows the largest linear region. (c) Potentiostatic electrolysis of Li-MoS2 for 2 h. The potential we applied is 118 mV vs. RHE after iR correction. (d) LSV curves for the glass carbon electrode, commercial 20% (w) Pt/C catalyst, and as-exfoliated MoS2 nanosheets (1.0-0.001 A∙g−1). (e) Corresponding Tafel plots of the LSV curves in (d). (f) Chronopotentiometry curves of 0.001 A∙g−1 MoS2 QDs sheets and commercial 20% (w) Pt/C catalyst under a HER current density of 200 mA∙cm−2 for 80 h. Adapted from ACS Publications publisher. "

Fig 7

Study of inserting Cu or Co atoms to change the photoelectric properties of SnS2 39. (a) Schematics showing: (1) Bilayer pristine SnS2 with a van der Waals gap. (2) The S vacancy is the dominated defect type in the naturally CVD-grown SnS2, leading to an n-type semiconductor. (3) Cu-intercalated SnS2 as a p-type semiconductor. (4) Co-intercalated SnS2 as a highly conductive metal. Schematics between (2), (3) and (4) show that spatially controlled intercalation could realize the integration of these three elements. (b–d) Optical images of CVD-grown SnS2, Cu-SnS2 and Co-SnS2, respectively. Optical images clearly show that while the morphologies stay the same after intercalation, the colours of Cu-SnS2 and Co-SnS2 become more opaque and turn dark blue and violet-red, respectively, from the light blue colour of SnS2. (e) Raman spectra of SnS2, Cu-SnS2 and Co-SnS2 (from trilayer samples). (f) Relative reflectance ΔR of SnS2, Cu-SnS2 and Co-SnS2 on a SiO2/Si substrate showing apparent spectral changes as a result of intercalation, indicating significantly different optical properties. ΔR is defined as R(flake/SiO2/Si) – R(SiO2/Si). (g) Full XPS spectra show the presence of copper and cobalt after corresponding intercalation. (h) Demonstration of the ability to seamlessly integrate n-type SnS2, p-type Cu-SnS2 and metallic Co-SnS2 within a single piece of nanosheet. Scale bars in G, 20 μm. (i) I–V curves showing the nonlinear characteristics of SnS2 or Cu-SnS2 with a Ti/Au electrode, and Co-SnS2 can be used as the ohmic contact for both SnS2 and Cu-SnS2. (j) Typical rectification behaviour of the SnS2/Cu-SnS2 heterojunction, whose performance can be further improved by using Co-SnS2 as contact. Adapted from Springer Nature publisher. "

Fig 8

Synthesized a (TBA)Cr2Ge2Te6 hybrid superlattice with metallic behavior, and the Curie temperature is significantly increased 41. (a) Side-view crystal structure of Cr2Ge2Te6 and (TBA)Cr2Ge2Te6. (b) Left: Top-view structure of Cr2Ge2Te6. Right: Edge-sharing CrTe6 octahedrons form a honeycomb-like structure in the ab-plane and Cr spins interact through indirect 90° superexchange couplings with Te. (c) XRD patterns of pristine Cr2Ge2Te6 and intercalated (TBA)Cr2Ge2Te6 showing a series of (00l) diffractions. (d, e) Temperature-dependent magnetic susceptibility (M–T) of pristine Cr2Ge2Te6 and (TBA)Cr2Ge2Te6 with H//ab and H//c, respectively. (f, g) Magnetic field dependent magnetic susceptibility (M–H) of (TBA)Cr2Ge2Te6 with H//ab and H//c, respectively. Adapted from ACS Publications publisher. "

Fig 9

Synthesis and catalytic mechanism of cobalt single atom-intercalated MoS2 55. (a) Schematic of the electrochemical co-intercalation and subsequent annealing process to convert the intercalants into single atom catalyst. (b) SEM image showing the vertical structure of MoS2 array. (c) Atomic-resolution STEM-HAADF image of Co1-in-MoS2. Scale bar: (b) 2 μm; (c) 1 nm. (d) Proposed radical mediated pathway for sulfide oxidation. (e) Differential charge density of the optimized adsorption configuration (side view) of the sulfide 1q at the edge of bilayered Co1-in-MoS2. Purple and brown region represent the isosurface of the electron lost and gained. The color scheme used: dark cyan for Mo, yellow for S, blue for Co, gray for C, red for O, pink for B and white for H. (f) Difference in adsorption energies for various adsorption configurations of sulfide 1q on Co1-in-MoS2. (g) EPR experiments on trapping DMPO-OH adduct (marked as *) in sulfide oxidation. (1) Without H2O2 and catalyst; (2) without H2O2; (3) without sulfide 1a; and (4) standard conditions. Adapted from Wiley publisher. "

Fig 10

Structure and magnetic measurements on the intercalated transition metal dichalcogenide Fe1/3NbS256. (a) Magnetization (χ) measurements with field along the [001] direction (c axis) show a peak at 42  K in both the field cooled and zero-field cooled traces indicating the presence of an AFM transition. (b) In-plane magnetization measurements also show a weak peak at 42  K. A cooling field of 0.1  T was used for both a and b. (c) The crystal structure of Fe1/3NbS2 is that of 2H-NbS2 with iron atoms intercalated between layers. Adapted from Springer Nature publisher. "

Fig 11

Studies of self-intercalated Ta7S12 crystal 57. (a) Showing an abundance of interstitial Ta atoms at the center of honeycomb (b) or on top of the Ta site (c). (b, c) The corresponding atomic models are depicted on the right. (d) Schematic depicting the layer-by-layer growth of ic-2D crystals. (e, g) Hall resistance (Rxy) (e) and Temperature-dependent magnetoresistance (g) of Ta7S12 under an out-of-plane magnetic field. (f) Resistivity of the Ta7S12 ic-2D crystal as a function of temperature. (h) Contour plot of charge density difference in Ta-intercalated Ta7S12. (i, j) Orbital-resolved spin-up (i) and spin-down (j) band structures of the intercalated Ta in Ta7S12. (k) Top view (top) and side view (bottom) spin density isosurface of Ta-intercalated Ta7S12. (l) Calculated magnetic moments as a function of the Ta-intercalation concentration (σ) in 2Ha-stacked nonstoichiometric TaxSy. μB, Bohr magneton. Adapted from Springer Nature publisher. "