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OBJECTIVE: To examine the relationship between treatment-related variables for Candida bloodstream infection and hospital mortality. DESIGN: Retrospective cohort analysis. SETTING: Thousand two hundred-bed academic medical center. PATIENTS: A total of 245 consecutive patients with Candida bloodstream infections who received antifungal therapy. INTERVENTIONS: Identification of treatment-related risk factors: central vein catheter retention, inadequate initial fluconazole dosing, and delayed administration of antifungal therapy. MEASUREMENTS AND MAIN RESULTS: A total of 245 patients with Candida bloodstream infections who received antifungal therapy were identified. One hundred eleven (45.3%) patients were managed in an intensive care unit and analyzed as a separate subgroup. In the hospital cohort, 72 (29.4%) patients died during hospitalization and 40 (36.0%) patients died in the intensive care unit cohort. In the hospital cohort, logistic regression analysis identified Acute Physiology and Chronic Health Evaluation II scores (1-point increments) (adjusted odds ratio [AOR], 1.18; 95% confidence interval [CI], 1.11-1.25; p = 0.003), corticosteroid use at the time a positive blood culture was drawn (AOR, 3.41; 95% CI, 1.96-5.93; p = 0.027), inadequate initial fluconazole dosing (AOR, 3.31; 95% CI, 1.83-6.00; p = 0.044), and retention of a central vein catheter (AOR, 4.85; 95% CI, 2.54-9.29; p = 0.015) as independent determinants of hospital mortality. In the intensive care unit cohort, logistic regression analysis identified Acute Physiology and Chronic Health Evaluation II scores (1-point increments) (AOR, 1.21; 95% CI, 1.14-1.29; p = 0.001), inadequate initial fluconazole dosing (AOR, 9.22; 95% CI, 2.15-19.79; p = 0.004), and retention of a central vein catheter (AOR, 6.21; 95% CI, 3.02-12.77; p = 0.011), as independent determinants of hospital mortality. For both cohorts the incremental presence of treatment-related risk factors was statistically associated with greater hospital mortality. CONCLUSIONS: Treatment-related factors, including retention of central vein catheters and inadequate initial fluconazole dosing, were associated with increased hospital mortality in patients with Candida bloodstream infections. These data suggest that optimization of initial antifungal therapy and removal of central vein catheters may improve the outcomes of patients with Candida bloodstream infections. [ABSTRACT FROM AUTHOR]

The engineering of broadband absorbers to harvest white light in thin-film semiconductors is a major challenge in developing renewable materials for energy harvesting. Many solution-processed materials with high manufacturability and low cost, such as semiconductor quantum dots, require the use of film structures with thicknesses on the order of 1 μm to absorb incoming photons completely. The electron transport lengths in these media, however, are 1 order of magnitude smaller than this length, hampering further progress with this platform. Herein, we show that, by engineering suitably disordered nanoplasmonic structures, we have created a new class of dispersionless epsilon-near-zero composite materials that efficiently harness white light. Our nanostructures localize light in the dielectric region outside the epsilon-near-zero material with characteristic lengths of 10-100 nm, resulting in an efficient system for harvesting broadband light when a thin absorptive film is deposited on top of the structure. By using a combination of theory and experiments, we demonstrate that ultrathin layers down to 50 nm of colloidal quantum dots deposited atop the epsilon-near-zero material show an increase in broadband absorption ranging from 200% to 500% compared to a planar structure of the same colloidal quantum-dot-absorber average thickness. When the epsilon-near-zero nanostructures were used in an energy-harvesting module, we observed a spectrally averaged 170% broadband increase in the external quantum efficiency of the device, measured at wavelengths between 400 and 1200 nm. Atomic force microscopy and photoluminescence excitation measurements demonstrate that the properties of these epsilon-near-zero structures apply to general metals and could be used to enhance the near-field absorption of semiconductor structures more widely. We have developed an inexpensive electrochemical deposition process that enables scaled-up production of this nanomaterial for large-scale energy-harvesting applications.

Colloidal quantum dots (CQD) are an attractive thin-film material for photovoltaic applications due to low material costs, ease of fabrication, and size-tunable band gap. Unfortunately, today they suffer from a compromise between light absorption and photocarrier extraction, a fact that currently prevents the complete harvest of incoming above-band-gap solar photons. We have investigated the use of structured substrates and/or electrodes to increase the effective light path through the active material and found that these designs require highly conformal application of the light-absorbing films to achieve the greatest enhancement. This conformality requirement derives from the need for maximal absorption enhancement combined with shortest-distance charge transport. Here we report on a means of processing highly conformal layer-by-layer deposited CQD absorber films onto microstructured, light-recycling electrodes. Specifically, we engineer surface hydrophilicity to achieve conformal deposition of upper layers atop underlying ones. We show that only with the application of conformal coating can we achieve optimal quantum efficiency and enhanced power conversion efficiency in structured-electrode CQD cells.

Extremely thin-absorber solar cells offer low materials utilization and simplified manufacture but require improved means to enhance photon absorption in the active layer. Here, we report enhanced-absorption colloidal quantum dot (CQD) solar cells that feature transfer-stamped solution-processed pyramid-shaped electrodes employed in a hierarchically structured device. The pyramids increase, by up to a factor of 2, the external quantum efficiency of the device at absorption-limited wavelengths near the absorber band edge. We show that absorption enhancement can be optimized with increased pyramid angle with an appreciable net improvement in power conversion efficiency, that is, with the gain in current associated with improved absorption and extraction overcoming the smaller fractional decrease in open-circuit voltage associated with increased junction area. We show that the hierarchical combination of micron-scale structured electrodes with nanoscale films provides for an optimized enhancement at absorption-limited wavelengths. We fabricate 54.7° pyramid-patterned electrodes, conformally apply the quantum dot films, and report pyramid CQD solar cells that exhibit a 24% improvement in overall short-circuit current density with champion devices providing a power conversion efficiency of 9.2%.

The performance of photodetectors is judged via high responsivity, fast speed of response, and low background current. Many previously reported photodetectors based on size-tuned colloidal quantum dots (CQDs) have relied either on photodiodes, which, since they are primary photocarrier devices, lack gain; or photoconductors, which provide gain but at the expense of slow response (due to delayed charge carrier escape from sensitizing centers) and an inherent dark current vs responsivity trade-off. Here we report a photojunction field-effect transistor (photoJFET), which provides gain while breaking prior photoconductors' response/speed/dark current trade-off. This is achieved by ensuring that, in the dark, the channel is fully depleted due to a rectifying junction between a deep-work-function transparent conductive top contact (MoO3) and a moderately n-type CQD film (iodine treated PbS CQDs). We characterize the rectifying behavior of the junction and the linearity of the channel characteristics under illumination, and we observe a 10 μs rise time, a record for a gain-providing, low-dark-current CQD photodetector. We prove, using an analytical model validated using experimental measurements, that for a given response time the device provides a two-orders-of-magnitude improvement in photocurrent-to-dark-current ratio compared to photoconductors. The photoJFET, which relies on a junction gate-effect, enriches the growing family of CQD photosensitive transistors.

Solution processed colloidal quantum dot (CQD) solar cells have great potential for large area low-cost photovoltaics. However, light utilization remains low mainly due to the tradeoff between small carrier transport lengths and longer infrared photon absorption lengths. Here, we demonstrate a bottom-illuminated periodic nanostructured CQD solar cell that enhances broadband absorption without compromising charge extraction efficiency of the device. We use finite difference time domain (FDTD) simulations to study the nanostructure for implementation in a realistic device and then build proof-of-concept nanostructured solar cells, which exhibit a broadband absorption enhancement over the wavelength range of λ = 600 to 1,100 nm, leading to a 31% improvement in overall short-circuit current density compared to a planar device containing an approximately equal volume of active material. Remarkably, the improved current density is achieved using a light-absorber volume less than half that typically used in the best planar devices.

Colloidal quantum dot (CQD) solar cells combine solution-processability with quantum-size-effect tunability for low-cost harvesting of the sun's broad visible and infrared spectrum. The highest-performing colloidal quantum dot solar cells have, to date, relied on a depleted-heterojunction architecture in which an n-type transparent metal oxide such as TiO2 induces a depletion region in the p-type CQD solid. These devices have, until now, been limited by a modest depletion region depth produced in the CQD solid owing to limitations in the doping available in TiO2. Herein we report a new device geometry-one based on a donor-supply electrode (DSE)-that leads to record-performing CQD photovoltaic devices. Only by employing this new charge-extracting approach do we deepen the depletion region in the CQD solid and thereby extract notably more photocarriers, the key element in achieving record photocurrent and device performance. With the use of optoelectronic modeling corroborated by experiment, we develop the guidelines for building a superior CQD solar cell based on the DSE concept. We confirm that using a shallow-work-function terminal electrode is essential to producing improved charge extraction and enhanced performance.

Recent advances in spectrally tuned, solution-processed plasmonic nanoparticles have provided unprecedented control over light's propagation and absorption via engineering at the nanoscale. Simultaneous parallel progress in colloidal quantum dot photovoltaics offers the potential for low-cost, large-area solar power; however, these devices suffer from poor quantum efficiency in the more weakly absorbed infrared portion of the sun's spectrum. Here, we report a plasmonic-excitonic solar cell that combines two classes of solution-processed infrared materials that we tune jointly. We show through experiment and theory that a plasmonic-excitonic design using gold nanoshells with optimized single particle scattering-to-absorption cross-section ratios leads to a strong enhancement in near-field absorption and a resultant 35% enhancement in photocurrent in the performance-limiting near-infrared spectral region.

Herein, a solution-processed, bottom-up-fabricated, nanowire network electrode is developed. This electrode features a ZnO template which is converted into locally connected, infiltratable, TiO2 nanowires. This new electrode is used to build a depleted bulk heterojunction solar cell employing hybrid-passivated colloidal quantum dots. The new electrode allows the application of a thicker, and thus more light-absorbing, colloidal quantum dot active layer, from which charge extraction of an efficiency comparable to that obtained from a thinner, planar device could be obtained., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Colloidal quantum dot photovoltaics combine low-cost solution processing with quantum size-effect tuning to match absorption to the solar spectrum. Rapid advances have led to certified solar power conversion efficiencies of over 7%. Nevertheless, these devices remain held back by a compromise in the choice of quantum dot film thickness, balancing on the one hand the need to maximize photon absorption, mandating a thicker film, and, on the other, the need for efficient carrier extraction, a consideration that limits film thickness. Here we report an architecture that breaks this compromise by folding the path of light propagating in the colloidal quantum dot solid. Using this method, we achieve a substantial increase in short-circuit current, ultimately leading to improved power conversion efficiency.

Colloidal quantum dot (CQD) films allow large-area solution processing and bandgap tuning through the quantum size effect. However, the high ratio of surface area to volume makes CQD films prone to high trap state densities if surfaces are imperfectly passivated, promoting recombination of charge carriers that is detrimental to device performance. Recent advances have replaced the long insulating ligands that enable colloidal stability following synthesis with shorter organic linkers or halide anions, leading to improved passivation and higher packing densities. Although this substitution has been performed using solid-state ligand exchange, a solution-based approach is preferable because it enables increased control over the balance of charges on the surface of the quantum dot, which is essential for eliminating midgap trap states. Furthermore, the solution-based approach leverages recent progress in metal:chalcogen chemistry in the liquid phase. Here, we quantify the density of midgap trap states in CQD solids and show that the performance of CQD-based photovoltaics is now limited by electron-hole recombination due to these states. Next, using density functional theory and optoelectronic device modelling, we show that to improve this performance it is essential to bind a suitable ligand to each potential trap site on the surface of the quantum dot. We then develop a robust hybrid passivation scheme that involves introducing halide anions during the end stages of the synthesis process, which can passivate trap sites that are inaccessible to much larger organic ligands. An organic crosslinking strategy is then used to form the film. Finally, we use our hybrid passivated CQD solid to fabricate a solar cell with a certified efficiency of 7.0%, which is a record for a CQD photovoltaic device.

The size-effect tunability of colloidal quantum dots enables facile engineering of the bandgap at the time of nanoparticle synthesis. The dependence of effective bandgap on nanoparticle size also presents a challenge if the size dispersion, hence bandgap variability, is not well-controlled within a given quantum dot solid. The impact of this polydispersity is well-studied in luminescent devices as well as in unipolar electronic transport; however, the requirements on monodispersity have yet to be quantified in photovoltaics. Here we carry out a series of combined experimental and model-based studies aimed at clarifying, and quantifying, the importance of quantum dot monodispersity in photovoltaics. We successfully predict, using a simple model, the dependence of both open-circuit voltage and photoluminescence behavior on the density of small-bandgap (large-diameter) quantum dot inclusions. The model requires inclusion of trap states to explain the experimental data quantitatively. We then explore using this same experimentally tested model the implications of a broadened quantum dot population on device performance. We report that present-day colloidal quantum dot photovoltaic devices with typical inhomogeneous linewidths of 100-150 meV are dominated by surface traps, and it is for this reason that they see marginal benefit from reduction in polydispersity. Upon eliminating surface traps, achieving inhomogeneous broadening of 50 meV or less will lead to device performance that sees very little deleterious impact from polydispersity., (© 2012 American Chemical Society)

The highest-performing colloidal quantum dot (CQD) photovoltaics (PV) reported to date have relied on high-temperature (>500°C) annealing of electron-accepting TiO2. Room-temperature processing reduces energy payback time and manufacturing cost, enables flexible substrates, and permits tandem solar cells that integrate a small-bandgap back cell atop a low-thermal-budget larger-bandgap front cell. Here we report an electrode strategy that enables a depleted-heterojunction CQD PV device to be fabricated entirely at room temperature. We find that simply replacing the high-temperature-processed TiO2 with a sputtered version of the same material leads to poor performance due to the low mobility of the sputtered oxide. We develop instead a two-layer donor-supply electrode (DSE) in which a highly doped, shallow work function layer supplies a high density of free electrons to an ultrathin TiO2 layer via charge-transfer doping. Using the DSE we build all-room-temperature-processed small-bandgap (1 eV) colloidal quantum dot solar cells having 4% solar power conversion efficiency and high fill factor. These 1 eV bandgap cells are suitable for use as the back junction in tandem solar cells. The DSE concept, combined with control over TiO2 stoichiometry in sputtering, provides a much-needed tunable electrode to pair with quantum-size-effect CQD films.

Objective: Early therapy of sepsis involving fluid resuscitation and antibiotic administration has been shown to improve patient outcomes. A proactive tool to identify patients at risk for developing sepsis may decrease time to interventions and improve patient outcomes. The objective of this study was to evaluate whether the implementation of an automated sepsis screening and alert system facilitated early appropriate interventions., Design: Prospective, observational, pilot study., Setting: Six medicine wards in Barnes-Jewish Hospital, a 1250-bed academic medical center., Patients: Patients identified by the sepsis screen while admitted to a medicine ward were included in the study. A total of 300 consecutive patients were identified comprising the nonintervention group (n=200) and the intervention group (n=100)., Interventions: A real-time sepsis alert was implemented for the intervention group, which notified the charge nurse on the patient's hospital ward by text page., Measurements and Main Results: Within 12 hrs of the sepsis alert, interventions by the treating physicians were assessed, including new or escalated antibiotics, intravenous fluid administration, oxygen therapy, vasopressors, and diagnostic tests. After exclusion of patients without commitment to aggressive management, 181 patients in the nonintervention group and 89 patients in the intervention group were analyzed. Within 12 hrs of the sepsis alert, 70.8% of patients in the intervention group had received≥1 intervention vs. 55.8% in the nonintervention group (p=.018). Antibiotic escalation, intravenous fluid administration, oxygen therapy, and diagnostic tests were all increased in the intervention group. This was a single-center, institution- and patient-specific algorithm., Conclusions: The sepsis alert developed at Barnes-Jewish Hospital was shown to increase early therapeutic and diagnostic interventions among nonintensive care unit patients at risk for sepsis.

Objective: The aim of this study is to describe the initial antibiotic treatment regimens, severity of illness, and in-hospital mortality among culture-negative (CN) and culture-positive (CP) patients with health-care-associated pneumonia (HCAP)., Methods: We used a retrospective cohort study, examining adult patients with HCAP from Barnes-Jewish Hospital, a 1,200-bed urban teaching hospital., Results: Eight hundred seventy patients with HCAP were identified over a 3-year period (January 2003 through December 2005) of whom 431 (49.5%) were CP. Among the non-CP patients, 290 (66.1%) had no respiratory cultures obtained, and 149 (33.9%) had no growth or nonpathogenic oral flora identified and were classified as CN. CN patients were more likely to have received an initial antibiotic regimen (ceftriaxone +/- azithromycin or moxifloxacin) targeting community-acquired pneumonia pathogens compared with CP patients (71.8% vs 25.5%, P < .001). Severity of illness as assessed by ICU admission and mechanical ventilation (MV) was statistically lower in CN compared with CP patients (ICU admittance 12.1% vs 48.7%, P < .001; MV: 6.7% vs 44.5%, P < .001). In-hospital mortality and hospital length of stay were also statistically lower for CN patients (mortality: 7.4% vs 24.6%, P < .001; hospital length of stay: 6.7 +/- 7.4 days vs 12.1 +/- 11.7 days, P < .001)., Conclusions: In this analysis, patients with CN HCAP had lower severity of illness, hospital mortality, and hospital length of stay compared with CP patients. These data suggest that patients with CN HCAP differ substantially from patients with HCAP with positive microbiologic cultures.

Study Objectives: To evaluate the impact of inappropriate therapy--defined as delayed antifungal therapy beyond 24 hours from culture collection, inadequate antifungal dosage, or administration of an antifungal to which an isolate was considered resistant--on postculture hospital length of stay and costs, and to evaluate the relationship between modifiable risk factors, including failure to remove a central venous catheter, antifungal delay, and inadequate dosage, for an additive effect on hospital length of stay and costs., Design: Single-center retrospective cohort study., Setting: 1250-bed academic medical center., Patients: One hundred sixty-seven consecutive adult patients admitted between January 2004 and May 2006 with culture-confirmed Candida bloodstream infections that occurred within 14 days of hospital admission and who received at least one dose of antifungal treatment., Measurements and Main Results: Patients were stratified according to appropriateness of antifungal therapy. Appropriate therapy was defined as initiation of an antifungal to which the isolated pathogen was sensitive in vitro within 24 hours of positive culture collection, in addition to receipt of an adequate dose as recommended by the Infectious Diseases Society of America and the antifungal package insert. Postculture length of stay was the primary outcome and hospital costs the secondary outcome. An evaluation of modifiable risk factors was performed separately. Data were analyzed for 167 patients (22 in the appropriate therapy group and 145 in the inappropriate therapy group). Postculture length of stay was shorter in the appropriate therapy group (mean 7 vs 10.4 days, p=0.037). This correlated with total hospital costs that were lower in the appropriate therapy group (mean $15,832 vs $33,021, p<0.001.) A graded increase in costs was noted with increasing number of modifiable risk factors (p=0.001)., Conclusion: Inappropriate therapy for Candida bloodstream infection occurring within 14 days of hospitalization was associated with prolonged postculture length of stay and increased costs. A rise in costs, but not length of stay, was noted with increasing modifiable risk factors.