Size-Regulated Hole and Triplet Energy Transfer from CdSe Quantum Dots to Organic Acceptors for Enhancing Singlet Oxygen Generation.

Triplet energy transfer (TET) from semiconductor quantum dots (QDs) is an emerging strategy for sensitizing molecular triplets that have great potential in many applications. Here, CdSe QDs with varying sizes and 1-pyrenecarboxylic acid (PCA) are selected as the triplet donor and acceptor, respectively, to study the TET and charge transfer dynamics as well as enhanced singlet oxygen (1O2) generation properties. The results from static and transient spectroscopy measurements demonstrate that both the TET and hole transfer occur at the QDs-PCA interface. The observed significant drop in TET efficiency from 52 to 8% with increasing QD size results from the reduced TET driving force between the QDs and PCA, which is further confirmed by the more efficient sensitization of the anthracene derivative with a large TET driving force. In contrast, the hole transfer efficiency displays a small decrease with an increasing QD size due to a slight change in the hole driving force. The sensitized PCA triplets show a good ability of 1O2 generation, and the 1O2 formation rate increases 10-fold as the QD size decreases from 3.3 to 2.4 nm. These findings provide a profound understanding of the TET and hole transfer mechanism from QDs to molecules and are significant in designing efficient 1O2 generation systems based on semiconductor QDs and triplet molecules.

Triplet generation at the CdTe quantum dot/anthracene interface mediated by hot and thermalized electron exchange for enhanced production of singlet oxygen.

Triplet energy transfer (TET) from semiconductor quantum dots (QDs) to molecular triplets has potential applications in photon up-conversion and singlet oxygen generation. Here, we have constructed a complex consisting of CdTe QDs as the donor and 9-anthracenecarboxylic acid (ACA) as the triplet acceptor, and studied the TET pathways and enhanced singlet oxygen generation properties. The results from steady-state and time-resolved spectroscopy demonstrate efficient TET with a total efficiency of over 80% from photoexcited CdTe QDs to ACA. Dynamical analysis clearly indicates two distinctive TET channels - hot electron exchange and thermalized electron exchange - mediating the TET process in the CdTe QDs-ACA complex. The TET efficiencies from hot electron exchange at high energetic levels and thermalized electron exchange on the lowest exciton state can reach ∼27% and ∼85%, respectively, following 530 nm excitation. This efficient TET endows the CdTe QDs-ACA complex with a good capability of generating singlet oxygen species with a yield of up to ∼59%. These findings contribute further insights to the mechanisms of interfacial TET processes and are significant in designing efficient TET systems based on semiconductor nanoparticles and triplet molecules.

Differences in the evolution of surface-microstructured silicon fabricated by femtosecond laser pulses with different wavelength.

We experimentally investigate the differences in the evolution of surface-microstructured silicon fabricated by femtosecond laser pulses with different wavelength as a function of irradiated laser energy. The results show that when laser energy absorbed by the silicon material is the same, laser pulses with a shorter wavelength can form the surface-microstructured silicon with less laser energy, while the corresponding spike height is much lower than that of laser pulses with a longer wavelength. This is because the penetration depth of the laser pulses increases exponentially at the increase of the laser wavelength. Additionally, for two laser pulses with the certain wavelength and the certain absorption efficiency of silicon, the proportional relations between their formed spike height and irradiated laser energy should be determined. In particular, the average spike height is 3 times with 8 times corresponding energy for 800 nm laser pulses than that of 400 nm. These results are a benefit for the fast and optimum-morphology preparation of microstructured silicon.

Optimal proportional relation between laser power and pulse number for the fabrication of surface-microstructured silicon.

We experimentally demonstrate that, under the same laser fluence, there exists an optimal proportional relation between the laser power and pulse number for the fabrication of surface-microstructured silicon. During this fabrication process, the pulse number represents the interaction time between the laser and the silicon, which determines the depth of energy transferred into the inner part of the material, while the laser power determines the ablation and volatilization rate of the silicon. The proper combination of laser power and pulse number can ablate the material on the silicon surface effectively and have enough time to transfer the energy into the deep layer, which can produce microstructured silicon with a high spike. In addition, we compare the absorptance of samples etched by different combinations of laser power and pulse number; the corresponding results further prove the existence of an optimal proportional relation.

Prognostic significance of serum translocator protein in patients with traumatic brain injury.

BACKGROUND: Translocator protein (TP) is related to inflammation and is involved in brain injury. The objective of this study was to ascertain whether serum TP concentrations are associated with the severity and prognosis of traumatic brain injury (TBI). METHODS: We quantified the serum concentrations of TP in 106 healthy controls and 106 patients with severe TBI. Recorded prognostic variables included acute lung injury, acute traumatic coagulopathy, progressive hemorrhagic injury, posttraumatic cerebral infarction, 6-month mortality and 6-month poor outcome (Glasgow Outcome Scale score of 1-3). Trauma severity was assessed by Glasgow coma scale (GCS) score. Extent of inflammatory response was indicated by serum interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-a) and C-reactive protein (CRP) concentrations. RESULTS: Patients had significantly higher serum TP concentrations than controls. Among patients, serum TP concentrations strongly and independently correlated with GCS score and serum IL-6, TNF-a and CRP concentrations. Serum TP was identified as an independent predictor for the preceding prognostic variables, its prognostic predictive ability was similar to that of GCS score and it also significantly improved prognostic predictive ability of GCS score. CONCLUSION: Serum TP may be intimately linked with in inflammation, disease progression and poor prognosis in TBI patients.

Plasma visfatin, associated with a genetic polymorphism -1535C>T, is correlated with C-reactive protein in Chinese Han patients with traumatic brain injury.

Visfatin is a newly identified pro-inflammatory adipokine and a genetic polymorphism -1535 C>T located in the visfatin gene promoter has been suggested to be associated with the regulation of visfatin expression in some inflammatory illness. However, there were some conflicting results regarding whether this variant is functional or not. This study aimed to examine the relations of the -1535 C>T single nucleotide polymorphism (SNP) of visfatin gene to the plasma visfatin and C-reactive protein concentrations in traumatic brain injury (TBI). 318 Chinese Han patients with TBI were recruited in this study. Plasma visfatin and C-reactive protein levels were significantly different between the genotypes in the SNP-1535 C>T even after adjustment for age, sex and body mass index. The genotype C-C had the highest plasma visfatin and C-reactive protein concentrations. The plasma visfatin and C-reactive protein concentrations between the variant genotypes C-T and T-T did not differ significantly. Plasma visfatin level was significantly associated with plasma C-reactive protein level using multivariate linear regression. Thus, the SNP-1535 C>T of visfatin gene seemed to be potentially involved in the inflammatory component of TBI through a decreased production of visfatin.

Change in plasma visfatin level after severe traumatic brain injury.

Higher plasma visfatin concentration has been associated with ischemic stroke. Thus, we sought to investigate change in plasma visfatin level after traumatic brain injury and to evaluate its relation with disease outcome. Seventy-six healthy controls and 98 patients with acute severe traumatic brain injury were recruited. Twenty-seven patients (27.6%) died and 48 patients (49.0%) suffered from unfavorable outcome (Glasgow outcome scale score of 1-3) in 6 months. On admission, plasma visfatin level was increased in patients than in healthy controls and was highly correlated with Glasgow Coma Scale score. A multivariate analysis identified plasma visfatin level as an independent predictor for 6-month mortality and unfavorable outcome. According to receiver operating characteristic curve analysis, the predictive value of the plasma visfatin concentration was similar to Glasgow Coma Scale score's. In a combined logistic-regression model, visfatin did not improve the predictive value of Glasgow Coma Scale score. Thus, increased plasma visfatin level is associated with 6-month clinical outcomes after severe traumatic brain injury.