Surface Ligand Chemistry on Quaternary Ag(InxGa1-x)S2 Semiconductor Quantum Dots for Improving Photoluminescence Properties

Ternary and quaternary semiconductor quantum dots (QDs) are candidates for cadmium-free alternatives. Among these, semiconductors containing elements from groups 11, 13, and 16 (i.e., I–III–VI2) are attracting increasing attention since...

Synergetic effect of the surface ligand and SiO2 driven photoluminescence stabilization of the CH3NH3PbBr3 perovskite magic-sized clusters

Zero-dimensional Perovskite Magic-size Clusters play crucial roles in understanding and controlling nucleation and growth of semiconductor nanoparticles. However, their metastability behavior is a critical hindrance for reliable characterizations. Here, we report the first demonstration of using an excess amount of surface ligand and SiO2 as novel passivation for synthesizing the magic-sized clusters (MSCs) by the Ligand-assisted reprecipitation method. A synergetic effect between an excessed surface ligand and SiO2 inhibits the protonation and deprotonation reaction between amine-based and acid-based ligand, leading to enhanced PL stability. The obtained CH3NH3PbBr3 PMSCs/SiO2 retain 70% of its initial emission intensity in ambient conditions for 20 days. This passivation approach opens an entirely new avenue for the reliable characterizations of CH3NH3PbBr3 PMSCs, which will significantly broaden their application for understanding and controlling nucleation and growth of semiconductor nanoparticles.

Nitroreductase-Induced Aggregation of Gold Nanoparticles for “Off–On” Photoacoustic Imaging of Tumor Hypoxia

Hypoxia is an important phenomenon due to insufficient oxygen supply in tumor tissue, and nitroreductase (NTR) is a characteristic enzyme used for evaluating hypoxia level in tumors. In this work, we designed a smart gold nanoparticle (AuNPs), modified by 16-mercaptoundecanoic acid (MHDA) and hypoxia-responsive 11-(2-nitro-1H-imidazol-1-yl)undecane-1-thiol (NI) ligand, that responds to the hypoxic environment in tumor sites. With proper surface ligand composition, the responsive nanoprobe exhibited aggregation through the bioreduction of the nitro group on NI ligands under hypoxic conditions and the UV-vis absorption peak maximum would shift to 630 nm from 530 nm, which acts as an “off–on” contrast agent for tumor hypoxic photoacoustic (PA) imaging. In vitro and in vivo experiments revealed that AuNPs@MHDA/NO2 exhibited an enhanced PA signal in hypoxic conditions. This study demonstrates the potential of hypoxia-responsive AuNPs as novel and sensitive diagnostic agents, which lays a firm foundation for precise cancer treatment in the future.

Physical Origin of Dual-Emission of Au–Ag Bimetallic Nanoclusters

On the origin of photoluminescence of noble metal NCs, there are always hot debates: metal-centered quantum-size confinement effect VS ligand-centered surface state mechanism. Herein, we provided solid evidence that structural water molecules (SWs) confined in the nanocavity formed by surface-protective-ligand packing on the metal NCs are the real luminescent emitters of Au-Ag bimetal NCs. The Ag cation mediated Au-Ag bimetal NCs exhibit the unique pH-dependent dual-emission characteristic with larger Stokes shift up to 200 nm, which could be used as potential ratiometric nanosensors for pH detection. Our results provide a completely new insight on the understanding of the origin of photoluminescence of metal NCs, which elucidates the abnormal PL emission phenomena, including solvent effect, pH-dependent behavior, surface ligand effect, multiple emitter centers, and large-Stoke’s shift.