Correction: Robrigado et al. Bridge Healing: A Pilot Project of a New Model to Prevent Repeat "Social Admit" Visits to the Emergency Department and Help Break the Cycle of Homelessness in Canada. Int. J. Environ. Res. Public Health 2023, 20, 6845.

There was an error in the original publication [...].

Bridge Healing: A Pilot Project of a New Model to Prevent Repeat "Social Admit" Visits to the Emergency Department and Help Break the Cycle of Homelessness in Canada.

Homelessness continues to be a pervasive public health problem throughout Canada. Hospital Emergency Departments (EDs) and inpatient wards have become a source of temporary care and shelter for homeless patients. Upon leaving the hospital, homeless patients are not more equipped than before to find permanent housing. The Bridge Healing program in Edmonton, Alberta, has emerged as a novel approach to addressing homelessness by providing transitional housing for those relying on repeated visits to the ED. This paper describes the three essential components to the Bridge Healing model: partnership between the ED and a Housing First community organization; facility design based on The Eden Alternative™ principles; and grassroots community funding. This paper, in conjunction with the current pilot project of the Bridge Healing facilities, serves as a proof of concept for the model and can inform transitional housing approaches in other communities.

Public health measures to reduce the risk of SARS-CoV-2 transmission in Canada during the early days of the COVID-19 pandemic: a scoping review.

OBJECTIVE: The main objectives of this study were to synthesise and compare pandemic preparedness strategies issued by the federal and provincial/territorial (P/T) governments in Canada and to assess whether COVID-19 public health (PH) measures were tailored towards priority populations, as defined by relevant social determinants of health. METHODS: This scoping review searched federal and P/T websites on daily COVID-19 pandemic preparedness strategies between 30 January and 30 April 2020. The PROGRESS-Plus equity-lens framework was used to define priority populations. All definitions, policies and guidelines of PH strategies implemented by the federal and P/T governments to reduce risk of SARS-CoV-2 transmission were included. PH measures were classified using a modified Public Health Agency of Canada Framework for Canadian Pandemic Influenza Preparedness. RESULTS: A total of 722 COVID-19 PH measures were issued during the study period. Of these, home quarantine (voluntary) (n=13.0%; 94/722) and retail/commerce restrictions (10.9%; n=79/722) were the most common measures introduced. Many of the PH orders, including physical distancing, cancellation of mass gatherings, school closures or retail/commerce restrictions began to be introduced after 11 March 2020. Lifting of some of the PH orders in phases to reopen the economy began in April 2020 (6.5%; n=47/722). The majority (68%, n=491/722) of COVID-19 PH announcements were deemed mandatory, while 32% (n=231/722) were recommendations. Several PH measures (28.0%, n=202/722) targeted a variety of groups at risk of socially produced health inequalities, such as age, religion, occupation and migration status. CONCLUSIONS: Most PH measures centred on limiting contact between people who were not from the same household. PH measures were evolutionary in nature, reflecting new evidence that emerged throughout the pandemic. Although ~30% of all implemented COVID-19 PH measures were tailored towards priority groups, there were still unintended consequences on these populations.

Faradaic efficiency of O2 evolution on metal nanoparticle sensitized hematite photoanodes.

Functionalization of transition metal oxides using metallic nanoparticles is an interesting route towards efficient photoelectrochemical hydrogen production via water splitting. Although an enhanced photocurrent in photoanodes upon functionalization with metallic nanostructures has been observed in several studies, to the best of our knowledge no measurements of the Faradaic efficiency (FE) of the oxygen evolution reaction (OER) have been reported for such systems. This work characterizes the FE on a model system consisting of ultra-thin films of hematite (Fe2O3) sensitized with Ti/Au nanodisks. Compared to bare hematite references, sensitized samples showed significantly enhanced photocurrents as well as O2 evolution. Experimental evidence suggests that the observed enhancement was not due to photocatalytic activity of the nanodisks. The FE has been determined to be 100%, within the experimental errors, for both sensitized and reference samples. Also, this work demonstrates that the sensitized samples were stable for at least 16 hours photocurrent testing. The concepts shown in this work are generally applicable to any situation in which a semiconductor has its water splitting performance enhanced by metallic nanostructures.

Combined in situ quartz crystal microbalance with dissipation monitoring, indirect nanoplasmonic sensing, and vibrational sum frequency spectroscopic monitoring of alkanethiol-protected copper corrosion.

In this study, we have applied three techniques to simultaneously and in situ study the initial stage of corrosion of copper protected by a self-assembled monolayer of octadecanethiol (ODT). We combined quartz crystal microbalance with dissipation monitoring (QCM-D), indirect nanoplasmonic sensing (INPS), and vibrational sum frequency spectroscopy (VSFS) and obtained complementary information about mass uptake and optical and spectroscopic changes taking place during the initial corrosion phase. All three techniques are very sensitive to the formation of a corrosion film (thickness in the range 0-0.41 nm) under mildly corrosive conditions (dry air, <0.5% relative humidity). The three techniques yield information about the viscoelasticity of the corrosion film (QCM-D), the homogeneity of the corrosion reaction on the surface (INPS), and the stability of the ODT protection layer (VSFS). Furthermore, by also studying the corrosion process in humid air (ca. 70% relative humidity), we illustrate how the combination of these techniques can be used to differentiate between simultaneously occurring processes, such as water adsorption and corrosion product formation.

Localized and propagating plasmons in metal films with nanoholes.

The occurrence of plasmon resonances in thin (~20 nm) Al and Au films, perforated with nanoholes, was studied. In both metals, two plasmon resonances were observed: (i) A surface plasmon polariton mode associated with a maximum in extinction and (ii) a localized resonance in the nanohole associated with a minimum in extinction. By varying the diameter of the nanoholes, the scaling of the peak positions of the plasmon resonances was determined as a function of hole diameter. In the large nanohole limit, the plasmon peak positions depend only on the nanohole diameter being independent of the material. On the other hand, for small nanoholes the plasmon peak positions are material and size dependent. In contrast to Al films where the localized plasmons can be excited from the near-IR to the UV, no plasmon resonances were observed for Au at energies above the interband threshold (2.4 eV). The interaction between a distinct interband transition in Al at 1.5 eV and the localized plasmon resonance is considered in detail. We observe for the first time experimentally a noncrossing behavior of the interband transition and the localized plasmon resonance. The energy (size) dependence of surface plasmon peak width, being a measure for the decay/damping of the latter, is very different for the two metals. This can be explained by considering the different decay mechanisms active in the two metals. Apart from these basic plasmonics results, we test the potential of using the shifts of the plasmon resonances in perforated Al films to follow the atmospheric oxidation/corrosion kinetics of Al. The results are quantified by model calculations. The obtained kinetic law for the oxide growth is in good agreement with a previous XPS study on plain Al films. This suggests that the nanohole-induced plasmon resonances can be a sensitive and simple measure for Al corrosion and metal corrosion in general.

On the mechanism for nanoplasmonic enhancement of photon to electron conversion in nanoparticle sensitized hematite films.

Hematite (Fe2O3) is a promising candidate for hydrogen production via water splitting despite the difference in the characteristic lengths for photon absorption and charge carrier transport. Metallic nanoparticles supporting localized surface plasmon resonances (LSPRs), i.e. collective, non-propagating oscillations of electrons excited by an external electric field, are well-suited to improve the optoelectronic properties of hematite, in particular for ultra-thin films. Several mechanisms have been proposed to explain the observed LSPR mediated performance enhancement. In this work, the improvement of incident photon-to-electron conversion efficiency (IPCE) of ultra-thin hematite photoanodes functionalized with Au nanodisks was investigated. The improvement in IPCE at wavelengths close to the bandgap in hematite was found to correlate well with the increase in optical extinction owing to the excitation of LSPR in the nanodisks. Finite-difference time-domain calculations of the near-field distribution around the nanodisks enabled us to elucidate the mechanism behind the IPCE enhancement and its variations with the position of the plasmonic resonance with respect to the bandgap of hematite. Both were attributed to an increased charge generation close to the hematite-electrolyte interface caused by the electric field enhancement in hematite. The results presented here are directly applicable to other semiconductors with similar properties to hematite and are expected to be helpful in future design of optimized photoanodes, where, for instance, functionalization with metallic nanoparticles is combined with material doping and nanostructuring.

Diffraction from arrays of plasmonic nanoparticles with short-range lateral order.

We have measured the angular distribution of light scattered off 2D plasmonic Al nanoparticle ensembles. We created these samples with disk-like nanoparticles, 175 and 500 nm in diameter, respectively, using hole-mask colloidal lithography and electron beam lithography. The nanoparticle arrangements in the samples display the short-range order (but no long-range order) characteristic for an ensemble formed by random sequential adsorption. As a consequence of this, the ensemble scattering patterns can be quantitatively well described by combining the single-particle scattering pattern with a static structure factor that carries information about the diffraction effects caused by the short-range order of the ensemble. We also performed sensing experiments in which we monitored changes in the angle-resolved scattering intensity for a fixed wavelength as a function of the thickness of an ultrathin SiO(2) coating covering the Al nanoparticles. The data show that the angle and strength of the main diffraction peak vary linearly with SiO(2) coating thickness in the range 1.5-4.5 nm and suggest that measurements of the scattering profile could be a competitive alternative to traditional transmission measurements in terms of sensitivity.

Oscillatory optical response of an amorphous two-dimensional array of gold nanoparticles.

The optical response of metallic nanoparticle arrays is dominated by localized surface plasmon excitations and is the sum of individual particle contributions modified by interparticle coupling that depends on specific array geometry. We demonstrate a so far unexplored distinct oscillatory behavior of the plasmon peak position, full width at half maximum, and extinction efficiency in large area amorphous arrays of Au nanodisks, which depend on the minimum particle center-to-center distance in the array. Amorphous arrays exhibit short-range order and are completely random at long distances. In our theoretical analysis we introduce a film of dipoles approach, within the framework of the coupled dipole approximation, which describes the array as an average particle surrounded by a continuum of dipoles with surface densities determined by the pair correlation function of the array.

Gold, platinum, and aluminum nanodisk plasmons: material independence, subradiance, and damping mechanisms.

Localized surface plasmon resonances (LSPR) are collective electronic excitations in metallic nanoparticles. The LSPR spectral peak position, as a function of nanoparticle size and material, is known to depend primarily on dynamic depolarization and electron structure related effects. The former gives rise to the well-known spectral red shift with increasing nanoparticle size. A corresponding understanding of the LSPR spectral line width for a wide range of nanoparticle sizes and different metals does, however, not exist. In this work, the radiative and nonradiative damping contributions to the LSPR line width over a broad nanoparticle size range (40-500 nm) for a selection of three metals with fundamentally different bulk dielectric properties (Au, Pt, and Al) are explored experimentally and theoretically. Excellent agreement was obtained between the observed experimental trends and the predictions based on electrostatic spheroid theory (MLWA), and the obtained results were successfully related to the specific band structure of the respective metal. Moreover, for the first time, a clear transition from a radiation damping dominated to a quenched radiation damping regime (subradiance) in large nanoparticles was observed and probed by varying the electron density through appropriate material choice. To minimize inhomogeneous broadening (commonly present in ensemble-based spectroscopic measurements), a novel, electron-beam lithography (EBL)-based nanofabrication method was developed. The method generates large-area 2D patterns of randomly distributed nanodisks with well-defined size and shape, narrow size distribution, and tunable (minimum) interparticle distance. In order to minimize particle-particle coupling effects, sparse patterns with a large interparticle distance (center-to-center ≥6 particle diameters) were considered.

Indirect nanoplasmonic sensing: ultrasensitive experimental platform for nanomaterials science and optical nanocalorimetry.

Indirect nanoplasmonic sensing is a novel experimental platform for measurements of thermodynamics and kinetics in/on nanomaterials and thin films. It features simple experimental setup, high sensitivity, small sample amounts, high temporal resolution (<10(-3) s), operating conditions from UHV to high pressure, wide temperature range, and applicability to any nano- or thin film material. The method utilizes two-dimensional arrangements of nanoplasmonic Au sensor-nanoparticles coated with a thin dielectric spacer layer onto which the sample material is deposited. The measured signal is spectral shifts of the Au-sensor localized plasmons, induced by processes in/on the sample material. Here, the method is applied to three systems exhibiting nanosize effects, (i) the glass transition of confined polymers, (ii) catalytic light-off on Pd nanocatalysts, and (iii) thermodynamics and kinetics of hydrogen uptake/release in Pd nanoparticles <5 nm. In (i) and (iii), dielectric changes in the sample are detected, while (ii) demonstrates a novel optical nanocalorimetry method.

Size-dependent kinetics of hydriding and dehydriding of Pd nanoparticles.

Using a new indirect nanoplasmonic sensing method with subsecond resolution, we have studied hydriding and dehydriding kinetics of Pd nanoparticles in the size range 1.8-5.4 nm. Strong particle-size effects are observed. The scaling of the hydriding and dehydriding time scales satisfies power and power-exponential laws. The former (with an exponent of 2.9) is in perfect agreement with Monte Carlo simulations of diffusion-controlled hydriding kinetics. The latter is explained by the effect of surface tension on hydrogen desorption from the surface layer. The approach is generalizable to other reactant-nanoparticle systems.

LSPR study of the kinetics of the liquid-solid phase transition in Sn nanoparticles.

Using the localized surface plasmon resonance as a probe in solid and liquid Sn nanoparticles of 107 nm diameter and 52 nm height, we have studied their kinetics of melting and freezing at temperature ramps and, for the first time, at fixed temperatures. During temperature ramps, the kinetics exhibit distinct hysteresis. The melting occurs near the bulk melting point while the freezing is observed at much lower temperatures so that the undercooling interval is approximately 130 K. The time scale of the freezing kinetics measured at different fixed temperatures rapidly decreases as the latter are lowered. All these findings have been quantitatively described by assuming the nucleation to occur on the edges of nanoparticles and employing the classical nucleation theory with the corresponding modifications.

Nanoplasmonic probes of catalytic reactions.

Optical probes of heterogeneous catalytic reactions can be valuable tools for optimization and process control because they can operate under realistic conditions, but often probes lack sensitivity. We have developed a plasmonic sensing method for such reactions based on arrays of nanofabricated gold disks, covered by a thin (approximately 10 nanometer) coating (catalyst support) on which the catalyst nanoparticles are deposited. The sensing particles monitor changes in surface coverage of reactants during catalytic reaction through peak shifts in the optical extinction spectrum. Sensitivities to below 10(-3) monolayers are estimated. The capacity of the method is demonstrated for three catalytic reactions, CO and H2 oxidation on Pt, and NO(x) conversion to N2 on Pt/BaO.

A nanocell for quartz crystal microbalance and quartz crystal microbalance with dissipation-monitoring sensing.

A novel device for nanometer-confinement of soft matter in one dimension (1D) is presented. This nanocell, with very large (up to 10(6):1) cell-radius to cell-height ratio, is tailored as an accessory for quartz crystal microbalance (QCM) and QCM with dissipation-monitoring (QCM-D) sensing to study internal and interfacial energy dissipation phenomena in highly confined (in 1D) soft matter and fluid films (patent pending). The cell consists of two macroscopic plates (diameter of 9 mm), a top (the "lid") and a bottom (the QCM-D sensor), separated by appropriate spacers with heights ranging from below 100 nm up to 10 microm. The surfaces of both the lid and the bottom plate can be mechanically or/and chemically modified, prior to cell assembly, in order to tailor desired interfacial properties for the experiment. The cell is mounted on a standard QCM-D sensor, an AT-cut quartz crystal (the quartz crystal is cut at an angle of 35 degrees from its ZX-plane), forming the bottom plate. We illustrate theoretically and experimentally, as application examples, the use of this device for studies of dynamic mass loading and internal energy dissipation processes in thin films of ethylene glycol respective thin liquid crystal films around the nematic-isotropic phase transition.

Intrinsic Fano interference of localized plasmons in Pd nanoparticles.

Palladium (Pd) nanoparticles exhibit broad optical resonances that have been assigned to so-called localized surface plasmons (LSPs). The resonance's energy varies with particle shape in a similar fashion as is well known for LSPs in gold and silver nanoparticles, but the line-shape is always anomalously asymmetric. We here show that this effect is due to an intrinsic Fano interference caused by the coupling between the plasmon response and a structureless background originating from interband transitions. The conclusions are supported by experimental and numerical simulation data of Pd particles of different shape and phenomenologically analyzed in terms of the point dipole polarizability of spheroids. The latter analysis indicates that the degree of Fano asymmetry is simply linearly proportional to the imaginary part of the interband contribution to the metal dielectric function.

A combined nanoplasmonic and electrodeless quartz crystal microbalance setup.

We have developed an instrument combining localized surface plasmon resonance (LSPR) sensing with electrodeless quartz crystal microbalance with dissipation monitoring (QCM-D). The two techniques can be run simultaneously, on the same sensor surface, and with the same time resolution and sensitivity as for the individual techniques. The electrodeless QCM eliminates the need to fabricate electrodes on the quartz crystal and gives a large flexibility in choosing the surface structure and coating for both QCM-D and LSPR. The performance is demonstrated for liquid phase measurements of lipid bilayer formation and biorecognition events, and for gas phase measurements of hydrogen uptake/release by palladium nanoparticles. Advantages of using the combined equipment for biomolecular adsorption studies include synchronized information about structural transformations and extraction of molecular (dry) mass and degree of hydration of the adlayer, which cannot be obtained with the individual techniques. In hydrogen storage studies the combined equipment, allows for synchronized measurements of uptake/release kinetics and quantification of stored hydrogen amounts in nanoparticles and films at practically interesting hydrogen pressures and temperatures.

Localized surface plasmon resonances in aluminum nanodisks.

The plasmonic properties of arrays of supported Al nanodisks, fabricated by hole-mask colloidal lithography (HCL), are analyzed for the disk diameter range 61-492 nm at a constant disk height of 20 nm. Strong and well-defined (UV-vis-NIR) localized surface plasmon resonances are found and experimentally characterized with respect to spectral peak positions, peak widths, total cross sections, and radiative and nonradiative decay channels. Theoretically, the plasmon excitations are described by electrostatic spheroid theory. Very good qualitative and quantitative agreement between model and experiment is found for all these observables by assuming a nanoparticle embedded in a few nanometer thick homogeneous (native) aluminum oxide shell. Other addressed aspects are: (i) the role of the strong interband transition in Al metal, located at 1.5 eV, for the plasmonic excitations of Al nanoparticles, (ii) the role of the native oxide layer, and (iii) the possibility of using the plasmon excitation as an ultrasensitive, remote, real-time probe for studies of oxidation/corrosion kinetics in metal nanoparticle systems.