Comparing the Cubic and Tetragonal Phases of MAPbI3 at Room Temperature.

Stability and maintenance of the crystal structure are the main drawbacks of the application of organic-inorganic perovskites in photovoltaic devices. The ΔT = 62 K robust shift of the structural phase transition observed here allows us to conduct a comprehensive study at room temperature of the tetragonal versus cubic phase on MAPbI3. The absence of the shift in the cubic transition for all-inorganic CsPbI3 samples confirms the importance of both orientation and dynamics of the organic cations. Our results provide a unique opportunity to evaluate the physical properties of both cubic and tetragonal phases of MAPbI3 at the same temperature, eliminating different phonon effects as possible causes for different properties. Besides higher electrical resistivity, the perovskite cubic phase presents a faster charge carrier lifetime than the tetragonal phase and partial PL quenching, pointing toward increased trap-assisted nonradiative recombination. The light absorption coefficient in the cubic phase is larger than the absorption in the tetragonal phase in the green region.

How cation nature controls the bandgap and bulk Rashba splitting of halide perovskites.

Because of instability issues presented by metal halide perovskites based on methylammonium (MA), its replacement to Cs has emerged as an alternative to improve the materials' durability. However, the impact of this replacement on electronic properties, especially gap energy and bulk Rashba splitting remains unclear since electrostatic interactions from organic cations can play a crucial role. Through first-principles calculations, we investigated how organic/inorganic cations impact the electronic properties of MAPbI 3 and CsPbI 3 perovskites. Although at high temperatures the organic cation can assume spherical-like configurations due to its rotation into the cages, our results provide a complete electronic mechanism to show, from a chemical perspective based on ab initio calculations at 0 K , how the MA dipoles suppression can reduce the MAPbI 3 gap energy by promoting a degeneracy breaking in the electronic states from the PbI 3 framework, while the dipole moment reinforcement is crucial to align theory ↔ experiment, increasing the bulk Rashba splitting through higher Pb off-centering motifs. The lack of permanent dipole moment in Cs results in CsPbI 3 polymorphs with a pronounced Pb on-centering-like feature, which causes suppression in their respective bulk Rashba effect.

"Non-metastatic, Castration-resistant Prostate Cancer: Diagnostic and Treatment Recommendations by an Expert Panel from Brazil".

INTRODUCTION: Non-metastatic, castration-resistant prostate cancer (nmCRPC) is an important clinical stage of prostate cancer, prior to morbidity and mortality from clinical metastases. In particular, the introduction of novel androgen-receptor signaling inhibitors (ARSi) has changed the therapeutic landscape in nmCRPC. Given recent developments in this field, we update our recommendations for the management of nmCRPC. METHODS: A panel of 51 invited medical oncologists and urologists convened in May of 2021 with the aim of discussing and providing recommendations regarding the most relevant issues concerning staging methods, antineoplastic therapy, osteoclast-targeted therapy, and patient follow-up in nmCRPC. Panel members considered the available evidence and their practical experience to address the 73 multiple-choice questions presented. RESULTS: Key recommendations and findings include the reliance on prostate-specific antigen doubling time for treatment decisions, the absence of a clear preference between conventional and novel (i.e., positron-emission tomography-based) imaging techniques, the increasing role of ARSis in various settings, the general view that ARSis have similar efficacy. Panelists highlighted the slight preference for darolutamide, when safety is of greater concern, and a continued need to develop high-level evidence to guide the intensity of follow-up in this subset of prostate cancer. DISCUSSION: Despite the limitations associated with a consensus panel, the topics addressed are relevant in current practice, and the recommendations can help practicing clinicians to provide state-of-the-art treatment to patients with nmCRPC in Brazil and other countries with similar healthcare settings.

Intrinsic doping limitations in inorganic lead halide perovskites.

Inorganic halide perovskites (HP's) of the CsPbX3 (X = I, Br, Cl) type have reached prominence in photovoltaic solar cell efficiencies, leading to the expectation that they are a new class of semiconductors relative to the traditional ones. Peculiarly, they have shown an asymmetry in their ability to be doped by holes vs. electrons. Indeed, both structural defect-induced doping as well as extrinsic impurity-induced doping strangely often result in HP's in a unipolar doping (dominantly p-type) with low free carriers' concentration. This raises the question whether such doping limitations presents just a temporary setback due to insufficient optimization of the doping process, or perhaps this represents an intrinsic, physically-mandated bottleneck. In this paper we study three fundamental Design Principles (DP's) for ideal doping, applying them via density functional doping theory to these HP's, thus identifying the violated DP that explains the doping limitations and asymmetry in these HP's. Here, the target DP are: (i) requires that the thermodynamic transition level between different charge states induced by the dopants must ideally be energetically shallow both for donors (n-type) or acceptors (p-type); DP-(ii) requires that the 'Fermi level pinning energies' for electrons E(n)pin and holes E(p)pin (being the limiting value of the Fermi level before a structural defect that compensate the doping forms spontaneously) should ideally be located inside the conduction band for n-type doping and inside the valence band for p-type doping. DP-(iii) requires that the doping-induced shift in equilibrium Fermi energy ΔE(n)F towards the conduction band for n-type doping (shift of ΔE(p)F towards the valence band, for p-type doping) to be sufficiently large. We find that, even though in HP's based on Br and Cl there are numerous shallow level dopants that satisfy DP-(i), in contrast DP-(ii) is satisfied only for holes and DP-(iii) fails for both holes and electrons, being the ultimate bottleneck for the n-type doping in Iodide HP's. This suggests an intrinsic mechanism for doping limitations in this class of semiconductors in terms of recognized physical mechanisms.

Bulk Rashba Effect Splitting and Suppression in Polymorphs of Metal Iodine Perovskites.

We quantified the bulk Rashba splitting and suppression in polymorphs of MA(Pb, Sn, Ge, or Si)I3 perovskites. The low-computational-cost DFT-1/2 quasiparticle correction was performed for all structures, combined with the inclusion of spin-orbit coupling (SOC) effects. The presence of SOC and symmetry breaking from the metal off-centering octahedral distortion are indispensable and essential conditions for Rashba splitting, whose magnitude emerges from the Pb → Si sequence. Additionally, the quasiparticle correction provides energy bandgaps for MAPbI3 (cubic, tetragonal, and orthorhombic), MASnI3 (cubic and tetragonal), and MAGeI3 (cubic) that are in outstanding agreement with experimental results. However, while gap energies are yielded collaboratively from the metal off-centering and relative octahedral tiltings, the bulk Rashba suppression is reached for metal on-centering (octahedral platonic-like) configurations that are thermodynamically stable even when the charge polarization is kept invariant among metal-I bonds in the polymorphs.

Unique Surface Enhanced Raman Scattering Substrate for the Study of Arsenic Speciation and Detection.

In this study, a three-dimensional surface enhanced Raman scattering (SERS) substrate comprised of silver coated gold nanorods (Ag/AuNRs) decorated on electrospun polycaprolactone (PCL) fibers has been applied,  for the first time, to quantitative analytical measurements on various arsenic species: p-arsanilic acid ( pAsA), roxarsone (Rox), and arsenate (AsV), with a demonstrated sensitivity below 5 ppb. AsV detection in a solution of common salt ions has been demonstrated, showing the tolerance of the substrate to more complex environments. pAsA adsorption behavior on the substrate surface has been investigated in detail using these unique SERS substrates. Calculations based on density functional theory (DFT) support the spectral observation for pAsA. This substrate also has been shown to serve as a platform for in situ studies of arsenic desorption and reduction. This SERS substrate is potentially an excellent environmental sensor for both fundamental studies and practical applications.

Optical and fundamental band gaps disparity in transparent conducting oxides: new findings for the [Formula: see text] and [Formula: see text] systems.

The optical band gap, extracted from absorption measurements, defines the figure of merit for transparent conducting oxides (TCOs). In many oxides, such as [Formula: see text] or [Formula: see text], inversion symmetry introduces a selection rule that blocks transitions from the valence-band maximum to the conduction-band minimum. This raises the absorption threshold and enlarges the optical gap relative to the fundamental band gap. Here, we present density-functional computations identifying two optical gaps, either of which can be detected, depending on the optical light intensity. Under strong illumination, weak transitions from [Formula: see text]-points near the valence-band maximum contribute significantly to the absorption spectrum and define an optical gap matching the fundamental gap. Low optical intensities by contrast give prominence to the large optical gap determined by the selection rule. While experimental conditions have favored observation of the former optical gap in [Formula: see text], in contrast, absorption measurements in [Formula: see text] have focused on the latter. Our findings explain the disparity between the optical and fundamental gaps in bixbyite [Formula: see text] and predict that, measured under low illumination, the optical gap for rutile [Formula: see text] will increase, from 3.60 eV to 4.34 eV.