Tailored structural regulation to achieve novel compounds with special properties is very attractive and important for functional material design. In this paper, CsIO 3 was selected as a maternal structure and three new derivatives, namely, CsIO 2 F 2 , Cs 3 (IO 2 F 2 ) 3 •H 2 O, and Cs(IO 2 F 2 ) 2 •H 5 O 2 , were successfully prepared by introducing different units (F − , H 2 O, H 5 O 2 + , and IO 2 F 2 −) under hydrothermal condition for the first time. Then, the structural transformations were schematically analyzed and the corresponding properties originated from ions introduction were investigated. Therein, noncentrosymmetric CsIO 3 and CsIO 2 F 2 exhibit good nonlinear optical properties with large second-harmonic generation (SHG) effects (15 × and 3 × KH 2 PO 4 ), wide band gaps (4.2 and 4.5 eV), wide transmittance ranges (∼0.27−5.5 μm), and high laser damage thresholds (15 × and 20 × AgGaS 2 , respectively), which shows that they are potential nonlinear optical materials in near-ultraviolet to mid-infrared. To further analyze the structure−properties relationship, the first-principles calculations are applied to explore the origins of the optical properties, such as birefringences and SHG responses. Moreover, the protonated (H 5 O 2 ) + cations in Cs(IO 2 F 2 ) 2 •H 5 O 2 imply that it may feature enhanced conductivity, which was tentatively verified by the resistivity tests via the conventional dc four-probe method. The study case of structural regulation realized by ions introduction in this work may give a feasible guidance for functional materials design.

A new alkali metal iodate, K 2 Na(IO 3 ) 2 (I 3 O 8 ), has been synthesized using the mild hydrothermal method, which is the first example of noncentrosymmetric iodate containing isolated [IO 3 ] − and [I 3 O 8 ] − groups. To the best of our knowledge, it exhibits the largest second harmonic generation response among the iodates with two types of isolated I−O groups (7.6 × KH 2 PO 4 (KDP) @1064 nm). It also possesses a moderate birefringence (Δn) of 0.055 at 1064 nm for achieving its phase matching and a wide band gap (3.83 eV) for obtaining a high laser damage threshold, which assures that it possesses a high laser-induced damage threshold (LDT, 13 × AgGaS 2 ). These results indicate that it is a good candidate for nonlinear optical applications.

What is the most significant result of this study?In recent years, extensive research and continuous development have been presented on second-order nonlinear optical (NLO) crystal materials due to their potential applications in telecommunications, optical information processing, and optical data storage. In this study,t he first rare-earth iodate fluoride, Ce(IO 3 ) 2 F 2 ·H 2 O, has been synthesized, The results show that Ce(IO 3 ) 2 F 2 ·H 2 Oi sa ni odate fluoride with an ew structure and has potential applications in the field of nonlinear optics. What was the inspiration for this cover design?For us, the first encounter with geometry is on the blackboard at school. From that time on, we have been fascinated by the beauty of symmetry.C oincidentally,g eometric structures also inspire many chemists and play af undamental role in determining new ideas. Thus, this cover combines the elements of laser frequency doubling using an NLO crystal, the structure of Ce(IO 3 ) 2 F 2 ·H 2 Oa nd geometry to create a"surrealistic world".What other topics are you working on at the moment?We are currently focusing on the investigation of new photoelectric functional crystals, such as NLO and birefringent crystals. Especially,w et ry to design new compounds with excellent optical properties by the introduction of fluorine into, for example, iodates, borates, and phosphates. Extensive experiments prove that this is an effective design strategy to synthesize new materials.Invited for the cover of thisi ssuei sS hilie Pan and co-workers at Xinjiang Technical Institute of Physics and Chemistry,C hinese Academy of Sciences. The first rare-earth iodate fluoride, Ce(IO 3 ) 2 F 2 ·H 2 O, has beens ynthesized, which produces al arge second harmonic generation response. Read the full text of the article at