Enhancing the photocatalytic properties of PbS QD solids: the ligand exchange approach

Surface engineering of nanomaterials is a promising tool towards the design of new materials for conversion of solar energy into chemical energy. In this work, we examine the influence of ligand exchange on the photocatalytic performance of solution-processed PbS films. We test different ligands such as oleylamine (OAm), 1,2-ethanedithiol (EDT), 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The study demonstrates that PbS films capped with MPA and EDT exhibit 3.5-fold enhanced photocatalytic performance for the photodecomposition of methyl orange upon sunlight exposure. Both band energy alignment and charge carrier transport have a strong impact on the generation of reactive oxygen species (ROS), which play a key role in the photodecomposition process. Moreover, the stability and reusability of the photocatalysts are clearly improved after ligand exchange. We prove how both MPA and EDT provide much more stability to PbS QD films to operate very efficiently up to 8 cycles of photocatalysis. As observed in XPS, the oxidation of PbS is prevented after ligand exchange. We demonstrate how surface chemistry engineering of solution-processed QD films can open a new approach towards the design of highly efficient and stable visible-light-driven photocatalysts, which paves the way to low cost and large area fabrication of high-performance photocatalytic devices.

Strongly-coupled PbS QD solids by doctor blading for IR photodetection

In this work, doctor blading is proposed for the fabrication of strongly-coupled QD solids from a PbS nanoink for photodetection at telecom wavelengths.

Suspected pulmonary tuberculosis in rural South Africa--sputum induction as a simple diagnostic tool?

OBJECTIVES

To assess the value of sputum induction (SI) as a diagnostic tool for patients with suspected pulmonary tuberculosis (PTB) who are unable to expectorate or who have a negative sputum smear.

DESIGN

Study of an inpatient cohort undergoing SI.

SETTING

Mseleni Hospital, a rural district hospital in northern KwaZulu-Natal.

SUBJECTS

All adult patients with suspected TB seen at the hospital over a 4-month period.

OUTCOME MEASURES

(i) Successful SI; (ii) sputum acid-fast smear result; (iii) change of admission diagnosis as a result of the induction procedure; and (iv) number of patients discharged with a diagnosis other than TB who represented within 4 months with TB.

RESULTS

A total of 51 patients (31 female) underwent SI; of these 36 (71%) were able to produce a sputum sample. Fifteen (42%) of those were acid-fast smear-positive (29% of all patients included). The admission diagnosis was changed in 16 (44%) of the patients who were able to give an induced sputum sample as opposed to 4 (27%) who had been unable to expectorate despite an induction attempt (P = 0.38). Three (12.5%) of the 24 patients with a discharge diagnosis other than TB (17 pneumonia, 3 old TB, 2 carcinoma of the lung, 1 bronchiectasis) turned out to have TB within the follow-up period; 2 of those had extrapulmonary TB.

CONCLUSION

SI produced a positive smear result in 29% of patients with suspected TB who had previously been smear-negative or unable to expectorate. The method proved an aid to clinical decision making.