Regulating KBBF-like structures via a charge-assisted hydrogen-bonded framework to enable easily grown ultraviolet...

Area of Science:

• Materials Science
• Crystallography
• Nonlinear Optics

Background:

• Growing large, high-quality nonlinear optical (NLO) crystals is crucial for ultraviolet (UV) laser technologies.
• KBe$_{2}$BO$_{3}$F$_{2}$ (KBBF)-type crystals possess excellent NLO properties but are limited by layer separation, hindering the growth of application-scale single crystals.

Purpose of the Study:

• To develop a new strategy for synthesizing large, high-quality NLO crystals with improved structural stability.
• To overcome the limitations of layer separation in KBBF-type crystals for practical applications.

Main Methods:

• Incorporation of sulfanilamide and nitrate anions into a KBBF-like structure to create a 3D charge-assisted hydrogen-bonded framework.
• Synthesis of a novel UV NLO crystal, C$_{6}$H$_{9}$N$_{2}$SO$_{2}$·NO$_{3}$ (SAN), via aqueous solution evaporation at room temperature.

Main Results:

• The novel SAN crystal exhibits enhanced NLO properties, including a stronger second-harmonic generation (SHG) response (2.5 × KDP) and higher birefringence (0.112 at 546 nm) compared to KBBF.
• The 3D hydrogen-bonded network effectively suppresses layer exfoliation, enabling the direct growth of centimeter-scale SAN crystals (4.5 × 1 × 0.5 cm$^{3}$).

Conclusions:

• The study introduces a generalizable strategy of hydrogen-bond engineering within layered crystalline materials.
• This approach significantly improves crystal growth behavior and provides a pathway for developing advanced UV NLO materials.