Sub-Bandgap Sensitization of Perovskite Semiconductors via Colloidal Quantum Dots Incorporation.

By taking advantage of the outstanding intrinsic optoelectronic properties of perovskite-based photovoltaic materials, together with the strong near-infrared (NIR) absorption and electronic confinement in PbS quantum dots (QDs), sub-bandgap photocurrent generation is possible, opening the way for solar cell efficiencies surpassing the classical limits. The present study shows an effective methodology for the inclusion of high densities of colloidal PbS QDs in a MAPbI3 (methylammonium lead iodide) perovskite matrix as a means to enhance the spectral window of photon absorption of the perovskite host film and allow photocurrent production below its bandgap. The QDs were introduced in the perovskite matrix in different sizes and concentrations to study the formation of quantum-confined levels within the host bandgap and the potential formation of a delocalized intermediate mini-band (IB). Pronounced sub-bandgap (in NIR) absorption was optically confirmed with the introduction of QDs in the perovskite. The consequent photocurrent generation was demonstrated via photoconductivity measurements, which indicated IB establishment in the films. Despite verifying the reduced crystallinity of the MAPbI3 matrix with a higher concentration and size of the embedded QDs, the nanostructured films showed pronounced enhancement (above 10-fold) in NIR absorption and consequent photocurrent generation at photon energies below the perovskite bandgap.

Light management with quantum nanostructured dots-in-host semiconductors.

Insightful knowledge on quantum nanostructured materials is paramount to engineer and exploit their vast gamut of applications. Here, a formalism based on the single-band effective mass equation was developed to determine the light absorption of colloidal quantum dots (CQDs) embedded in a wider bandgap semiconductor host, employing only three parameters (dots/host potential barrier, effective mass, and QD size). It was ascertained how to tune such parameters to design the energy level structure and consequent optical response. Our findings show that the CQD size has the biggest effect on the number and energy of the confined levels, while the potential barrier causes a linear shift of their values. While smaller QDs allow wider energetic separation between levels (as desired for most quantum-based technologies), the larger dots with higher number of levels are those that exhibit the strongest absorption. Nevertheless, it was unprecedently shown that such quantum-enabled absorption coefficients can reach the levels (104-105 cm-1) of bulk semiconductors.

One-step affinity purification of urease from jack beans.

Jack bean (Canivalia ensiformis) urease (EC3.5.1.5) was purified in one-step by ligand affinity chromatography using epoxy-activated Sepharose 6B-urea. The yield of the purified enzyme was about 80% with a specific activity of about 500 U/mg of protein. The enzyme was apparently homogeneous when analyzed by SDS-PAGE and native PAGE. The protein band on native PAGE coincided with the stained band of urease activity. The affinity column could be regenerated and reused several times without any loss of binding capacity and resolution. Affinity gels containing either acetamide or semicarbazide as affinity ligands were also found to be useful for the isolation of urease.

Human insulin allergy-immediate and late type III reactions in a long-standing IDDM patient.

UNLABELLED: Human insulin allergy-immediate or late type III reaction-is a rare event. We report the case of a 33-year-old female patient with insulin-dependent diabetes mellitus for 25 years who presented, in the last 8 years, mild but generalized urticaria partially controlled with oral antihistamines. There was no improvement after changing from mixed beef-pork to human insulin. In the last 3 years another allergic manifestation began: small, localized, subdermal and painful non-erythematous nodules with central hematomas at injection sites, occurring 6-8 h after the insulin injection and lasting for 48 h. The following maneuvers had no benefit: (1) Human insulin (NPH or Lente) administered with dexametasone or xylocain locally, (2) Short acting human insulin with or without previous boiling, (3) Anti-histamine cetirizine dihydrochloride-10 mg/day. The allergic symptoms disappeared only after treatment with short acting human insulin (up to 100 U/day) associated to prednisone-40 mg/day and cetirizine dihydrochloride for 4 months. However, after stopping prednisone the urticaria reappeared and it was relieved with insulin desensitization. The pain at the site of injections persisted. CONCLUSION: This long-standing IDDM patient presented two types of reactions to human insulin: the immediate type (systemic urticaria), treated with antihistamines and desensitization, and the Arthus' type III reaction (nodules and hematomas occurring 6-8 h after the insulin injection) that required glucocorticoid therapy for more than 4 months.

[Foreign-body aspiration in adults]. / Aspiração de corpo estranho em adulto.

Proximal airway obstruction and acute life-threatening asphyxia is the most important complication of foreign body aspiration. Small foreign bodies that transverse the larynx may be initially asymptomatic appearing serious respiratory disturbances only later. Three patients with different clinical evolutions are reported and the diagnostic and therapeutic approaches, discussed.

Aspiracao de corpo estranho em adulto / Foreign-body aspiration in adult

A obstrucao de via aerea proximal levando a asfixia com risco de vida imediato e o evento mais importante na aspiracao de corpo estranho. Contudo, pequenos corpos estranhos que atravessam a laringe sao geralmente assintomaticos no inicio e provocam sintomas respiratorios semanas ou anos antes do diagnostico. Nos descrevemos tres pacientes com evolucao clinica diferente e revisamos tecnicas de diagnostico e abordagens terapeuticas.