Synthesis, nanocrystalline morphology, lattice dynamics and nonlinear optics of mesoporous SiO2&LiNbO3 nanocomposite

• Published in: Scientific reports Vol. 14; no. 1; p. 24237
• Main Authors: Shchur, Yaroslav, Karout, Houda El, Sahraoui, Bouchta, Andrushchak, Anatoliy, Beltramo, Guillermo, Pustovyi, Denys, Vitusevich, Svetlana, Huber, Patrick, Kityk, Andriy V.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16-10-2024; Nature Publishing Group
• Subjects: 639/301/119; 639/301/357; 639/925/357; Crystallization; Crystals; Disease transmission; High temperature; Humanities and Social Sciences; Isotropy; Lithium; Membranes; Microscopy; Morphology; multidisciplinary; Nanocomposites; Nanocrystals; Niobium; Optics; Science; Science (multidisciplinary); Silica; Silicon dioxide; Transmission electron microscopy; X-ray diffraction
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-024-75686-6

We demonstrate a hybrid nanocomposite combining mesoporous silica,
p
SiO
2
, as a host medium and guest lithium niobate
LiNbO
3
nanocrystals embedded into tubular silica nanochannels by calcination of the precursor mixed solution of lithium and niobium salts. High-resolution transmission electron microscopy, X-ray diffraction and Raman scattering techniques reveal trigonal
LiNbO
3
nanocrystals within the
p
SiO
2
nanochannels, indicating their random texture morphology. Annealing at high temperatures ( 950
∘
C) during calcination also leads to partial crystallization of the
p
SiO
2
matrix with the formation of trigonal
α
-
SiO
2
nanocrystals. The Raman microscopy analysis of the
p
SiO
2
:
LiNbO
3
nanocomposite reveals three structural crystalline phases,
α
-
SiO
2
,
LiNbO
3
and a mixed phase which involves the
α
-
SiO
2
phase of host membrane and
LiNbO
3
nanocrystals embedded into the membrane. The finite size of the
LiNbO
3
nanocrystals results in specific features of the LO-TO phonon frequency splitting, which are investigated by Raman microscopy. In the transmission geometry, the second harmonic generation emission exhibits no Maker fringes and is characterized by a broad angular diagram of diffusely scattered light. The second harmonic generation response is independent of the polarization direction of the incident pump light, thus indicating a spatial isotropy of the nonlinear optical conversion in the
p
SiO
2
:
LiNbO
3
composite, consistent with the randomly oriented textural morphology of the deposited
LiNbO
3
nanocrystals. The contribution of the guest
LiNbO
3
nanocrystals to the second harmonic generation effect was found to be strongly dominant compared to the partially crystallized host
p
SiO
2
matrix. The nanocomposite
p
SiO
2
:
LiNbO
3
membrane, set in the 90
∘
nonlinear optical geometry, shows unusually high diffusely transmitted second harmonic generation light (back-reflected emission), apparently supported by internal light reflection from the tubular nanochannel network. Despite the fundamental interest, the revealed anomalous back-reflected second harmonic generation emission from
p
SiO
2
:
LiNbO
3
nanocomposite membranes expands the prospects for their photonic and nonlinear optical applications.