The electronic and optical properties of close packed cadmium selenide quantum dot solids

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.Includes bibliographical references (p. 165-168).by Cherie Renee Kagan.Ph.D

Ambipolar transport in solution-deposited pentacene transistors enhanced by molecular engineering of device contacts

We report ambipolar transport in bottom gold contact, pentacene field-effect transistors (FETs) fabricated by spin-coating and thermally converting its precursor on a benzocyclobutene/SiO2 gate dielectric with chemically modified source and drain electrodes. A wide range of aliphatic and aromatic self-assembled thiolate monolayers were used to derivatize the electrodes and all enhanced electron and hole currents, yet did not affect the observable thin film morphology. Hole and electron mobilities of 0.1–0.5 and 0.05–0.1 cm2 / V s are achieved, though the threshold for electron transport was \u3e80 V. These ambipolar FETs are used to demonstrate inverters with gains of up to 94

Photocatalytic Hydrogen Evolution from Sub-Stoichiometric Colloidal WO3-xNanowires

We report direct photocatalytic hydrogen evolution from substoichiometric highly reduced tungsten oxide (WOx) nanowires (NWs) using sacrificial alcohol. WOx NWs are synthesized via nonaqueous colloidal synthesis with a diameter of about 4 nm and an average length of about 250 nm. As-synthesized WOx NWs exhibit a broad absorption across the visible to infrared regions attributed to the presence of oxygen vacancies. The optical band gap is increased in these WOx NWs compared to stoichiometric bulk tungsten oxide (WO3) powders as a result of the Burstein\u2013Moss shift. As a consequence of this increase, we demonstrate direct photocatalytic hydrogen production from WOx NWs through alcohol photoreforming. The stable H2 evolution on platinized WOx NWs is observed under conditions in which platinized bulk WO3 and bulk WO2.9 powders either do not show activity or show very low rates, suggesting that increased surface area and specific exposed facets are key for the improved performance of WOx NWs. This work demonstrates that control of size and composition can lead to unexpected and beneficial changes in the photocatalytic properties of semiconductor materials

Nanodiamond emulsions for enhanced quantum sensing and click-chemistry conjugation

Nanodiamonds containing nitrogen-vacancy (NV) centers can serve as colloidal quantum sensors of local fields in biological and chemical environments. However, nanodiamond surfaces are challenging to modify without degrading their colloidal stability or the NV center's optical and spin properties. Here, we report a simple and general method to coat nanodiamonds with a thin emulsion layer that preserves their quantum features, enhances their colloidal stability, and provides functional groups for subsequent crosslinking and click-chemistry conjugation reactions. To demonstrate this technique, we decorate the nanodiamonds with combinations of carboxyl- and azide-terminated amphiphiles that enable conjugation using two different strategies. We study the effect of the emulsion layer on the NV center's spin lifetime, and we quantify the nanodiamonds' chemical sensitivity to paramagnetic ions using $T_1$ relaxometry. This general approach to nanodiamond surface functionalization will enable advances in quantum nanomedicine and biological sensing.Comment: 52 pages, 42 figures (main text plus supplementary information

Оценка территориальных рисков возникновения ЧС в лесном массиве

Объект исследования: лесной массив в Томской области. Цель работы - оценка территориальных рисков возникновения чрезвычайных ситуации в лесном массиве. Проведен аналитический обзор литературы по теме исследования, построено дерево причин возникновения лесного пожара, поставлены эксперименты по определению температуры самовозгорания образца "ягеля".Research object: woodland in the Tomsk region. The purpose of the work is to assess the territorial risks of emergencies in the forest. An analytical review of the literature on the research topic was carried out, a tree of the causes of a forest fire was built, and experiments were carried out to determine the temperature of spontaneous combustion of a reindeer moss sample

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead