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An environment friendly, economic and maneuverable hydrothermal method was proposed for fabrication of nitrogen and chlorine co-doped carbon quantum dots (N,Cl-CQDs). D-Glucosamine hydrochloride as the only precursor offered source of carbon, nitrogen and chlorine. As a consequent N,Cl-CQDs can emit blue luminescence and detect Fe${}^{3+}$ by fluorescence response with high selectivity and sensitivity. There is a linear semilogarithmic correlation between the quenching efficiency $F_0∕F$ and the concentration of Fe${}^{3+}$ with a detection limit of 0.167 $\mu$M. The N,Cl-CQDs exhibit a high quantum yield of 16.8% along with the fluorescence lifetime of 2.2ns. It is worth noting that the prepared N,Cl-CQDs show excellent biocompatibility and they are promising materials for sensing and biology.

The article introduces a mathematical model of the physical growth mechanism which is based on the relationships of the physical and geometrical parameters of the growing object, in particular its surface and volume. This growth mechanism works in cooperation with the biochemical and other growth factors. We use the growth equation, which mathematically describes this mechanism, and study its adequacy to real growth phenomena. The growth model very accurately fits experimental data on growth of Amoeba, Schizosaccharomyces pombe, E.coli. Study discovered a new growth suppression mechanism created by certain geometry of the growing object. This result was proved by experimental data. The existence of the growth suppression phenomenon confirms the real workings and universality of the growth mechanism and the adequacy of its mathematical description. The introduced equation is also applicable to the growth of multicellular organisms and tumors. Another important result is that the growth equation introduces mathematical characterization of geometrical forms that can biologically grow. The material is supported by software application, which is released to public domain.