Shell-Thickness-Dependent Biexciton Lifetime in Type I and Quasi-Type II CdSe@CdS Core/Shell Quantum Dots

Suppression of Auger recombination in colloidal quantum dots (QDs) is important for their many applications, ranging from biological tagging, QD lasing, to solar energy conversion. Although it has been reported that the biexciton Auger recombination time of core/shell QDs can be significantly prolonged compared to core-only QDs, a systematic investigation of their dependence on the shell thickness is lacking. In this work, using CdSe@CdS core/shell QDs as a model system, we investigated the shell thickness dependence of biexciton lifetimes in both type I and quasi-type II QDs, prepared using large and small core sizes, respectively. We observe a strong increase of biexciton lifetime with the shell thickness and a larger saturation volume in quasi-type II CdSe@CdS QDs, compared to type I CdSe@CdS QDs. These trends can be attributed to the different thickness dependences of electron–hole wave function overlaps in these materials, which reflect their different extents of conduction band electron delocalization. Our findings provide further insight for rational design of core/shell QDs with suppressed Auger recombination rates

Ultrafast Interfacial Electron and Hole Transfer from CsPbBr₃ Perovskite Quantum Dots

Recently reported colloidal lead halide perovskite quantum dots (QDs) with tunable photoluminescence (PL) wavelengths covering the whole visible spectrum and exceptionally high PL quantum yields (QYs, 50–90%) constitute a new family of functional materials with potential applications in light-harvesting and -emitting devices. By transient absorption spectroscopy, we show that the high PL QYs (∼79%) can be attributed to negligible electron or hole trapping pathways in CsPbBr₃ QDs: ∼94% of lowest excitonic states decayed with a single-exponential time constant of 4.5 ± 0.2 ns. Furthermore, excitons in CsPbBr₃ QDs can be efficiently dissociated in the presence of electron or hole acceptors. The half-lives of electron transfer (ET) to benzoquinone and subsequent charge recombination are 65 ± 5 ps and 2.6 ± 0.4 ns, respectively. The half-lives for hole transfer (HT) to phenothiazine and the subsequent charge recombination are 49 ± 6 ps and 1.0 ± 0.2 ns, respectively. The lack of electron and hole traps and fast interfacial ET and HT rates are key properties that may enable the development of efficient lead halide perovskite QDs-based light-harvesting and -emitting devices

Matrix metalloproteinse 9 (MMP-9) expression profiles in each group.

<p>red, MMP9–positive; blue, DAPI-positive cells. (magnification:x20; scale bars: 50μm).</p

Fluorescence Imaging of Diabetic Cataract-Associated Lipid Droplets in Living Cells and Patient-Derived Tissues

Diabetic cataract (DC) surgery carries risks such as slow wound healing, macular edema, and progression of retinopathy and is faced with a deficiency of effective drugs. In this context, we proposed a protocol to evaluate the drug’s efficacy using lipid droplets (LDs) as the marker. For this purpose, a fluorescent probe PTZ-LD for LDs detection is developed based on the phenothiazine unit. The probe displays polarity-dependent emission variations, i.e., lower polarity leading to stronger intensity. Especially, the probe exhibits photostability superior to that of Nile Red, a commercial LDs staining dye. Using the probe, the formation of LDs in DC-modeled human lens epithelial (HLE) cells is validated, and the interplay of LDs–LDs and LDs-others are investigated. Unexpectedly, lipid transfer between LDs is visualized. Moreover, the therapeutic efficacy of various drugs in DC-modeled HLE cells is assessed. Ultimately, more LDs were found in lens epithelial tissues from DC patients than in cataract tissues for the first time. We anticipate that this work can attract more attention to the important roles of LDs during DC progression

ICES Induced Corneal Epithelial Destruction.

<p>Corneal epithelial damage assessment by standard corneal fluorescein staining scores in ICES groups (E), the scopolamine-treated group (SCOP) and normal control group (N). *P < 0.05 versus the normal group (N).</p

Inflammatory cells infiltration of the Lacrimal Gland.

<p>A-E, immunostained for CD4(A), CD8(B), CD103(C), CD11b(D), CD45(E) in the lacrimal glands sections. F, Cell counts in mouse lacrimal glands stained by immunohistochemistry for CD4, CD8, CD103, CD11b, CD45 sections in the normal group (N), the scopolamine-treated group (SCOP), and after desiccating stress in ICES for 1 week, 2 week, 4 week and 6 week (E1,E2,E4,E6). # P < 0.01 versus the scopolamine-treated group (SCOP), * P<0.05 versus the normal group(N) (Mann-Whitney U test). Original magnification:x20；scale bars = 50 μm. Experiments were repeated three times with two mice per group per experiment.</p

Electron microscopic findings of the lacrimal gland acinus.

<p>A, Secretory vesicle (SV) accumulation in the normal group(N), Scale bars = 1um. Atrophic SVs in the scopolamine-treated group (SCOP).Excessive accumulation of SVs in the 1-week in the E group (E1).Excessive accumulation of SVs in the 2-week group (E2). Excessive accumulation of SVs in the 4-week group (E4).Excessive accumulation of SVs in the 6-week group (E6). B: SV diameter. Total number of vesicles examined/group: 159/N group，254/SCOP group, 249/E1 group, 341/E2 group, 302/E4 group and 485/E6 group (Mann-Whitney U test). C: Percent SV area per acinus. Total number of acini examined/group: 148/N group ，177/SCOP group, 223/E1 group, 270/E2 group, 339/E4 group and 549/E6 group (Mann-Whitney U test) # P<0.001 versus the SCOP group, ** p<0.001 versus the normal group(N).~ P<0.001 versus the the E2 group. Original magnification: X10000. Hollow arrow, Ductal lumen; Arrows, Nuclei; Triangle, SV.</p

Primers used for quantitative RT-PCR.

<p>Primers used for quantitative RT-PCR.</p

ICES Stimulates Inflammatory Cytokine Production in the Conjunctiva and Lacrimal Gland.

<p>A, Real-time PCR for the mRNA expression of IL-17, IL-23, IL-6, IL-1β, TNF-α, IFN-γ, TGF-β2 in the conjunctiva of normal group(Horizontal line), the scopolamine-treated group (SCOP), and after desiccating stress in ICES for 1 week,2week,4 week and 6week (E1,E2,E4,E6). B, mRNA transcript levels of IL-17,IL-23,IL-6,IL-1β, TNF-α, IFN-γ,TGF-β2 in the lacrimal gland. *P < 0.05 versus the normal group (N), #P < 0.05, versus the scopolamine-treated group (SCOP).</p

Lacrimal Gland Histology by H&E Staining.

<p>H&E staining of lacrimal gland from normal controls (N), the scopolamine-treated group(SCOP) and after desiccating stress in ICES for 1 week, 2week, 4 week and 6week (E1,E2,E4,E6). Arrows indicate ductal lumens. Circle indicates one acinus. Scale bars = 50μ m.</p