Fig 1

Schematic of Sol-gel process for preparation of oxide and metal materials"

Table 1

Metallic nanocrystals being prepared by Sol-gel method."

Fig 2

XRD profiles of Co, Ni, Cu, Ag, Bi and Co0.5Ni0.5 nanoparticles (a) and TEM images of Co0.5Ni0.5 nanoparticles prepared by using citric acid mediated sol-gel process 13. Adapted from John Wiley and Sons publisher."

Fig 3

XRD profiles of the products being calcinated at different temperatures by applying ethylene glycol mediated Sol-gel process where the molar ratio of Ni(NO3)2·6H2O: ethylene glycol is 1 : 1."

Fig 4

XRD analysis results of Ni nanocrystals being calcinated at different temperatures by using sol-gel process. (a) L-arabinise was chelating agent, Ni(NO3)2·6H2O was nickel source, PVP was surfactant, and solvent was de-ionized water; (b) 1, 2-benzenediol was chelating agent, Ni(NO3)2·6H2O was nickel source, PVP was surfactant, and solvent was de-ionized water; (c) citric acid was chelating agent, Ni(acac)2 was nickel source, octadecylamine was surfactant, and solvent was absolute ethanol. (d) glutaraldyde was chelating agent, Ni(acac)2 was nickel source, tween 20 was surfactant, and solvent was absolute ethanol."

Fig 5

XRD profiles of the precursors and products being calcinated at different temperatures by applying citric acid (a) and lactic acid (b) as chelating agent, de-ionized water and AgNO3 as solvent and solute, tween 20 as surfactant, respectively."

Fig 6

XRD patterns of the Ag, Pt, Pd, Cu, Ni nanocrystals prepared by using starch as chelating agent, de-ionized water as solvent 20. Adapted from Royal Society Chemistry publisher."

Fig 7

XRD patterns of the precursor and products being calcinated at different temperatures by employing agar as chelating agent, de-ionized and H6TeO6 as solvent and solute."

Fig 8

XRD patterns of the Cu3Pt products being calcinated at different temperatures by employing starch as chelating agent, de-ionized as solvent 20. Adapted from Royal Society Chemistry publisher."

Fig 9

XRD profiles (a), TEM image (b) and room temperature magnetic hysteresis loop (c) of FePt nanocrystals being calcinated at 700 ℃ by using glycine as chelating agent, de-ionized as solvent 19. Adapted from American Institute of Physics publisher."

Fig 10

XRD analysis results (a) and TEM image (b) of CoCrCuNiAl nanocrystals being calcinated at 300 ℃ by using citric acid as chelating agent, de-ionized as solvent 76. Adapted from Nature publisher."

Fig 11

Theoretical results of the change of Gibbs free energies based on thermodynamical calculation 21. Adapted from Royal Society Chemistry publisher."

Table 2

The classification of first, second and third types of metallic elements according to thermodynamical calculation."

Fig 12

XRD patterns of CdTe nanocrystals being calcinated at 550 ℃ by using citric acid (a) and gelatin (b) as chelating agent 21. Adapted from Royal Society Chemistry publisher."

Fig 13

P rinciples of sol-gel method and conventional liquid phase reducing methods 21. Adapted from Royal Society Chemistry publisher."

Fig 14

XRD analysis results of Ni3Fe nanocrystals prepared by using extract of leaf of fatsia japonica as chelating agent."

Fig 15

Magnetization?temperature (M–T) curves of Ni3Fe nanocrystals being calcinated at 300 ℃ (a) and 750 ℃ (b) by using L-isoleucine as chelating agent 10. Adapted from Elsevier publisher."

Fig 16

Schematic of the preparation of CoNi@NC electrocatalyst by applying Na4EDTA, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O (a-d), XRD profiles of CoNi@NC nanomaterials being calcinated at different temperatures (e) and HRTEM image of CoNi@NC nanomaterials being caicinated at 475 ℃ 104. Adapted from John Wiley and Sons publisher."

Fig 17

TEM images of the products being calcinated at 700 ℃ followed by acid etching where citric acid, nickel acetate, cyanamide have been used as raw materials with LiNO3 (a), and without LiNO3 (b) 106, the XRD patterns (c) and catalytic behavior for oxygen evolution reaction of the products (d) 106. Adapted from Elsevier publisher."

Fig 18

TEM images of porous carbon coated Ni (a, b) and Co (c, d) nanocrystals, and XRD profiles (e) of Ni@NCand Co@NC nanocrystalsbeing calcinated nated at 650 ℃ by using glycerol, ferric nitrate, cobalt nitrate, nickel nitrate 107. Adapted from Elsevier publisher."

Fig 19

Schematic of preparation of various kinds of 2D materials by using gel-blowing method (a), image of the gel precursor (b), the dried gel and the black Ni/NC product being calcinated in Ar atmosphere (c). The basic initial chemicals are citric acid and ethylene glycol and metal nitrates. NC means N doped carbon 112. Adapted from John Wiley and Sons publisher."

Fig 20

XRD profiles of Ni/NC (a), NiCo/NC (b) materials prepared by using gel-blowing method, HRTEM mage of NiCo/NC material (c), and catalytic behavior for hydrogen evolution reaction of NiCo/NC material 112. Adapted from John Wiley and Sons publisher."