Formation of Corrugated n = 1 2D Tin Iodide Perovskites and Their Use as Lead-Free Solar Absorbers

Major strides have been made in the development of materials and devices based around low-dimensional hybrid group 14 metal halide perovskites. Thus far, this work has mostly focused upon compounds containing highly toxic Pb, with the analogous less toxic Sn materials being comparatively poorly evolved. In response, the study herein aims to (i) provide insight into the impact of templating cation upon the structure of n = 1 2D tin iodide perovskites (where n refers to the number of contiguous two-dimensional (2D) inorganic layers, i.e., not separated by organic cations), and (ii) examine their potential as light absorbers for photovoltaic (PV) cells. It was discovered through systematic tuning of organic dications, that imidazolium rings are able to induce formation of (110)-oriented materials, including the examples of “3 × 3” corrugated Sn-I perovskites. This structural outcome is a consequence of a combination of supramolecular interactions of the two endocyclic N-atoms in the imidazolium functionalities with the Sn-I framework and the higher tendency of Sn2+ ions to stereochemically express their 5s2 lone pairs relative to the 6s2 electrons of Pb2+. More importantly, the resulting materials feature very short separations between their 2D inorganic layers with iodide–iodide (I···I) contacts as small as 4.174 Å, which is amongst the shortest ever recorded for 2D tin iodide perovskites. The proximate inorganic distances, combined with the polarizable nature of the imidazolium moiety, eases the separation of photogenerated charge within the materials. This is evident from the excitonic activation energies as low as 83(10) meV, measured for ImEA[SnI4]. When combined with superior light absorption capabilities relative to their lead congeners, this allowed fabrication of lead-free solar cells with incident photon-to-current and power conversion efficiencies of up to 70 % and 2.26 %, respectively, which are amongst the highest values reported for pure n = 1 2D group 14 metal halide perovskites. In fact, these values are superior to the corresponding lead iodide material, which demonstrates that 2D Sn-based materials have significant potential as less toxic alternatives to their Pb counterparts

Strategies for Controlled Placement of Nanoscale Building Blocks

The capability of placing individual nanoscale building blocks on exact substrate locations in a controlled manner is one of the key requirements to realize future electronic, optical, and magnetic devices and sensors that are composed of such blocks. This article reviews some important advances in the strategies for controlled placement of nanoscale building blocks. In particular, we will overview template assisted placement that utilizes physical, molecular, or electrostatic templates, DNA-programmed assembly, placement using dielectrophoresis, approaches for non-close-packed assembly of spherical particles, and recent development of focused placement schemes including electrostatic funneling, focused placement via molecular gradient patterns, electrodynamic focusing of charged aerosols, and others

Combining quick sequential organ failure assessment score with heart rate variability may improve predictive ability for mortality in septic patients at the emergency department

10.1371/journal.pone.0213445PLoS ONE143e021344

Prediction of adverse cardiac events in emergency department patients with chest pain using machine learning for variable selection

10.1186/1472-6947-14-75BMC Medical Informatics and Decision Making1417

Heart rate variability based machine learning models for risk prediction of suspected sepsis patients in the emergency department

10.1097/MD.0000000000014197Medicine (United States)986e1419

A novel cardiovascular risk stratification model incorporating ECG and heart rate variability for patients presenting to the emergency department with chest pain

10.1186/s13054-016-1367-5Critical Care20117

Validation of the mortality in emergency department sepsis (MEDS) score in a Singaporean cohort

10.1097/MD.0000000000016962Medicine (United States)9834e1696

The effect of availability of manpower on trauma resuscitation times in a Tertiary Academic Hospital

10.1371/journal.pone.0154595PLoS ONE115e015459

XAF1 promotes neuroblastoma tumor suppression and is required for KIF1B?-mediated apoptosis

10.18632/oncotarget.8748Oncotarget72334229-3423

Heart rate variability risk score for prediction of acute cardiac complications in ED patients with chest pain

10.1016/j.ajem.2013.05.005American Journal of Emergency Medicine3181201-1207AJEM