Recent Developments on Molten Salt Synthesis of Inorganic Nanomaterials: A Review

Abstract

A wide range of inorganic nanomaterials with many fascinating properties and application potentials in widespread fields may be synthesized by wet chemical synthetic routes. To achieve scientific and commercial viability of nanomaterials with uniformity and scalability, it is necessary to develop efficient and cost-effective, preferably sustainable, methods. The molten salt synthesis (MSS) method is one such bottom-up technique to fabricate a wide variety of inorganic nanomaterials with tunable size, morphology, and surface characteristics. It is also environmentally friendly, cost-effective, simple to operate, easy to scale, and generalizable, etc. This review gives a critical overview on this emerging and rapidly developing method for making defect free nanomaterials in well-defined texture, surface, and morphology at a relatively low formation temperature. We have discussed its different aspects, including the role of molten salts, the choice of molten salts, the electrochemical aspects, some advanced modifications of the conventional MSS technique, and their implications. To show the most recent development on MSS synthesized inorganic nanomaterials, this review only encompasses the studies reported over the last six years (2015−2020). We have summarized technologically important and emerging families of inorganic nanomaterials such as metal oxides, fluorides, nitrides, silicides, chalcogenides, oxohalides, borides, and carbides. Finally, a few perspectives for the MSS method are highlighted. It is expected that this review will further attract scientists to explore the MSS method in making size-and shape-tunable nanomaterials.

Up- and Down-Convertible LaF3:Yb,Er Nanocrystals with a Broad Emission Window from 350 nm to 2.8 μm: Implications for Lighting Applications

“…To prepare pure LaF 3 NCs and derivatives doped with y mol % Yb 3+ (y = 5, 7, 10, and 20) and 1.0 mol % Er 3+ , a MSS method was used, as shown in Scheme 1. 21 The details of the methods and thermal annealing are given in Supporting Information S1 and S2, respectively. The obtained pure LaF 3 NCs were designated as LF.…”

Highly Polymerized Wine-Red Carbon Nitride to Enhance Photoelectrochemical Water Splitting Performance of Hematite

“…The photoelectrochemical (PEC) water splitting strategy to convert solar energy into fuels, such as hydrogen, is considered one of the most promising methods to resolve the global energy/environmental crisis . In the past few years, many endeavors have been made to develop efficient and environmentally friendly semiconductor photoelectrodes. , Polymeric carbon nitride (p-C 3 N 4 ), as an organic semiconductor photocatalyst, has attracted rising attention in photocatalytic and photoelectrochemical water splitting due to its suitable band gap of ∼2.7 eV, facile adjustment of electronic structure, earth abundance, nontoxicity, and chemical and thermal stability . Generally, bulk carbon nitride is synthesized by direct thermal polymerization of precursors containing carbon and nitrogen, for instance, melamine, , dicyandiamide, , and thiourea .…”

“…2,3 Polymeric carbon nitride (p-C 3 N 4 ), as an organic semiconductor photocatalyst, has attracted rising attention in photocatalytic and photoelectrochemical water splitting due to its suitable band gap of ∼2.7 eV, facile adjustment of electronic structure, earth abundance, nontoxicity, and chemical and thermal stability. 4 Generally, bulk carbon nitride is synthesized by direct thermal polymerization of precursors containing carbon and nitrogen, for instance, melamine, 5,6 dicyandiamide, 7,8 and thiourea. 9 However, bulk carbon nitride usually suffers from limited visible-light absorption due to its wide band gap 10 and incomplete polymerization with residual amino and imino groups serving as recombination centers for photogenerated electron−holes, 11 resulting in very poor photocatalytic activity.…”

Light Harvesting from Oxygen Vacancies and A- and B-Site Dopants in CaSnO3 Perovskite through Efficient Photon Utilization and Local Site Engineering

“…Design of efficient optoelectronic devices, light -emitting diodes, scintillators, and so forth, requires a very thorough analysis of materials particularly regarding structure, defects, doping efficiency, dopant local structure, and so forth. − This becomes much more important in structurally flexible oxides such as ABO 3 perovskites. Perovskites are considered one of the most investigated materials for a variety of applications owing to their unique electronic, optical, magnetic, catalytic, and ferroelectric properties. ,, Among perovskites, CaSnO 3 (CSO), a high band gap semiconductor with a band gap of ∼4.7 eV is considered a highly diverse oxide owing to its unique structure, properties, and multifunctional applications. These included optoelectronics, catalysis, sensors, photodetectors, phosphors, lithium-ion batteries, and so forth. ,− Defects such as antisites, Schottky, oxygen vacancies (OVs), and so forth are abundantly present in CSO and are reported to have significant influence on its optical, catalytic, magnetic, and electrical properties. − These defects can also lead to interesting photoluminescence properties in CSO as well, which is an extremely important area of research in these days for designing dopant- and lattice strain-free phosphors .…”

“…Perovskites are considered one of the most investigated materials for a variety of applications owing to their unique electronic, optical, magnetic, catalytic, and ferroelectric properties. 3,5,6 Among perovskites, CaSnO 3 (CSO), a high band gap semiconductor with a band gap of ∼4.7 eV 7 is considered a highly diverse oxide owing to its unique structure, properties, and multifunctional applications. These included optoelectronics, catalysis, sensors, photodetectors, phosphors, lithium-ion batteries, and so forth.…”