Extraordinary Photoluminescence Research Articles

Extraordinary photoexcitation of semimetal 1T'-MoTe2 inducing ultrafast charge transfer in lateral 2D homojunction

Exploring novel and more efficient photoexcitation transition mechanisms in two-dimensional transition metal dichalcogenides (TMDCs) is crucial for the advancement of high-performance optoelectronic devices. In this study, an extraordinary photoluminescence (PL) phenomenon is discovered that originates from a vertical transition between specific bands in the X-point energy valley of K-space in multilayer Weyl semi-metal monoclinic (1T') MoTe2 without a gap structure. This effective transition is independent of the bandgap and is unaffected by the number of layers in 1T'-MoTe2, breaking the limitations of traditional TMDCs semiconductor materials and promoting the development of advanced two-dimensional (2D) semimetal-based optoelectronic devices. In a lateral multilayer 1T'-MoTe2-2H hetero-phase homojunction, a record ultrafast transfer of photogenerated charges up to 25 fs is achieved. The highly efficient interband transition, small conduction band energy level difference (less than 100 meV), and exceptionally strong e-p coupling synergistically promote the ultrafast transfer of photo-generated charges. Together with the merits of multilayer 1T'-MoTe2 such as higher carrier densities and lower resistance, these findings open the door to potentially ultra-high performance optoelectronic applications.

Lipid-mediated biosynthetic labeling strategy for in vivo dynamic tracing of avian influenza virus infection.

Monitoring the infection behavior of avian influenza viruses is crucial for understanding viral pathogenesis and preventing its epidemics among people. A number of viral labeling methods have been utilized for tracking viral infection process, but most of them are laborious or decreasing viral activity. Herein we explored a lipid biosynthetic labeling strategy for dynamical tracking the infection of H5N1 pseudotype virus (H5N1p) in host. Biotinylated lipids (biotinyl Cap-PE) were successfully incorporated into viral envelope when it underwent budding process by taking advantage of host cell-derived lipid metabolism. Biotin-H5N1p virus was effectively in situ-labeled with streptavidin-modified near-infrared quantum dots (NIR SA-QDs) using streptavidin-biotin conjugation with well-preserved virus activities. Dual-labeled imaging obviously shows that H5N1p viruses are primarily taken up in host cells via clathrin-mediated endocytosis. In animal models, Virus-conjugated NIR QDs displayed extraordinary photoluminescence, superior stability, and tissue penetration in lung, allowing us to long-term monitor respiratory viral infection in a noninvasive manner. Importantly, the co-localization of viral hemagglutinin protein and QDs in infected lung further conformed the dynamic infection process of virus in vivo. Hence, this in situ QD-labeling strategy based on cell natural biosynthesis provides a brand-new and reliable tool for noninvasion visualizing viral infection in body in a real-time manner.

Quasiparticle Band Structure and Phonon-Induced Band Gap Renormalization of the Lead-Free Halide Double Perovskite Cs2InAgCl6

The lead-free halide double perovskite Cs2InAgCl6 was recently designed in silico and subsequently synthesized in the lab. This perovskite is a wide-gap semiconductor with a direct band gap and exhibits extraordinary photoluminescence in the visible range upon Na doping. The light emission properties of Cs2InAgCl6 have successfully been exploited to fabricate stable single-emitter-based white-light LEDs with near unity quantum efficiency. An intriguing puzzle in the photophysics of this compound is that the onset of optical absorption is around 3 eV, but the luminescence peak is found around 2 eV. As a first step toward elucidating this mismatch and clarifying the atomic-scale mechanisms underpinning the observed luminescence, here, we report a detailed investigation of the quasiparticle band structure of Cs2InAgCl6 as well as the phonon-induced renormalization of the band structure. We perform calculations of bang gaps and effective masses using the GW method, and we calculate the phonon-induced band structure renormalization using the special displacement method. We find that GW calculations are rather sensitive to the functional used in the density functional theory calculations and that self-consistency on the eigenvalues is necessary to achieve quantitative agreement with experiments. Our most accurate band gap at room temperature is in the range of 3.1–3.2 eV and includes a phonon-induced gap renormalization of 0.2 eV. By computing the phonon-induced mass enhancement, we find that the electron carriers are in the weak polaronic coupling regime, while hole carriers are in the intermediate coupling regime as a result of the localized and directional nature of the Ag eg 4d states at the valence band top.

Protein-protected metal nanoclusters: An emerging ultra-small nanozyme.

Protein-protected metal nanoclusters (MNCs), typically consisting of several to a hundred metal atoms with a protein outer layer used for protecting clusters from aggregation, are excellent fluorescent labels for biomedical applications due to their extraordinary photoluminescence, facile synthesis and good biocompatibility. Interestingly, many protein-protected MNCs have also been reported to exhibit intrinsic enzyme-like activities, namely peroxidase, oxidase and catalase activities, and are consequently used for biological analysis and environmental treatment. These findings have extended the horizon of protein-protected MNCs' properties as well as their application in various fields. Furthermore, in the field of nanozymes, protein-protected MNCs have emerged as an outstanding new addition. Due to their ultra-small size (<2 nm), they usually have higher catalytic activity, more suitable size for in vivo application, better biocompatibility and photoluminescence in comparison with large size nanozymes. In this review, we will systematically introduce the significant advances in this field and critically discuss the challenges that lie ahead. Ultra-small nanozymes based on protein-protected MNCs are on the verge of attracting great interest across various disciplines and will stimulate research in the fields of nanotechnology and biology. This article is characterized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Reliable Synthesis of Large‐Area Monolayer WS2 Single Crystals, Films, and Heterostructures with Extraordinary Photoluminescence Induced by Water Intercalation

AbstractTwo‐dimensional transition metal dichalcogenides (TMDs) hold great potential for future low‐energy optoelectronics owing to their unique electronic, optical, and mechanical properties. Chemical vapor deposition (CVD) is the technique widely used for the synthesis of large‐area TMDs. However, due to high sensitivity to the growth environment, reliable synthesis of monolayer TMDs via CVD remains challenging. Here a controllable CVD process is developed for large‐area synthesis of monolayer WS2 crystals, films, and in‐plane graphene–WS2 heterostructures by cleaning the reaction tube with hydrochloric acid, sulfuric acid, and aqua regia. The concise cleaning process can remove the residual contaminates attached to the CVD reaction tube and crucibles, reducing the nucleation density but enhancing the diffusion length of WS2 species. The photoluminescence (PL) mappings of a WS2 single crystal and film reveal that the extraordinary PL around the edges of a triangular single crystal is induced by ambient water intercalation at the WS2–sapphire interface. The extraordinary PL can be controlled by the choice of substrates with different wettabilities.

Origin of extraordinary luminescence shift in graphene quantum dots with varying excitation energy: An experimental evidence of localized sp2 carbon subdomain

We report the extraordinary photoluminescence (PL) behavior of high-quality graphene quantum dots (GQDs) prepared with a graphite intercalation compound method: the alternating PL peak shifts (redshift-blueshift-redshift) with increasing the excitation wavelength. The PL peak position is redshift in the excitation wavelength range 250–270 nm, subsequently blueshift in 270–290 nm, and again redshift in the range 290–330 nm. This unconventional optical response of the GQDs is attributed to two types of energy states: intrinsic states formed by localized sp2 carbon subdomains and extrinsic states created by various oxygen-functional groups. The PL behavior of GQDs shows different tendencies according to the size and amount of oxygen-functional groups. Furthermore, since the extrinsic states of GQDs can be inactivated under acidic condition, its extraordinary PL behavior of high-quality GQDs with varying excitation wavelength largely recedes. On the other hand, we clearly observed these alternating PL shift behaviors when localized sp2 carbon subdomains with intrinsic emission are artificially formed by reducing oxygen-functional groups in graphene oxide quantum dots, which have mostly the extrinsic PL originated from the energy states of various oxygen-functional groups. The results offer experimental evidence for the existence of localized sp2 carbon subdomains and provide key information that clarifies the electronic structure of GQDs and their derivatives.

Extraordinary photoluminescence behavior of an efficient electrochemiluminophore: Tb(III) chelated by 2,6-bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol

The reactivities of lanthanide ions in their excited states are first considered in water and the energy diagrams of most important of them are sketched to illustrate the highly oxidizing and reducing species involved reacting with one-electron steps. Anomalous photoluminescence behavior of Tb(III) chelated by 2,6-bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol is studied. The present chelate is known to show relative strong chemiluminescence in the presence of hydrated electron and oxidizing radicals but it shows an extraordinarily short luminescence lifetime of radiative relaxation of its 5D4 state under photoexcitation.

Magnetic field induced extraordinary photoluminescence enhancement in Er3+:YVO4 single crystal

A bright green photoluminescence (PL) from 4S3∕2 → 4I15∕2 emission band in Er3+:YVO4 single crystal has been observed with the excitation of an argon laser at 488.0 nm. More than two orders of PL enhancement have been obtained under the effect of magnetic fields, and the enhancement factor f reaches 170 when the applied magnetic field is 7.7 T under the sample temperature of 4.2 K. Unusually, the PL enhancements only happen at some certain magnetic fields (Bcs), and a decrease of sample temperature will lead to the increase of f and decrease of Bc. The results confirm that this PL enhancement originates from the resonance excitation of the electron transitions induced by the cross of the laser energy and the absorption energy modulated by both the magnetic field and temperature. This special PL enhancement in Er3+:YVO4 single crystal can be applied in the calibration of pulsed high magnetic field, detection of material fine energy structures, and modulation of magneto-optical devices.

Synthesis of strongly fluorescent molybdenum disulfide nanosheets for cell-targeted labeling.

MoS2 nanosheets with polydispersity of the lateral dimensions from natural mineral molybdenite have been prepared in the emulsions microenvironment built by the water/surfactant/CO2 system. The size, thickness, and atomic structure are characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and laser-scattering particle size analysis. Meanwhile, by the analysis of photoluminescence spectroscopy and microscope, the MoS2 nanosheets with smaller lateral dimensions exhibit extraordinary photoluminescence properties different from those with relatively larger lateral dimensions. The discovery of the excitation dependent photoluminescence for MoS2 nanosheets makes them potentially of interests for the applications in optoelectronics and biology. Moreover, we demonstrate that the fabricated MoS2 nanosheets can be a nontoxic fluorescent label for cell-targeted labeling application.

Extraordinary photoluminescence and strong temperature/angle-dependent Raman responses in few-layer phosphorene.

Phosphorene is a new family member of two-dimensional materials. We observed strong and highly layer-dependent photoluminescence in few-layer phosphorene (two to five layers). The results confirmed the theoretical prediction that few-layer phosphorene has a direct and layer-sensitive band gap. We also demonstrated that few-layer phosphorene is more sensitive to temperature modulation than graphene and MoS2 in Raman scattering. The anisotropic Raman response in few-layer phosphorene has enabled us to use an optical method to quickly determine the crystalline orientation without tunneling electron microscopy or scanning tunneling microscopy. Our results provide much needed experimental information about the band structures and exciton nature in few-layer phosphorene.

Composition-dependent photoluminescence intensity and prolonged recombination lifetime of perovskite CH3NH3PbBr(3-x)Cl(x) films.

Mixed halide perovskites CH3NH3PbBr3-xClx (x = 0.6-1.2) with different compositions of halogens exhibit drastically changed optical properties. In particular, the thin films prepared with these perovskites demonstrate extraordinary photoluminescence emission intensities and prolonged recombination lifetimes up to 446 ns, which are desirable for light emitting and photovoltaic applications.

Extraordinary infrared photoluminescence efficiency of Er0.1Yb1.9SiO5 films on SiO2/Si substrates

Extraordinary infrared photoluminescence efficiency was found for Er2SiO5 film by optimizing the composition of Yb additions on SiO2/Si substrates. Above two orders of magnitude enhanced 1.53 μm Er3+ photoluminescence for the Er0.1Yb1.9SiO5 film on SiO2/Si substrate was obtained by pumping at 980 nm compared with pure Er2SiO5 film on Si substrate at 654 nm. All Er ions for Er0.1Yb1.9SiO5 film are optically active. The decreased nonradiative transient rate leads to extraordinary photoluminescence efficiency in the Er0.1Yb1.9SiO5 film. It indicated that the Er0.1Yb1.9SiO5 film is the sought candidate material for compact waveguide amplifiers and emitters in silicon photonics integration.

Controlled growth of ZnO nanorods by polymer template and their photoluminescence properties

A large amount of one-dimensional ZnO nanorods with diameters in 15–50 nm aligned in radial cluster were successfully synthesized by polar polymer polyvinyl alcohol (PVA) as soft-template. The growth of ZnO nanorods was controlled by changing annealing temperature. The evolution of the morphology and microstructure was investigated by scanning electron microscope, transmission electron microscope and X-ray diffraction. It is shown that ZnO nanorods tend to be uniform and the crystallization is gradually improved with the temperature increasing from 400° to 700°. The photoluminescence spectra of products show a strong ultra violet emission and relatively weak defect emissions. The sharp strong emission peak at 354 nm owing to the inter-band transition indicates the extraordinary photoluminescence property of ZnO nanorods.

Photoluminescence of GaAs layers hybrid-grown on Si by MBE and LPE

We have found extraordinary photoluminescence (PL) for GaAs layers grown on Si substrates by the MBE-LPE hybrid method, which is molecular beam epitaxy (MBE) combined with subsequent liquid phase epitaxy (LPE). The PL spectra showed only one broad peak with a large red-shift (44–98 meV) and large intensity compared with the exciton peak of an MBE-grown sample. The red-shift increased with raising the growth temperature of LPE for the hybrid growth. Si impurities unintentionally incorporated into the MBE-grown region as well as the LPE-grown region of the hybrid-grown GaAs layers were observed by SIMS measurements. The PL peaks with large red-shift of the hybrid-grown layers were considered to arise from a formation of additional energy levels in the band structure due to the compensated Si impurities in the LPE-grown region.