Efficient Perovskite Solar Cells Based on Tin Oxide Nanocrystals with Difunctional Modification.

Tin oxide (SnO2 ) nanocrystals-based electron transport layer (ETL) has been widely used in perovskite solar cells due to its high charge mobility and suitable energy band alignment with perovskite, but the high surface trap density of SnO2 nanocrystals harms the electron transfer and collection within device. Here, an effective method to achieve a low trap density and high electron mobility ETL based on SnO2 nanocrystals by devising a difunctional additive of potassium trifluoroacetate (KTFA) is proposed. KTFA is added to the SnO2 nanocrystals solution, in which trifluoroacetate ions could effectively passivate the oxygen vacancies (OV ) in SnO2 nanocrystals through binding of TFA- and Sn4+ , thus reducing the traps of SnO2 nanocrystals to boost the electrons collection in the solar cell. Furthermore, the conduction band of SnO2 nanocrystals is shifted up by surface modification to close to that of perovskite, which facilitates electrons transfer because of the decreased energy barrier between ETL and perovskite layer. Benefiting from the decreased trap density and energy barrier, the perovskite solar cells exhibit a power conversion efficiency of 21.73% with negligible hysteresis.

Poly(γ-benzyl-L-glutamate)-PEG-alendronate multivalent nanoparticles for bone targeting.

Hydroxyapatite (HAP), a highly specific component of bone tissue, is the main target in order to impart osteotropicity. Bone targeted nanoparticles can increase the strength of the interaction with HAP through multivalency and thus constitute a valuable strategy in the therapeutics of skeletal diseases. PBLG10k-b-PEG6k-alendronate nanoparticles (~ 75 nm) were prepared by a simple nanoprecipitation method. The calcium affinity (KCa(+2)=1.8 × 10(4)M(-1)) of these nanoparticles was evaluated using isothermal titration calorimetry. The multivalent interaction with HAP surfaces (KHAP) was studied by fluorescence and was estimated to be 1.1 × 10(10)M(-1), which is more than 4000 times stronger than the reported monovalent interaction between alendronate and HAP surfaces. Molecular modeling suggests that the number of binding sites available at the HAP surface is in large excess than what is required for the whole surface coverage by alendronate decorated nanoparticles. The lower calcium affinity of these nanoparticles than for HAP allows calcium bound nanoparticles to interact with HAP, which yields a deeper understanding of bone targeted carriers and could potentially improve their bone targeting properties.