Twelve methods of determining energy band gap $\left(E_g\right)$ of semiconductors using diffuse reflectance spectroscopy have been applied in investigations of sonochemically produced antimony sulfoiodide (SbSI) consisting of nanowires. It has been proved that the best method of determining $E_g$ is based on simultaneous fitting of many mechanisms of absorption to the spectral dependence of Kubelka–Munk function evaluated from the diffuse reflectance data. It allows determining the values of indirect forbidden $E_g$ , the Urbach energy, and the constant absorption/scattering of the examined semiconductor.

A novel sonochemical method for direct preparation of nanocrystalline antimony sulfoiodide (SbSI) has been established. The SbSI gel was synthesized using elemental Sb, S and I in the presence of ethanol under ultrasonic irradiation (35 kHz, 2 W/cm2) at 50 degrees C for 2 h. The products were characterized by using techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and optical diffuse reflection spectroscopy (DRS). The SEM and HRTEM investigations exhibit that the as-prepared samples are made up of large quantity nanowires with diameters of about 10-50 nm and lengths reaching up to several micrometers and single-crystalline in nature.

A novel piezoelectric paper based on antimony sulfoiodide (SbSI) nanowires is reported. The composite of tough sonochemically produced SbSI nanowires (with lateral dimensions 10–100 nm and length up to several micrometers) with very flexible cellulose leads to applicable, elastic material suitable to use in fabrication of, for example, piezoelectric nanogenerators. For mechanical energy harvesting, cellulose/SbSI nanocomposite may be used. Due to its high values of electromechanical coefficient (k₃₃ = 0.9) and piezoelectric coefficient (d₃₃ = 1 × 10⁻⁹ C/N), SbSI is a very attractive material for such devices. The preliminary investigations of a simple cellulose/SbSI nanogenerator for shock pressure (p = 3 MPa) and sound excitation (f = 175 Hz, L_p = 90 dB) allowed to determine its open circuit voltage 2.5 V and 24 mV, respectively. For a load resistance equal to source impedance (Z_S = 2.90(11) MΩ), maximum output power density (P_L = 41.5 nW/cm³ for 0.05-mm-thick sheet of this composite) of the cellulose/SbSI nanogenerator was observed. Cellulose/SbSI piezoelectric paper may also be useful to construct gas nanosensors and actuators.