Colloidal Quantum Dots…

FIG. 1.(a) Schematic of La Mer and Dinegar’s model for the synthesis of monodispersed CQDs. (b) Representation of the apparatus employed for CQD synthesis. Reproduced with permission from Murray et al., Annu. Rev. Mater Res. 30(1), 545–610 (2000). Copyright 2000 Annual Reviews.

Topics: Energy, Materials Science, Nanotechnology, Quantum Mechanics, Solar Power

ABSTRACT
Solution-processed colloidal quantum dot (CQD) solar cells are lightweight, flexible, inexpensive, and can be spray-coated on various substrates. However, their power conversion efficiency is still insufficient for commercial applications. To further boost CQD solar cell efficiency, researchers need to better understand and control how charge carriers and excitons transport in CQD thin films, i.e., the CQD solar cell electrical parameters including carrier lifetime, diffusion length, diffusivity, mobility, drift length, trap state density, and doping density. These parameters play key roles in determining CQD thin film thickness and surface passivation ligands in CQD solar cell fabrication processes. To characterize these CQD solar cell parameters, researchers have mostly used transient techniques, such as short-circuit current/open-circuit voltage decay, photoconductance decay, and time-resolved photoluminescence. These transient techniques based on the time-dependent excess carrier density decay generally exhibit an exponential profile, but they differ in the signal collection physics and can only be used in some particular scenarios. Furthermore, photovoltaic characterization techniques are moving from contact to non-contact, from steady-state to dynamic, and from small-spot testing to large-area imaging; what are the challenges, limitations, and prospects? To answer these questions, this Tutorial, in the context of CQD thin film and solar cell characterization, looks at trends in characterization technique development by comparing various conventional techniques in meeting research and/or industrial demands. For a good physical understanding of material properties, the basic physics of CQD materials and devices are reviewed first, followed by a detailed discussion of various characterization techniques and their suitability for CQD photovoltaic devices.

Advanced characterization methods of carrier transport in quantum dot photovoltaic solar cells, Lilei Hu, Andreas Mandelis, Journal of Applied Physics

What They Meant…

Image Source: 100 photos, Time.com, Emmett Till

Topics: Civics, Civil Rights, Democratic Republic, Existentialism, Fascism, Human Rights

100 photos, Time: In August 1955, Emmett Till, a black teenager from Chicago, was visiting relatives in Mississippi when he stopped at Bryant’s Grocery and Meat Market. There he encountered Carolyn Bryant, a white woman. Whether Till really flirted with Bryant or whistled at her isn’t known. But what happened four days later is. Bryant’s husband Roy and his half-brother, J.W. Milam, seized the 14-year-old from his great-uncle’s house. The pair then beat Till, shot him, and strung barbed wire and a 75-pound metal fan around his neck, and dumped the lifeless body in the Tallahatchie River. A white jury quickly acquitted the men, with one juror saying it had taken so long only because they had to break to drink some pop. When Till’s mother Mamie came to identify her son, she told the funeral director, “Let the people see what I’ve seen.” She brought him home to Chicago and insisted on an open casket. Tens of thousands filed past Till’s remains, but it was the publication of the searing funeral image in Jet, with a stoic Mamie gazing at her murdered child’s ravaged body, that forced the world to reckon with the brutality of American racism. For almost a century, African Americans were lynched with regularity and impunity. Now, thanks to a mother’s determination to expose the barbarousness of the crime, the public could no longer pretend to ignore what they couldn’t see.

I am a child of “forced bussing,” emphasized by the dominant culture of North Carolina in 1971, when 1954’s Supreme Court Brown vs. Board of Education Decision, and “all deliberate speed” reached my municipality. I remember being nine years old, riding on buses at zero-dark-thirty in the morning to Rural Hall Elementary for the fourth grade, a limited experiment in federally-mandated diversity. I traveled to was in what was then, the rich, white suburbs. Every time my friends and I got off buses, we were miles from our homes.

We generally stayed in clicks: black youths on one side of the cafeteria, white youths on the other. In the evenings, I remember watching local and national news where high school students brought chains, bats, and knives. I recall waiting for our powder keg to explode.

Then, we played a game of football during recess. I don’t know what “did it” for the girls, but boys covered in sweat, mud, and scrapes develop bonds that are hard to ignore. Thankfully, the powder keg never went off.

From Rural Hall, we were bussed back to East Winston-Salem at Fairview Elementary for fifth, and sixth grade. On to Mineral Springs Middle School for seventh, and eighth grade. Atkins, Carver, Hanes, and Paisley – traditionally, African American High Schools that reliably fed HBCUs – were “demoted” to ninth/tenth grade high schools, so that every student in the city would have the “benefit” of diplomas from the traditionally white high schools of North, East, Mount Tabor, and West.

The good news: most of the fourth graders that aged through this forced diversity got used to seeing people other than themselves. Star Trek was in syndication, and we were inspired by the vision of a future that at least our descendants would have their acts together, and learn, like we did to live together post-warp drive, or football.

The not-so-good news: There were quite a few interracial couples, which I had never seen before. Quite a few “Christian” Academies sprung up to sidestep what their parents saw as ungodly miscegenation. I haven’t kept contact with my former classmates from Rural Hall Elementary, Mineral Springs Middle School, Atkins High School, and North Forsyth High School. I can’t help but imagine that many of them on the other side of the cafeteria before our mud-soaked football games have returned to the other side, donned red hats, and QAnon paraphernalia.

There was a list of Emmett Tills before Emmett Till. The brutality visited upon his teenage body compared modernly to Trayvon Martin, Jordan Davis, Renisha McBride, Eric Garner, Sandra Bland, Ahmaud Aubrey, Breonna Taylor, and George Floyd. There are literally hundreds more. Many, like the Emmett Tills before Emmett Till, are unknown, unheard of: unlisted.

The times they want to return to wasn’t so much the president named Eisenhower versus Obama; white picket fences in Levittown’s, or affordable healthcare: “great again” is the ability to reign terror, and murder on an entire community – black, brown, LGBT, women, with absolute impunity. They made that QUITE clear on January 6, 2021.

Every significant group that has had knees on their necks, oppressed by the dominant group since Plymouth Rock took inspiration from the efforts that started post-1865, to this present political darkness. It will continue until E Pluribus Unum isn’t just a quaint Latin phrase. We cannot be a democratic republic, AND a nihilistic, fascist dictatorship.

Their “great again” wish is that Mother Till hadn’t opened that casket.

We are NOT going back! Black lives, and democracy, matter.

The Black Edison…

Garrett A. Morgan (1877–1963), American inventor and community leader. Credit: Alamy

Topics: African Americans, Civics, Civil Rights, History, Human Rights

“If you can control a man’s thinking you do not have to worry about his action. When you determine what a man shall think you do not have to concern yourself about what he will do. If you make a man feel that he is inferior, you do not have to compel him to accept an inferior status, for he will seek it himself. If you make a man think that he is justly an outcast, you do not have to order him to the back door. He will go without being told; and if there is no back door, his very nature will demand one.” Dr. Carter Godwin Woodson, The Mis-Education of the Negro

*****

Just before midnight at the close of a hot summer day in 1916, a natural gas pocket exploded 120 feet beneath the waves of Lake Erie. It happened during work on Cleveland’s newest waterworks tunnel, a 10-foot-wide underwater artery designed to pull in water from about five miles out, beyond the city’s polluted shoreline. The blast left twisted conduit pipes littering the tunnel floor and tore up railroad tracks inside the corridor, with noxious smoke curling off the rubble. When the dust settled, 11 tunnel workers were dead.

Two rescue parties entered the tunnel searching for survivors. But they lacked proper safety equipment for the smoke and fumes; 11 of the 18 rescuers died. Some 11 hours later, desperate to save anyone still alive, the Cleveland Police turned to Garrett A. Morgan—a local inventor who called himself “the Black Edison”—and the gas mask he had patented two years earlier.

“He rustled his brother Frank,” says the inventor’s granddaughter, Sandra Morgan. “They threw a bunch of gas masks in the car—remember, they were selling these things—and in their pajamas, drove down to the lakefront.”

Some five years later, in the early 1920s, the inventor witnessed a horrific accident between an automobile and a horse-drawn cart at an intersection. Once again, his ingenuity kicked in. Before Morgan, traffic signals only had two positions: stop and go. “My grandfather’s great improvement,” Sandra says, “was the ‘all hold’—what is now the amber light.” Morgan patented the three-position traffic signal in 1923 and soon sold the idea to General Electric for $40,000 (the equivalent of about $610,000 today). He purchased 250 acres later that year in Wakeman, Ohio, and transformed it into an African American country club complete with a party room and dance hall.

*****

“The mere imparting of information is not education. ” Dr. Carter G. Woodson

Black Inventor Garrett Morgan Saved Countless Lives with Gas Mask and Improved Traffic Lights, Leo DeLuca, Scientific American

Snapping Polymer Discs…

Thin polymer discs self-propel by repeated “snapping” motions. Credit: Yongjin Kim, UMass Amherst

Topics: Chemistry, Polymer Science, Materials Science, Research

A polymer-based gel made by researchers in the US and inspired by the Venus flytrap plant can snap, jump and “reset” itself autonomously. The new self-propelled material might have applications in micron-sized robots and other devices that operate without batteries or motors.

“Many plants and animals, especially small ones, use special parts that act like springs and latches to help them move really fast, much faster than animals with muscles alone,” explains team leader Alfred Crosby, a professor of polymer science and engineering in the College of Natural Sciences at UMass Amherst. “The Venus flytraps are good examples of this kind of movement, as are grasshoppers and trap-jaw ants in the animal world.”

Snapping instabilities
The Venus flytrap plant works by regulating the way its turgor pressure – that is, the swelling produced as stored water pushes against a plant cell wall – is distributed through its leaves. Beyond a certain point, this swelling leads to a condition known as a snapping instability, where the tiny additional pressure of a fly’s footsteps is enough to cause the plant to snap shut. The plant then automatically regenerates its internal structures in readiness for its next meal.

Polymer gels snap and jump on their own, Isabelle Dumé, Physics World

Einsteinium Chemistry…

Topics: Chemistry, Einstein, Materials Science, Research

To date, researchers have created more than two dozen synthetic chemical elements that don’t exist naturally on Earth. Neptunium (atomic number Z = 93) and plutonium (Z = 94), the first two artificial elements after naturally occurring uranium, are produced in nuclear reactors by the thousands of kilograms. But the accessibility of transuranic elements drops quickly with Z: Einsteinium (Z = 99) can be made only in microgram quantities in specialized laboratories, fermium (Z = 100) is produced by the picogram and has never been purified, and all elements after that are made just one atom at a time.

There are ways to probe the atomic properties of elements produced atom by atom (see, for example, Physics Today, June 2015, page 14). But when it comes to the traditional way of investigating how atoms behave—mixing them with other substances in solution to form chemical compounds—Es is effectively the end of the periodic table.

Now Rebecca Abergel (head of Lawrence Berkeley National Laboratory’s heavy element chemistry program) and her colleagues have performed the most complicated and informative Es chemistry experiment to date. They chose to react Es with a so-called octadentate ligand—a single organic molecule, held together by the backbone shown in blue, that wraps around a central metal atom and binds to it from all sides—to create the molecular structure shown in the figure. In their previous work, Abergel and colleagues used the same ligand to study transition metals, lanthanides, and lighter actinides. When they were fortunate enough to acquire a few hundred nanograms of Es from Oak Ridge National Laboratory, they used it on that as well.

Einsteinium chemistry captured, Johanna L. Miller, Physics Today

Touchdown…

Topics: Mars, NASA, Perseverance, Space Exploration, Spaceflight

Editor’s Note: This release was updated on Feb. 22 to correct the metric unit for the speed at which the rover’s wheels made contact with the surface to kph.

New video from NASA’s Mars 2020 Perseverance rover chronicles major milestones during the final minutes of its entry, descent, and landing (EDL) on the Red Planet on Feb. 18 as the spacecraft plummeted, parachuted, and rocketed toward the surface of Mars. A microphone on the rover also has provided the first audio recording of sounds from Mars.

NASA’s Mars Perseverance Rover Provides Front-Row Seat to Landing, First Audio Recording of Red Planet

Splitting Babies, Washing Hands…

Pop Culture Guy: Foghorn Leghorn

Topics: Civics, Civil Rights, Existentialism, Fascism, Human Rights, Politics

To split the baby is a reference to a story in the Old Testament in Kings 3:5-14, regarding a decision of Solomon that shows his wisdom when given a difficult task. Solomon as king was often asked to judge between people with difficult problems, and his solutions were accounted as very wise. The term is often used to describe an unreasonable solution that may be used as a way to find an underlying truth.

In Kings, two women approach Solomon, both claiming to be the mother of the same baby. In fact, one woman has smothered her own child in her sleep and has taken the child of another woman with whom she shares a home. Upon waking, the mother of the living baby finds she is holding the dead child, who she knows is not hers. Since she cannot convince the mother of the dead child to give her back her child, they go to Solomon for judgment.

Solomon’s solution is fairly unique. He hears both sides, which are identical, and decides that the best course is to cut the baby in half so both mothers will have a share. To do this, however, means to kill the child. The mother who has already lost a child is happy with the solution, but the real mother cries out and begs Solomon to let the other woman raise her child alive.

When the real mother protests the solution and is willing to give up her rights as a mother to preserve the life of her child, Solomon hands the baby to her.

What does It Mean to “Split the Baby”? Tricia Christensen, Wise Geek

What did it mean? Pontius Pilate was the Roman procurator (governor) of Judaea living in Jerusalem during the trial of Jesus. According to the story, he washed his hands to indicate that he believed Jesus was innocent of any capital crime – if he was killed – it wasn’t on him.

A famous idiom from Matthew 27:24

The prosecution put on a clinic in the Well of the Senate in their closing remarks. Every avenue to derail the trial on “procedure,” or “constitutional norms” was deftly batted away. It helps when the prosecution is playing seven-dimensional chess, and the defense team of Foggy Foghorn Leghorn, and Rage Elmer Fudd, is playing jacks.

The former Party of Lincoln has ridden this Kraken before the Orange Orangutan. Roger Ailes and talk radio proto Karl Rove, “created their own reality” in a Rush Limbaugh, cigar-chomping, racist ranting clones (because you don’t need talent if you get a raging crowd buying your product), against the libs, Feminazis, and cooties. For forty-one years, from Reagan to Orange Satan, they have gaslighted their constituents, blamed every convenient “other” they could label and shoveled money uphill like a Hoover vacuum to their one percent benefactors. They have no intention of getting off this bucking steer in the right-wing rodeo, otherwise, like rodeo clowns, they might get skewered by the bull.

I don’t expect there to be enough votes to convict him. It will be just shy of sixty-seven. I hope to be pleasantly surprised. The arcane rules of the Senate even after the off possibility of getting to sixty-seven, then have to take a simple majority vote to remove him from running again for office. He will be fatter, four years older, more insane, and publicly incontinent in 2024 (he wears Adult Depends now). Entropy can save us, or his criminal trials for state crimes in New York, and Georgia can put him in a wardrobe matching his fake, and grotesque spray tan. Cruz and Holley are salivating at this possibility.

They are splitting the baby: forty or so white republicans, and their mascot, Tim Scott, will vote again to acquit a criminal. Not because they’re no longer the “party of law, and order.” Not because the Party of Reagan was any greater: he started his campaign BLOCKS away from the death site of Chaney, Goodman, and Schwerner; he spoke openly about Welfare Queens, Young Bucks, and African Monkeys. Doofus Gambino is the end of Entropy: over a long period of time, any system goes from order to chaos. Forty-plus one poodle are looking forward to the next midterm, the next election, the next voter suppression, and now added to the quiver: the next insurrection, Like see no evil, hear no evil, speak no evil monkeys, they will ignore it, and use it as a tool if they lose future elections.

The Neo-Confederates are self-immolating, and not for some noble protest, but to maintain power at the expense of the republic. They are the party whose defense will relitigate “WHATABOUTISM” with Antifa (anti-fascists), Benghazi (might as well), and Black Lives Matter (because, they don’t). Foggy Fog, and Rage Elmer will unimpressively rest today. Gaslighting and created realities will blow them up to the high crest peak of BS mountain. Rage will then observe the Sabbath at sundown.

They are the party of white nationalists. They are the party screaming the N-word at Capital Police during the insurrection. They are the party of smeared feces and urinated Capitol halls. They are the party of Camp Auschwitz T-Shirts: Work Brings Freedom. They are the party of the Battle Ensign of Robert E. Lee (NEVER call it the Confederate Flag) flying at the Capitol, something not accomplished during the Civil War. They are the party of Ukraine and Georgia election interference “perfect” phone calls. They are the party that would sacrifice their own sycophant Vice President Mike Pence, and execute the first and only female Speaker of the House of Representatives, Nancy Pelosi. They are the party of Vice President of the treasonous Confederacy, Alexander M. Stephens, and the “Cornerstone Speech”:

“Our new government is founded upon exactly the opposite idea; its foundations are laid, its corner-stone rests, upon the great truth that the negro is not equal to the white man; that slavery subordination to the superior race is his natural and normal condition. This, our new government, is the first, in the history of the world, based upon this great physical, philosophical, and moral truth.” Cornerstone Speech

They have not wavered from this mentality. It’s been taught over and over, father to son, mother to daughter. The first gaslighting being the “lost cause” narrative lie, metastasizing to the inherited inferiority narrative shoveled at all of us, the proto version of birtherism, stolen from Orly Taitz. This “alternative fact” was amplified by a failed businessman, a faux billionaire that [probably] had Russian prostitutes urinate in a bed of the black president and first lady he hated with every fiber of his dark soul, that knows no love.

Eighty-one percent of white evangelicals left any allegiance they ever had to brown-skinned, Palestinian prophets, and voted for this Antichrist.

They, therefore, cannot be called Republicans any longer: they are fascists.

Tick Tock…

An unarmed Minuteman III intercontinental ballistic missile launches during an operational test from Vandenberg Air Force Base, California, on February 25, 2016. (Kyla Gifford / US Air Force)

Topics: Existentialism, Global Warming, Nuclear Power

Please understand my perspective: I am an Air Force veteran, and I think this is over-the-top. Related post: It is 100 seconds to midnight.

America is building a new weapon of mass destruction, a nuclear missile the length of a bowling lane. It will be able to travel some 6,000 miles, carrying a warhead more than 20 times more powerful than the atomic bomb dropped on Hiroshima. It will be able to kill hundreds of thousands of people in a single shot.

The US Air Force plans to order more than 600 of them.

On September 8, the Air Force gave the defense company Northrop Grumman an initial contract of $13.3 billion to begin engineering and manufacturing the missile, but that will be just a fraction of the total bill. Based on a Pentagon report cited by the Arms Control Association Association and Bloomberg News, the government will spend roughly $100 billion to build the weapon, which will be ready to use around 2029.

To put that price tag in perspective, $100 billion could pay 1.24 million elementary school teacher salaries for a year, provide 2.84 million four-year university scholarships, or cover 3.3 million hospital stays for covid-19 patients. It’s enough to build a massive mechanical wall to protect New York City from sea level rise. It’s enough to get to Mars.

Why is America getting a new $100 billion nuclear weapon? Bulletin of the Atomic Scientists

Kondo Mimic…

Illustration showing the atomic tip of a scanning tunneling microscope while probing a metal surface with a cobalt atom positioned on top. A characteristic dip in the measurement results is found on surfaces made of copper as well as of silver and gold. Courtesy: Forschungszentrum Jülich

Topics: Magnetism, Materials Science, Nanotechnology

A new type of quasiparticle – dubbed the “spinaron” by the scientists who discovered it – could be responsible for a magnetic phenomenon that is usually attributed to the Kondo effect. The research, which was carried out by Samir Lounis and colleagues at Germany’s Forschungszentrum Jülich, casts doubt on current theories of the Kondo effect, and could have implications for data storage and processing based on structures such as quantum dots.

The electrical resistance of most metals decreases as the temperature drops. Metals containing magnetic impurities, however, behave differently. Below a certain threshold temperature, their electrical resistance increases rapidly, and continues to increase as the temperature drops further. First spotted in the 1930s, this phenomenon became known as the Kondo effect after the Japanese theoretical physicist Jun Kondo published an explanation for it in 1964.

New quasiparticle may mimic Kondo-effect signal, Isabelle Dumé, Physics World

Well Deserved…

Anthony Fauci has advised seven presidents on public health, most recently serving as chief medical advisor to President Joe Biden. | NIAID

Topics: Biology, COVID-19, Research, Science

Anthony Fauci – director of the National Institute of Allergy and Infectious Diseases, an expert on HIV and immunoregulation, and the de facto public face of a science-based recovery from COVID-19 – has been named the winner of the 2021 Philip Hauge Abelson Prize, awarded annually by the American Association for the Advancement of Science to a scientist or public servant who has contributed significantly to the advancement of science in the United States.

Fauci is “an outstanding scientist with more than a thousand publications” and “an exceptional public servant, having been at the forefront of the world’s efforts to combat diverse infectious diseases for over 40 years,” wrote Alan Leshner, former chief executive officer of AAAS, in nominating Fauci for the prize. The prize committee cited Fauci’s “extraordinary contributions to science and medicine” and his service that has shaped research and public policy.

Anthony Fauci to Receive 2021 AAAS Abelson Prize, Andrea Korte, American Association for the Advancement of Science