Carbon dots (CDots) are a promising biocompatible nanoscale source of light, yet the origin their emission remains under debate. Here, we show that all distinctive optical properties CDots, including giant Stokes shift photoluminescence and strong dependence color on excitation wavelength, can be explained by linear response partially sp2-hybridized carbon domains located surface CDots' sp3-hybridized amorphous cores. Using simple quantum chemical approach, domain hybridization factor...

Two-dimensional (2D) nanomaterials have been intensively investigated due to their interesting properties and range of potential applications. Although most research has focused on graphene, atomic layered transition metal dichalcogenides (TMDs) particularly MoS2 gathered much deserved attention recently. Here, we report the induction chirality into 2D chiral by carrying out liquid exfoliation in presence ligands (cysteine penicillamine) water. This processing resulted exfoliated nanosheets...

The availability of carbon dots (CDots) with bright red photoluminescence (PL) would significantly broaden the range their biological and optoelectronic applications. We present a theoretical model that predicts amino functionalization CDots not only shifts PL to longer wavelengths but also preserves large oscillator strengths fundamental radiative transitions CDots. considers optical response amino-functionalized determined by molecule-like subunits polycyclic aromatic hydrocarbons one,...

The optical properties of monolayer and bilayer transition metal dichalcogenide semiconductors are governed by excitons in different spin valley configurations, providing versatile aspects for van der Waals heterostructures devices. We present experimental theoretical studies exciton energy splittings external magnetic field neutral charged WSe$_2$ crystals embedded a effect device active doping control. develop methods to calculate the $g$-factors from first principles tight-binding all...

Abstract Fast and reliable separation of enantiomers chiral nanoparticles requires elimination all the forces that are independent nanoparticle handedness creation a sufficiently strong force either pushes different in opposite directions or delays diffusion one them with respect to other. Here we show how construct such completely optical using two counterpropagating circularly polarized plane waves helicities. We then explore capabilities related enantioseparation method by analytically...

Relatively weak red photoluminescence of carbon dots (CDots) is a major challenge on the way to their successful implementation in biological and optoelectronic devices. We present theoretical analysis interaction among surface emission centers CDots, showing that it may determine efficiency CDots. Based previous experimental studies, assumed optical response CDots determined by molecule-like subunits polycyclic aromatic hydrocarbons (PAHs) attached CDots' surface. Three characteristic types...

Armchair graphene nanoribbons are a highly promising class of semiconductors for all-carbon nanocircuitry. Here, we present new perspective on their electronic structure from simple model Hamiltonians and ab initio calculations. We focus specific set width $n=3p+2$, where $n$ is the number carbon atoms across nanoribbon axis $p$ positive integer. demonstrate that energy-gap opening in these originates breaking previously unidentified hidden symmetry by long-ranged hopping $\ensuremath{\pi}$...

Understanding the photosensitization mechanisms in Yb3+-doped perovskite nanocrystals is crucial for developing their anticipated photonic applications. Here, we address this question by investigating near-infrared photoluminescence of mixed-halide CsPbClxBr3–x as a function temperature and revealing its strong dependence on stoichiometry host matrix. To explain observed experimental trends, developed theoretical model which energy transfer from matrix to Yb3+ ions occurs through...

Atomically thin crystals hosting flat electronic bands have recently been identified as a rich playground for exploring and engineering strongly correlated phases. Yet, their variety remains limited, primarily to two-dimensional moiré superlattices. Here, we predict the formation of reversible, electrically induced ultraflat π-electron magnetism in one-dimensional chevron graphene nanoribbons. Our ab initio calculations show that application transverse electric field these nanoribbons...

We examine the electronic structure of recently fabricated in-plane heterojunctions zigzag graphene nanoribbons embedded in hexagonal boron nitride. focus on hitherto unexplored interface configurations which both edges nanoribbon are bonded to same chemical species, either or nitrogen atoms. Using ab initio and mean-field Hubbard model calculations, we reveal emergence one-dimensional magnetic conducting channels at these interfaces. These originate from energy shift states that is induced...

Large surface-to-volume ratio, one-dimensional quantum confinement, and strong optical activity make chiral nanoscrolls ideal for the detection sensing of small molecules. Here, we present a simple physical model chiroptical phenomena in multilayered tapered semiconductor nanoscrolls. Our is based on linear transformation coordinates, which converts into flat but topologically distorted nanoplatelets whose properties can then be treated analytically. As an illustrative application example,...

We present a general approach to analyzing the optical activity of semiconductor nanocrystals chiral shapes. By using coordinate transformation that turns nanocrystal into nanocuboid, we calculate rotatory strengths, dissymmetry factors, and peak values circular dichroism (CD) signal upon intraband transitions inside nanocrystal. It is shown atomic roughness surface can result in strengths as high 10-36 erg×cm3 CD signals about 0.1 cm-1 for typical densities 1016 cm-3. The developed may...

Twisted bilayer graphene (TBG) is a two-dimensional chiral material whose optical activity remarkably strong for its atomic thickness. While the properties of TBG are currently well understood, quantum dots (QDs) made has not been analyzed so far. Here, we comprehensively analyze QDs with hexagonal, triangular, and rhomboid symmetries. We show that dissymmetry factors can reach 10–2, greatly exceeding semiconductor small molecules. The due to out-of-plane polarized transitions pz electrons...

We develop a general theory of optical activity semiconductor nanocrystals whose chirality is induced by small perturbation their otherwise achiral electronic subsystems. The described using the quantum-mechanical expressions for rotatory strengths and dissymmetry factors introduced Rosenfeld. show that optically active transitions are decomposed on electric dipole magnetic contributions, which correspond to between unperturbed quantum states. Remarkably, while two kinds same order...

Abstract The ability to induce optical activity in nanoparticles and dynamically control its strength is of great practical importance due potential applications various areas, including biochemistry, toxicology, pharmaceutical science. Here we propose a new method creating originally achiral quantum nanostructures based on the mixing their energy states different parities. can be achieved by selective excitation specific or via perturbing all controllable fashion. We analyze general...

Abstract Controlling the strength of enantioselective interaction chiral inorganic nanoparticles with circularly polarized light is an intrinsically interesting subject contemporary nanophotonics. This relatively weak, because chirality scale much smaller than optical wavelength. Here we theoretically demonstrate that ion doping provides a powerful tool engineering and enhances activity semiconductor nanocrystals. We show by carefully positioning ionic impurities inside nanocrystals, one can...

We theoretically study the broadening of optical absorption spectra monodisperse ensembles randomly oriented nanorods and nanoplatelets exposed to a static electric field. It is found that weaker quantum confinement inside results in much stronger field impact on their than nanorods. The most notable manifestation this widths lines nanoplatelets’ peak as functions strength. Both maximal corresponding optimal strengths are decrease with largest dimensions nanoplatelets. In sharp contrast...

We develop a simple quantum-mechanical theory of interband absorption by semiconductor nanocrystals exposed to dc electric field. The is based on the model noninteracting electrons and holes in an infinitely deep quantum well describes all major features electroabsorption, including Stark effect, Franz-Keldysh field-induced spectral broadening. It applicable different shapes dimensions (quantum dots, nanorods, nanoplatelets), will prove useful modeling design electrooptical devices ensembles...

We present rigorous analysis of optical activity chiral semiconductor gammadions whose chirality in three dimensions is caused by the nonuniformity thickness transverse plane. It shown that such not only distinguish between two circular polarizations upon scattering and reflection light, like all two-dimensional nanostructures with planar do, but also exhibit dichroism circularly polarized luminescence. Chiral charge carriers are mostly confined to arms found feature both high dissymmetry...

Graphene nanoribbons are widely regarded as promising building blocks for next-generation carbon-based devices. A critical issue to their prospective applications is whether electronic structure can be externally controlled. Here, we combine simple model Hamiltonians with extensive first-principles calculations investigate the response of armchair graphene transverse electric fields. Such fields achieved either upon laterally gating nanoribbon or incorporating ambipolar chemical codopants...

The determination of physical mechanisms governing photoluminescence (PL) carbon dots (CDots) is required for fabrication CDots with desired optical properties. Using the density functional theory, we comprehensively analyze how changes in structure molecular centers during synthesis blue-emissive affect their Our calculations predict a pronounced red shift PL peak and decrease intensity by up to 2 orders magnitude when monomer-like are replaced covalent or noncovalent dimers fluorophore...

Half-metals have been envisioned as active components in spintronic devices by virtue of their completely spin-polarized electrical currents. Actual materials hosting half-metallic phases, however, remain scarce. Here, we predict that recently fabricated heterojunctions zigzag nanoribbons embedded two-dimensional hexagonal boron nitride are half-semimetallic, featuring fully Dirac points at the Fermi level. The half-semimetallicity originates from transfer charges to graphene nanoribbon....

Here we review our three recently developed analytical models describing the intraband optical activity of semiconductor nanocrystals, which is induced by screw dislocations, ionic impurities, or irregularities nanocrystal surface. The predict that nanocrystals can exhibit strong upon transitions and have large dissymmetry magnetic-dipole absorption. be used to interpret experimental circular dichroism spectra advance existing techniques enantioseparation, biosensing, chiral chemistry.

The advancement of optical technology demands the development chiral nanostructures with a strong dissymmetry response. Here, we comprehensively analyze properties circular twisted graphene nanostrips, particular emphasis on case Möbius nanostrip. We use method coordinate transformation to analytically model electronic structure and spectra while employing cyclic boundary conditions account for their topology. It is found that factors nanostrips can reach 0.01, exceeding typical small...

Quantum confinement and collective excitations in perovskite quantum-dot (QD) supercrystals offer multiple benefits to the light emitting solar energy harvesting devices of modern photovoltaics. Recent advances fabrication technology low dimensional perovskites has made production such a reality created high demand for modelling excitonic phenomena inside them. Here we present rigorous theory Frenkel excitons lead halide QD with square Bravais lattice. The shows that support three bright...