other processing parameters, such as precursor concentration, solvent composition,
heating rate, and reaction time. This approach has been extended as a common route
to yield a multitude of high-quality, monodispersed RENPs based on a myriad of
hosts including NaYF 4 , NaGdF 4 , CaF 2 , etc.
Hydrothermal or solvothermal synthesis is a versatile synthesis technique that
involves reacting precursors in aqueous or nonaqueous solvent media, respectively,
at elevated temperatures (25
C or greater) and pressures (1 atm or greater) to
crystallize materials over a broad range of particle sizes directly from solution in a
single process step [51–58]. Specialized reaction vessels known as autoclaves are
usually required for the solvothermal reaction, in which a high pressure and temperature environment are generated. Generally, highly crystalline phases are prepared at much lower temperatures with higher yields than thermal decomposition
method for the synthesis of RENPs. Besides selecting suitable precursors, solvents,
reaction conditions (e.g., duration, temperature, pressure), the phase purity, particle
size, and morphology of RENPS are tailored with the addition of surfactants.
3.3 Application In Vivo
Highly monodisperse RENPs are typically formed in high-boiling organic solvents.
The poor aqueous solubility of surfactant on the surface of the nanoparticles prevents
subsequent functionalization for biomedical applications. Surface modification is
thus crucial for improving the dispersion of RENPs in water. For example, by
encapsulating RENPs with FDA-approved albumin, Naczynski et al. successfully
Fig. 11 Schematics of
typical NIR-II emission of
energy conversion processes
for RENP materials: (a)
down-conversion (DC) and
(b) down-shifting (DS)
Table 1 Comparison of synthesis parameters and properties of products for both thermal decomposition and solvo(hydro)thermal methods
Category
Thermal decomposition
Solvo(hydro)thermal
Temperature
250–330
C
100–220
C
Time
2 h
48 h
Yield
Up to 1 g
Up to 10 g
Size
Narrow
Broad
Morphology
Sphere, rod, polyhedron
Sphere, rod, polyhedron, spindle
Solubility
Hydrophobic
Hydrophilic/hydrophobic
Advancements of Second Near-Infrared Biological Window Fluorophores:. . .
97
heating rate, and reaction time. This approach has been extended as a common route
to yield a multitude of high-quality, monodispersed RENPs based on a myriad of
hosts including NaYF 4 , NaGdF 4 , CaF 2 , etc.
Hydrothermal or solvothermal synthesis is a versatile synthesis technique that
involves reacting precursors in aqueous or nonaqueous solvent media, respectively,
at elevated temperatures (25
C or greater) and pressures (1 atm or greater) to
crystallize materials over a broad range of particle sizes directly from solution in a
single process step [51–58]. Specialized reaction vessels known as autoclaves are
usually required for the solvothermal reaction, in which a high pressure and temperature environment are generated. Generally, highly crystalline phases are prepared at much lower temperatures with higher yields than thermal decomposition
method for the synthesis of RENPs. Besides selecting suitable precursors, solvents,
reaction conditions (e.g., duration, temperature, pressure), the phase purity, particle
size, and morphology of RENPS are tailored with the addition of surfactants.
3.3 Application In Vivo
Highly monodisperse RENPs are typically formed in high-boiling organic solvents.
The poor aqueous solubility of surfactant on the surface of the nanoparticles prevents
subsequent functionalization for biomedical applications. Surface modification is
thus crucial for improving the dispersion of RENPs in water. For example, by
encapsulating RENPs with FDA-approved albumin, Naczynski et al. successfully
Fig. 11 Schematics of
typical NIR-II emission of
energy conversion processes
for RENP materials: (a)
down-conversion (DC) and
(b) down-shifting (DS)
Table 1 Comparison of synthesis parameters and properties of products for both thermal decomposition and solvo(hydro)thermal methods
Category
Thermal decomposition
Solvo(hydro)thermal
Temperature
250–330
C
100–220
C
Time
2 h
48 h
Yield
Up to 1 g
Up to 10 g
Size
Narrow
Broad
Morphology
Sphere, rod, polyhedron
Sphere, rod, polyhedron, spindle
Solubility
Hydrophobic
Hydrophilic/hydrophobic
Advancements of Second Near-Infrared Biological Window Fluorophores:. . .
97