An overview of general classification scheme, medicinal importance and crystal structure analysis with emphasis on the role of hydrogen bonding in some alkaloids is presented in this paper. The article is based on a general kind of survey while crystallographic analysis and role of hydrogen bonding are limited to only those alkaloids whose three-dimensional structure has been reported by us. The C–H…O hydrogen bonding in the solid state in alkaloids has been found to be predominant and this observation makes the role of hydrogen bonding in organic molecular assemblies very important.

The synthesis, X-ray structure and role of intermolecular interactions have been studied in case of 1,3-diphenyl-urea, owing to its medicinal importance. The compound crystallizes in orthorhombic crystal system (space group, 𝑃𝑛𝑎2₁) with unit cell parameters, 𝑎 = 9.118(3), 𝑏 = 10.558(2), 𝑐 = 11.780(3) Å and 𝑍 = 4. The structure has been solved by direct methods and refined to a final 𝑅-value of 0.0316. The oxygen atom of the carbonyl group is responsible for the existence of two N–H…O intermolecular interactions.

A series of ZnO nanophosphors doped with different concentrations of Mg ($x$ = 0–0.05) were synthesized by combustion route using urea as the fuel. The final powdered products were well characterized by using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), transmission electron microscopy (TEM), UV–visible spectroscopy (UV–Vis) and photoluminescence (PL) characterization techniques. The powder XRD patterns of the formed product shows hexagonal phase. Scherrer equation was employed to calculate the average crystallite size and was found to be in the range of 30–50 nm. XRF study confirmed the chemical analysis of the samples. The agglomerated morphology of the samples was established by the TEM studies. Band gap calculations weredone with UV–visible spectroscopy. PL properties of undoped and ZnO:Mg ($x$ = 0–0.05) using 325 nm excitation source were studied to investigate the possibility of its use for display devices. The emission spectra consisted of an excitonic band edge emission and visible emission at 500 nm corresponding to blue light. The CIE colour coordinates also correspond to the bluish-white emission. The obtained results indicated that the synthesized phosphor can be explored as auseful material for display applications.

In this study, LiZr$_2$(PO$_4$)$_3$ nanophosphors with varying concentrations of Sm$^{3+}$ (0.25 ${\le}$x${\le}$ 3.0 mol%) utilizing urea as an organic fuel were synthesized via combustion method. Here, we investigated the fluctuations in the various parameters of lattice and verified the phase (trigonal) examined by the powder X-ray diffraction system. The elemental analysis was done with energy dispersive X-ray spectroscopy and the morphology was obtained using scanning electron microscope as well as transmission electron microscope. The electrical and optical characteristics of nanophosphor were determined using UV–vis spectroscopy and photoluminescence (PL) spectroscopy. The bandgap adjustment in the region of 4.065–4.462 eV was achieved by doping LiZr$_2$(PO$_4$)$_3$ with Sm$^{3+}$ from 0.25 to 3 mol%. PL characteristics of undoped and Li$_{(1–x)}$Zr$_2$(PO$_4$)$_3$:xSm$^{3+}$ (x = 1.5 mol%) were explored using a 405 nm excitation source to look into the viability of employing it for displays. In the visible spectrum, the PL spectra exhibit three distinct peaks at 566, 601 and 649 nm. The findings showed that synthesized phosphor might be investigated as a potential material forvarious display technology.