Investigation of the photophysical properties of the HgI$_{2}$@mSiO$_{2}$ nanocomposite

The luminescent properties of a composite consisting of mesoporous silica and mercury diiodide nanoparticles formed in silica nanopores have been investigated. The formation of nanoparticles was carried out by evaporation of a HgI$_2$ solution introduced into the SiO$_2$ nanopores. It was found that photoluminescence of the HgI$_{2}$@mSiO$_{2}$ composite was due to emission of mercury diiodide, with the emission spectrum being significantly shifted towards shorter wavelengths with respect to the emission spectrum of bulk HgI$_2$ crystals. The shift of the HgI$_2$ emission spectrum to the short-wavelength side is explained by quantum-size effects in the electronic spectra of HgI$_2$ nanoparticles included in the composite. The significant width of the spectrum is explained by its inhomogeneous broadening due to the dependence of the band gap of the nanodots on their size $d$. The shape of the size distribution function of HgI$_2$ nanodots was estimated and it was shown that it was characterized by a rather narrow maximum at $d_{\mathrm{M}}$ = 2.2 nm, which is $\sim$ 2/3 of the diameter of the nanopores in the SiO$_2$ matrix ($\sim$ 3 nm).