Concluding Remarks and Perspectives

Since the pioneering papers of the 1980s, many functionalities have been explored concerning luminescent properties of sol-gel materials. This chapter has dealt with just a few of them involving lanthanide ions and organic dyes. 

Of course, advances are expected, merging important properties, for example, the utilization of NIR dyes in the harvesting of the solar energy aiming the enhancement of the efficiency of solar cells. Lanthanides upconversion is efficient and visible to the naked eye, provided that powerful excitation sources are used. Infrared light from the sun can hardly lead to observation of visible photons via upconversion. The efficiency of the process is indeed very low [130]. 

However, the utilization of NIR dyes could lead to dramatic increase in the efficiency, as shown in Ref. [131], where an organic NIR dye (IR-806) is used as 

Molecular thermometry, biophotonics imaging, chemical sensing, and new light sources are just some of the points mentioned here where the OIH strategy presents utmost importance and for which they will further contribute in the 

Authors acknowledge financial support from Brazihan agencies FAPESP, CNPq, and CAPES. Professor L.D. Carlos (University of Aveiro, Portugal) is acknowledged for helpful discussions. 

---

The outline of the chapter is the following. In Sec. 2, we give an overview of GH theory and various important limits, as well as an overview of its applications to assorted charge transfer reaction classes. In Sec. 3, we sketch a model development that is quite useful in comprehending the meaning of GH theory. Various MD simulation studies on reaction dynamics are described in Sec. 4. from the perspective of the preceding sections. Sec. 5 sketches some other related developments, while concluding remarks are offered in Sec. 6. 

At last, the concluding remarks will point out most important facts and future perspectives. 

---