We synthetized a series of strontium-substituted submicron bioactive glasses spheres (Sr-SBG, SiO 2 -P 2 O 5 -CaO-SrO) in which strontium was substituted for calcium on a mole percentage basis, then investigated the effect of strontium-substituted amount on morphologies, physicochemical properties, apatite-forming bioactivity of SBG and evaluated the proliferation, differentiation and mineralization of Sr-SBG with different strontium substitution amounts by co-cultured with human dental pulp cells (HDPCs). Results showed that Sr-SBG with different strontium substitution amounts were successfully fabricated and substituting different strontium amounts did not affect the morphology and particle size of SBG. All the Sr-SBG possessed good apatite-forming ability, but substituting a certain amount of strontium for calcium would weaken the apatite-forming ability of SBG. Additionally, all the Sr-SBG extractions promoted proliferation, early odontogenic differentiation and mineralization of HDPCs, however, the cell proliferation, differentiation and mineralization abilities would be reduced when the substituted amount of strontium was excess (15 mol%). This study suggests that Sr-SBG with moderate strontium substitution amounts can be used as a more promising biomaterial for dental repair.
Organic–inorganic hybrid perovskite solar cells (PSCs) have become a research hotspot because of their excellent power conversion efficiency (PCE), but the presence of toxic lead (Pb) in perovskite films has significantly limited their commercial applications. In this study, using a TiO2 nanorod array (TNRA) as the electron transport layer, strontium chloride (SrCl2) was chosen to fabricate lead-less PSCs in air (relative humidity, RH = 50%) by a simple two-step spin-coating method. The influence of introduced strontium (Sr) on the perovskite films and cell properties was systematically investigated by various characterization methods. With an increasing Sr substitution amount from 0 to 15 mol %, the formed perovskite films with a compact structure and large crystalline size essentially remained invariable, while the amount of residual PbI2 was reduced, which is beneficial for the cell performance. An optimal PCE of 16.08% (average PCE = 15.37%) was obtained for the 5 mol % Sr-substituted PSCs because of the enhanced charge extraction from the perovskite films to the TNRAs and the suppressed charge recombination in the PSCs. Both the humidity and thermal stability of the Sr-substituted PSCs were improved. More importantly, the 15 mol % Sr-substituted PSCs still exhibited a PCE of 15.09% in air (RH = 50%), maintaining 99% of the cell efficiency of the pristine (0 mol % Sr) PSC (15.27%), suggesting that the structure of TNRAs is suitable for the synthesis of high-performance Sr-substituted lead-less PSCs.
Cubic phase CsPbI3 quantum dots (α-CsPbI3 QDs) as a newly emerging type of semiconducting QDs hold tremendous promise for fundamental research and optoelectronic device applications. However, stable and sub-5 nm-sized α-CsPbI3 QDs have rarely been demonstrated so far due to their highly labile ionic structure and low phase stability. Here, we report a novel strontium-substitution along with iodide passivation strategy to stabilize the cubic phase of CsPbI3, achieving the facile synthesis of α-CsPbI3 QDs with a series of controllable sizes down to sub-5 nm. We demonstrate that the incorporation of strontium ions can significantly increase the formation energies of α-CsPbI3 QDs and hence reduce the structure distortion to stabilize the cubic phase at the few-nanometer size. The size ranging from 15 down to sub-5 nm of as-prepared stable α-CsPbI3 QDs allowed us to investigate their unique size-dependent optical properties. Strikingly, the few-nanometer-sized α-CsPbI3 QDs turned out to retain high photoluminescence and highly close packing in solid state thin films, and the fabricated red light emitting diodes exhibited high brightness (1250 cd m–2 at 9.2 V) and good operational stability (L50 > 2 h driven by 6 V). The developed cation-substitution strategy will provide an alternative method to prepare uniform and finely size-controlled colloidal lead halide perovskite QDs for various optoelectronic applications.
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