|Upconverting Nanoparticles (UCNPs) and Composite Materials|
|ㆍ작성일: 2017-12-21 (목) 20:16||ㆍ조회: 188|
Upconverting Nanoparticles (UCNPs) and Composite Materials
Photoluminescence processing normally involves absorbing light at one wavelength while emitting light at another. There are two kinds of mechanisms in the photoluminescence process: linear down-conversion process and nonlinear up-conversion process. Typical down-conversion photoluminescence normally absorbs one high energy short wavelength photon and emits a low energy long wavelength photon. The up-conversion process is a nonlinear optics process that absorbs low energy light, usually near infrared (NIR) or infrared (IR), converts it to higher energies, visible, or ultraviolet, via multiple absorptions or energy transfer processes. The up-conversion process was observed in core-shell nanoparticles, transition metal, lanthanide and actinide ions doped solid state host. Among them, the highest efficiencies are found in lanthanide doped fluoride materials.
Figure 1. Comparison of FL emission of typical organic dye, CdSe/ZnS QDs, and UCNPs downconversion (FWHM: full width at half maximum; FW10%M: full width at 10% maximum).
Figure 2.High resolution transmission electron microscopy (HRTEM) images of UCNPs in Mesolight.
Preparation of high quality (mono-dispersed, high upconversion efficiency, and long term storage stability) UCNPs is very challenging. The most developed solvothermal synthesis has good size control and monodispersion for UCNPs. However, it involves the use of trifluoroacetic acid (TFA) which is a very volatile, corrosive, and extremely hazardous agent. The decomposition of the metal trifluoroacetates also produces various hazard fluorinated chemicals and results in low up-conversion efficiency. Another issue is the multiple emission peaks of UCNPs. For example, NaYF4:Er/Yb and NaYF4:Tm/Yb UCNPs typically exhibit multiple combined emissions generated from different transition states, e.g., NaYF4:Er/Yb UCNPs typically exhibits green (550 nm) and red (655 nm) emissions.
● Blue-emitting UCNPs (emission peak at 465 nm) (Figure 3)
Figure 3.Upconverting emission spectrum of blue-emitting high color purity UCNPs (insert: optical picture of the emission) (excitation: 980 nm)
● Green-emitting UCNPs (emission peak at 550nm) (Figure 4)
Figure 4.Upconverting emission spectrum of green-emitting high color purity UCNPs (insert: optical picture of the emission) (excitation: 980 nm)
● Red-emitting UCNPs (emission peak at 650 nm) (Figure 5)
Figure 5.Upconverting emission spectrum of red-emitting high color purity UCNPs (insert: optical picture of the emission) (excitation: 980 nm)
NIR-emitting UCNPs (emission peak at 800 nm) (Figure 6)
Figure 6.Upconverting emission spectrum of NIR-emitting (800 nm) high color purity UCNPs (excitation: 980 nm)
These UCNPs products dispersed in organic solvent feature high up-converting efficiency, high light output, high monodispersity, high solution dispersity, tunable size from 6-100 nm, exceptional narrow emission bandwidth, and also exception emission color purity (Figures 2-6).
Figure 7. Green-emitting UCNPs in aqueous solution: (left) transparent UCNPs solution and (right) bright green emission when excited with a 980 nm diode laser.
Figure 8. Six UCNPs/polymer composite materials transparent in the visible range (left) and their corresponding green upconverting emissions excited with a 980 nm diode laser (right).
제조사 : www.mesolight.cc