3.1 Metal Oxides/Sulfides
45
etching/deposition, electrospinning methods, template-based methods, and laser
ablation, has been developed to create specific 1D nanomaterials (Niu et al. 2015).
Nevertheless, 1D nanostructures are only realizable for specific materials due to the
limited range of appropriate material properties for each synthetic method. Hence,
a general technique is required to manufacture nanowires, as well as nanotubes,
for a series of inorganic nanomaterials regardless of crystal orientation. Electrospinning methods have been used to manufacture a variety of conductive polymer
nanowires and inorganic nanowires. The feasible controlled pyrolysis method and
gradient-electrospinning method have been reported with low cost, extensive material diversity, high yield, and good repeatability, providing a promising method
to obtain tunable nanotubes for a series of inorganic materials and removing the
restriction of crystal growth orientation of different samples. Moreover, a variety
of tubular 1D nanomaterials have been synthesized based on this synthetic method
including single metal oxide nanotubes (MnO 2 , Co 3 O 4 , CuO and SnO 2 ), binary
metal oxides (LiCoO 2 , LiV 3 O 8 , NiCo 2 O 4 , and LiMn 2 O 4 ), and multi-element oxides
(LiNi 1/3 Co 1/3 Mn 1/3 O 2 , Na 0.7 Fe 0.7 Mn 0.3 O 2 , etc.). Transmission electron microscopy
(TEM) images of the mesoporous nanotubes are shown in Fig. 3.2k, l. The schematics
of the gradient electrospinning and controlled pyrolysis methods are shown in
Fig. 3.2j. Following a process of electrostatic spinning, the compound nanowires
are straightway placed into a furnace in air at 300 °C. Then, PVA decomposes simultaneously and quickly moves to the outside high molecular weight PVA layer without
taking away the desired inorganic materials, leaving inorganic materials in the central
zone. The inner inorganic materials and the outer PVA carbonize develop into typical
nanoparticles after high-temperature calcining under Ar atmosphere, forming pealike nanotubes. Accordingly, the electrostatic spinning method could lead to rapid
advancements in the progress of 1D nanostructures. Furthermore, these unique pealike and mesoporous nanotubes, which show outstanding electrochemical performance in supercapacitors, sodium-ion batteries, and lithium-ion batteries, owing to
their robust structural stability, high conductivity and large surface area hold great
promise not only in electrochemical energy storage devices but also in a number of
other frontiers.
3.2 Others
3.2.1 One-Dimensional Graphene
1D graphene nanomaterials are attracting significant attention on account of their
excellent thermal, mechanical, and electrical properties, which could lead to a series
of significant potential applications. Synthetic methods associated with making
1D carbon nanomaterials could consume a mass of energy and also comparative
complex, so a primary challenge is to develop efficient and simple processes to
produce them. Xu and co-workers successfully synthesized 1D carbon nanorods
45
etching/deposition, electrospinning methods, template-based methods, and laser
ablation, has been developed to create specific 1D nanomaterials (Niu et al. 2015).
Nevertheless, 1D nanostructures are only realizable for specific materials due to the
limited range of appropriate material properties for each synthetic method. Hence,
a general technique is required to manufacture nanowires, as well as nanotubes,
for a series of inorganic nanomaterials regardless of crystal orientation. Electrospinning methods have been used to manufacture a variety of conductive polymer
nanowires and inorganic nanowires. The feasible controlled pyrolysis method and
gradient-electrospinning method have been reported with low cost, extensive material diversity, high yield, and good repeatability, providing a promising method
to obtain tunable nanotubes for a series of inorganic materials and removing the
restriction of crystal growth orientation of different samples. Moreover, a variety
of tubular 1D nanomaterials have been synthesized based on this synthetic method
including single metal oxide nanotubes (MnO 2 , Co 3 O 4 , CuO and SnO 2 ), binary
metal oxides (LiCoO 2 , LiV 3 O 8 , NiCo 2 O 4 , and LiMn 2 O 4 ), and multi-element oxides
(LiNi 1/3 Co 1/3 Mn 1/3 O 2 , Na 0.7 Fe 0.7 Mn 0.3 O 2 , etc.). Transmission electron microscopy
(TEM) images of the mesoporous nanotubes are shown in Fig. 3.2k, l. The schematics
of the gradient electrospinning and controlled pyrolysis methods are shown in
Fig. 3.2j. Following a process of electrostatic spinning, the compound nanowires
are straightway placed into a furnace in air at 300 °C. Then, PVA decomposes simultaneously and quickly moves to the outside high molecular weight PVA layer without
taking away the desired inorganic materials, leaving inorganic materials in the central
zone. The inner inorganic materials and the outer PVA carbonize develop into typical
nanoparticles after high-temperature calcining under Ar atmosphere, forming pealike nanotubes. Accordingly, the electrostatic spinning method could lead to rapid
advancements in the progress of 1D nanostructures. Furthermore, these unique pealike and mesoporous nanotubes, which show outstanding electrochemical performance in supercapacitors, sodium-ion batteries, and lithium-ion batteries, owing to
their robust structural stability, high conductivity and large surface area hold great
promise not only in electrochemical energy storage devices but also in a number of
other frontiers.
3.2 Others
3.2.1 One-Dimensional Graphene
1D graphene nanomaterials are attracting significant attention on account of their
excellent thermal, mechanical, and electrical properties, which could lead to a series
of significant potential applications. Synthetic methods associated with making
1D carbon nanomaterials could consume a mass of energy and also comparative
complex, so a primary challenge is to develop efficient and simple processes to
produce them. Xu and co-workers successfully synthesized 1D carbon nanorods