Phosphorene Quantum Dots Research Articles

Induced magnetic effects on intrinsic properties of edge-passivated triangular zigzag phosphorene quantum dots using spin-polarized density functional theory

The electrical and magnetic characteristics of edge-passivated triangular zigzag phosphorene quantum dots, saturated with hydrogen and oxygen atoms, have been investigated using spin-polarized density functional theory. The findings indicate that oxygen passivation alters the bond lengths, cohesive energies, and bandgaps of the quantum dots, leading to increased stability and magnetism due to unbonded single electrons in the oxygen atoms. The study also explored the impact of an external electric field on the energy gap, molecular orbital distribution, and local spin density of selected quantum dots. Our results show significant changes in the energy spectra and magnetic moments of the magnetized structures. The tunability of the magnetic and electronic attributes of triangular phosphorene quantum dots can be exploited in designing electronic and spintronic devices.

Light‐Guided Genetic Scissors Based on Phosphorene Quantum Dot

AbstractGenetic engineering faces persistent challenges in achieving precise Deoxyribonucleic acid (DNA) cleavage, especially with the limitations associated with current enzyme‐based methods, exemplified by issues in CRISPR technologies. This study introduces a groundbreaking approach: utilizing reactive oxygen species (ROS) generated by Multiphoton Absorption (MPA)‐excited Black Phosphorus Quantum Dots (BPQDs) under femto‐second laser irradiation. This innovative method not only allows excitation with lower energy but also enhances overall efficiency. The integration of complementary RNA sequences facilitates high‐efficiency, site‐selective DNA cleavage in the system, named “TADPOLE” (Targeted DNA Precision Oriented Laser Excision). Beyond its precision in targeting arbitrary DNA sequences using quantum dots, TADPOLE harnesses the unique multiphoton absorption property of BPQDs, enabling excitation with lower‐energy light sources suitable for in vivo applications in the future. Moreover, the approach integrates guiding RNA and ultrafast laser technology to provide precise control over local ROS generation and minimal heat production. This guarantees site‐specific DNA cleavage while mitigating the risk of damage to non‐targeted sequences. In summary, this study catalyzes advancements in enzyme‐free DNA cleavage technologies, with transformative implications for genetic engineering, biotechnology, and medicine. The holistic precision, versatility, and endurance presented by TADPOLE open new avenues for targeted gene therapies and transformative applications in related fields.

Temperature-dependent charge carrier behavior in phosphorene quantum dots probed by terahertz time-domain spectroscopy.

Although phosphorene quantum dots (PQDs) have gained significant attention in optoelectronics and physics due to their unique optical responses, the low-frequency electromagnetic properties of PQDs and the effects of temperature still remain largely unexplored. Herein, we investigate the temperature-dependent terahertz (THz) response of PQDs by using THz time-domain spectroscopy. Effective THz conductivity of the PQD sample is extracted based on THz measurements to analyze the charge carrier behavior. It is shown that the carriers in the PQDs can be approximated as a weakly confined Drude gas of classical and noninteracting charge particles, which are described by the modified Drude-Smith formula. Then, we also obtain the temperature dependences of the effective characteristic parameters for the charge carriers. As the temperature increases, the plasma frequency linearly enhances whereas both of the carrier diffusion time and the momentum scattering time decrease, which are akin to conventional semiconductors to a large extent. In addition, the confinement factor is closed to 1 and nearly insensitive to temperature. These results are helpful to gain an in-depth understanding of the low-frequency electromagnetic response of charge carriers in PQDs and to explore new applications in photonics and optoelectronics.

Synthesis of Black Phosphorene Quantum Dots from Red Phosphorus.

Black phosphorene quantum dots (BPQDs) are most commonly derived from high-cost black phosphorus, while previous syntheses from the low-cost red phosphorus (Pred ) allotrope are highly oxidised. Herein, we present an intrinsically scalable method to produce high quality BPQDs, by first ball-milling Pred to create nanocrystalline Pblack and subsequent reductive etching using lithium electride solvated in liquid ammonia. The resultant ~25 nm BPQDs are crystalline with low oxygen content, and spontaneously soluble as individualized monolayers in tertiary amide solvents, as directly imaged by liquid-phase transmission electron microscopy. This new method presents a scalable route to producing quantities of high quality BPQDs for academic and industrial applications.

Electrochemical Biosensor Based on Horseradish Peroxidase and Black Phosphorene Quantum Dot Modified Electrode.

Black phosphorene quantum dots (BPQDs) were prepared by ultrasonic-assisted liquid-phase exfoliation and centrifugation with morphologies proved by TEM results. Furthermore, an electrochemical enzyme sensor was prepared by co-modification of BPQDs with horseradish peroxidase (HRP) on the surface of a carbon ionic liquid electrode (CILE) for the first time. The direct electrochemical behavior of HRP was studied with a pair of well-shaped voltammetric peaks that appeared, indicating that the existence of BPQDs was beneficial to accelerate the electron transfer rate between HRP and the electrode surface. This was due to the excellent properties of BPQDs, such as small particle size, high interfacial reaction activity, fast conductivity, and good biocompatibility. The presence of BPQDs on the electrode surface provided a fast channel for direct electron transfer of HRP. Therefore, the constructed electrochemical HRP biosensor was firstly used to investigate the electrocatalytic behavior of trichloroacetic acid (TCA) and potassium bromate (KBrO3), and the wide linear detection ranges of TCA and KBrO3 were 4.0-600.0 mmol/L and 2.0-57.0 mmol/L, respectively. The modified electrode was applied to the actual samples detection with satisfactory results.

Anisotropic Behavior of Optical Properties in Edge-Modified Phosphorene Quantum Dots

The evolution of optical properties in low-dimensional phosphorene quantum dots remains a largely unexplored area, with great potential for applications as optoelectronic devices. Herein, we present a comprehensive analysis of the optical properties of edge-passivated (H, NH2, Cl, OCN, CN) monolayer phosphorene quantum dots using density functional theory and time-dependent density functional theory calculations. An extensive characterization of absorptions, nonradiative relaxations, radiative emissions, radiative lifetimes, and the high-frequency Raman modes (Ag1, B2g, and Ag2) is undertaken, emphasizing the role of material directionality, quantum confinement, and edge passivation on the evolution of these properties. Our results indicate that optical absorptions and emissions are preferred from the armchair direction of phosphorene regardless of the type of edge functionalization or system size, rendering these systems as potential natural linear optical polarizers in the UV–vis region. Larger phosphorene quantum dots have smaller Stokes shifts and less geometric variation upon relaxation, leading to decreased radiative lifetimes. Additionally, we identify an uncharacteristic Raman response associated with dissimilar shifting trends of the Ag peaks that arise from the planar growth of phosphorene quantum dots in the armchair or the zigzag direction. The behavior is attributed to the competing effects of mass coupling and improved bond strength.

Reduced Phosphorene Quantum Dot Incorporated Flexible Bio-Electronic Device for the Detection of Uric Acid in Real Media

Among all developed 2D materials, phosphorene is in notable demand in recent times due to its distinctive electrical performance in biomedical applications. Zero-dimensional phosphorene quantum dot semiconducting material is a promising candidate that initiated a platform for fabricating high-performance electrical biosensors. In this study, we have successfully developed the material reduced phosphorene quantum dots (rPhQDs) of an average size of 2.1–2.3 nm using a simple hydrothermal technique. This material can be utilized as an electrical bio-sensing platform to detect uric acid in aqueous media as well as in real samples such as human blood serum and artificial urine. Biodegradable polymer composites of rPhQDs show unique current–voltage properties. They can be used to fabricate electrical devices that selectively detect uric acid in human blood serum and urine samples in the linear range of 1–5 μM. The corresponding detection limits for aqueous media, human blood serum, and artificial urine are 0.809, 0.5292, and 1.065 μM, respectively. We have investigated the driving force responsible for this selective electrical sensing and found that improvement of ionic movement in the presence of analytes plays a prominent role that can be established by measuring the transport number of the nano-bio-composite film. The device has the potential for successful detection of uric acid quantities in human blood serum and artificial urine.

Point-defect engineering on phosphorene quantum dots for DNA bases adsorption and sensor performance

We have performed density functional theory (DFT) calculations to understand the interaction of DNA bases with pristine and point-defective black phosphorus quantum dots (BPQDs). The point-defect BPQDs show improved affinity for guanine molecule, and therefore are beneficial for guanine adsorption. More interestingly, the point defects in BPQDs can enhance the sensitivity to some extent for guanine, because the significant energy gap changes have occurred after the adsorption. The orbital hybridization near the Fermi energy level leads to significant energy gap changes in the point-defect BPQDs. Electron density topological analyses indicate that the electrostatic interactions play an important role in the stabilizing between base molecules and substrates. • DNA bases can be adsorbed on SV and DV BPQDs through physisorption state. • The electronic structures of SV and DV BPQDs are significantly altered upon guanine adsorption. • The electrostatic interactions were revealed by QTAIM and IGM. • The orbital interaction between guanine and defect BPQDs is significant.

Wigner molecules in phosphorene quantum dots

We study Wigner crystallization of electron systems in phosphorene quantum dots with confinement of an electrostatic origin with both circular and elongated geometry. The anisotropy of the effective mass allows for the formation of Wigner molecules in the laboratory frame with a confined charge density that has lower symmetry than the confinement potential. We find that in circular quantum dots separate single-electron islands are formed for two and four confined electrons but not for three trapped carriers. The spectral signatures of the Wigner crystallization to be resolved by transport spectroscopy are discussed. Systems with Wigner molecule states are characterized by a nearly degenerate ground state at $B=0$ and are easily spin-polarized by the external magnetic field. In electron systems for which the single-electron islands are not formed, a more even distribution of excited states at $B=0$ is observed, and the confined system undergoes ground state symmetry transitions at magnetic fields of the order of 1 Tesla. The system of five electrons in a circular quantum dot is indicated as a special case with two charge configurations that appear in the ground-state as the magnetic field is changed: one with the single electron islands formed in the laboratory frame and the other where only the pair-correlation function in the inner coordinates of the system has a molecular form as for three electrons. The formation of Wigner molecules of quasi-1D form is easier for the orientation of elongated quantum dots along the zigzag direction with heavier electron mass. The smaller electron effective mass along the armchair direction allows for freezing out the transverse degree of freedom in the electron motion.

Electronic properties and optical absorption of multi-layer phosphorene quantum rings

This paper presents the study of the electronic and optical properties of multi-layer phosphorene quantum rings (PQRs) by using the tight-binding model. The effects of the hole size and position, along with the number of layers in the PQR on the energy levels and the optical spectrum, are numerically analyzed. The calculations show that the electronic and optical properties can be tuned by the hole size, the hole position, and the number of layers. The coupling of the inner and outer edges depends strongly on the position of the hole. The findings suggest that the layer-dependent optical properties of phosphorene quantum dots and PQRs are related to the parity of the number of layers.

Quantum confinement and effective masses dependence in black phosphorus quantum dots and phosphorene

In the present study, quantum confinement effect in phosphorene and black phosphorus quantum dots is extensively studied from experimental and theoretical viewpoints. These quantum structures were prepared with the help of Benzonitrile solvent using Liquid Phase Exfoliation and solvothermal-assisted Liquid Phase Exfoliation, respectively. On one hand, Fourier-transform infrared spectroscopy shows no sign of phosphorus oxidation in both phosphorene and black phosphorus quantum dots solutions. Furthermore, Raman spectroscopy showed a shift in B2gandAg2 phonon modes for phosphorene and black phosphorus quantum dots as compared to bulk black phosphorus. On the other hand, structural characterization via high-resolution transmission electron microscopy imaging and electron diffraction patterns showed a high degree of crystallinity in both quantum structures with no sign of aggregations. Optical properties characterization showed the expected increase in the bandgap value for both quantum structures, which were supported by theoretical calculations using density functional theory and effective mass approximation. Interestingly, we demonstrate that the quantum confinement observed in phosphorene is weakened to the expected extent, relative to that in BPQDs, by the loss of two confinement dimensions. Appropriate models, describing the bandgap and effective mass dependence as a function of the confinement regime, are presented.

Phosphorene quantum dots: synthesis, properties and catalytic applications.

Phosphorene quantum dots (PQDs) belong to a new class of zero-dimensional functional nanostructures with unique physicochemical and surface properties in comparison with few-layer phosphorene and other 2D analogues. Tunable band gap as a function of number of layers, ease of passivation and high carrier mobility of PQDs have attracted considerable attention in catalysis research due to which spectacular progress has been made in PQD research over the last few years. PQDs are now considered as promising catalytic materials for electrocatalytic water splitting and nitrogen reduction, lithium-sulfur batteries, solar light-driven energy devices and biocatalysis, either in pristine form or as an active component for constructing heterostructures with other 2D materials. In the light of these recent advances, it is worthwhile to review and consolidate PQD research in catalytic applications to understand the challenges ahead and suggest possible solutions. In this review, we systematically summarize various synthetic strategies including ultrasonic and electrochemical exfoliation, solvothermal treatment, blender breaking, milling, crushing and pulsed laser irradiation. Furthermore, the physiochemical properties of PQDs are discussed based on both experimental and theoretical perspectives. The potential applications of PQDs in catalysis with special emphasis on photocatalysis (solar light-driven energy devices) and electrocatalysis (oxygen evolution reactions and hydrogen evolution reactions) -are critically discussed along with the present status, challenges and future perspectives.

Optoelectronic properties of blue phosphorene quantum dots: A first principles study

In this research, we used first principles methods with density functional theory (DFT) to evaluate simultaneously the electronic and optical properties of defect-free and single-vacancy blue phosphorene quantum dots. We used the generalized gradient approximation of the Perdew-Burke-Ernzerhof (PBE) functional as exchange-correlation functional. We have shown that the band gaps of these quantum dots can be varies in between 2.56 eV and 2.80 eV and the band gap decreases with increasing the system sizes. In the presence of single vacancy, the band gap significantly shrinks resulting from the shift of the conduction band towards the valence band. We also observed additional polaron states close to the Fermi level, indicating the existence of dangling bonds being established by the unbalanced charge Phosphorous atoms surrounding the defect sites. The absorption coefficent increased noticably in the visible light range. The appearance of the polaron states resulted in newly formed absorption peaks in the visible light range. Our results showed the clear effect of defect on light conversion efficiency of solar panels embedding blue phosphorene quantum dots.

Point-Defect Engineering on Phosphorene Quantum Dots for DNA Bases Adsorption and Sensor Performance

Point-Defect Engineering on Phosphorene Quantum Dots for DNA Bases Adsorption and Sensor Performance

Edge effects on the intrinsic magnetism in ferromagnetic triangular phosphorene quantum dots using fully spin-polarized calculations

This project involves discovering the electronic and magnetic properties of nanometer-sized phosphorene structures with triangular shapes in both zigzag and armchair termination types. The goal is to discuss the relationship between the electronic states belonging to the different conditions of these phosphorene quantum dots and their intrinsic magnetic properties. For this purpose, we consider electronic interactions utilizing the spin-polarized density functional theory calculations, and then the results compare with the data generated from tight-binding calculations. Both descriptions yield mid-gap states in the spectrum of ferromagnetic structures. Our results in non-spin computations without any geometry optimization were matched by tight-binding calculations which shows that the tight-binding method is an inefficient approximation in analyzing the optimized spin samples. Unlike graphene, in our spin-polarized calculations, we have obtained empty mid-gap states in the spectrum of ferromagnetic triangular phosphorene quantum dots. The edge atoms of these structures are known as the magnetic atoms with an unequal contribution of spin up and spin down. To prevent deforming the initial structures, the dangling bonds at the edge atoms were passivated in two types, fully hydrogenated and partial passivation with oxygen atoms. Oxygen doping was required for introducing magnetism to the non-spin edges of the fully hydrogenated case.

Negative quasiparticle shifts in phosphorene quantum dots

It is commonly believed that electron correlations would open up a quasiparticle gap in semiconductors. Contrary to this intuitive expectation, here we reveal that phosphorene quantum dots (PQDs) may exhibit just the opposite effect. By using a configuration interaction approach beyond the conventional double-excitation scheme, quasiparticle energies are calculated for hexagonal and rectangular PQDs in various dielectric environments. For the hexagonal PQD with a nominal gap of 2.26 eV, it is found that the quasiparticle shift decreases by more than 500 meV and eventually becomes negative when the effective dielectric constant is reduced from 20.0 to 5.0. For other trapezoidal, triangular, and rectangular PQDs, the quasiparticle shift exhibits a similar amount of decrement after the same change in the dielectric environment. Furthermore, the calculation by adopting the Rytova-Keldysh potential, which may be more suitable to describe two-dimensional screening, also shows a very similar result, although with smaller decrement of the quasiparticle shift. The origin of this anomalous quasiparticle shift is believed to be related to the long-range electron-electron interactions in the distinctive lattice structure of PQDs, as a similar phenomenon has never been found in graphene quantum dots.

Magneto-optical properties of bilayer phosphorene quantum dots.

Using the tight-binding approach, we investigate the electronic and magneto-optical properties of bilayer phosphorene quantum dots (BLPQDs) in the presence of perpendicular electric and magnetic fields. The magneto-energy spectra of the BLPQDs exhibit Aharonov-Bohm oscillations. The period and the amplitude of the oscillation decrease with the size of the BLPQDs. An oscillatory behavior of the local density of states (LDOS) versus the magnetic field is observed, as well as the appearance of the spatial Aharonov-Bohm oscillations in the LDOS. In the absence of the electric field, there exists an s-fold degeneracy (s absolutely flat bands at exactly zero energy) arising from the edge-mode states, where s is the smaller value between M and N, where M and N are the number of phosphorus atoms along the x and y axis, respectively, in a rectangular BLBPQD. The absorption spectra of the BLPQDs are obtained for both in-plane and out-of-plane polarizations. Compared with the absorption spectra of graphene dots, the absorption of an out-of-plane polarization of the incident light is high compared to that of in-plane polarizations. On the other hand, the absorption spectra due to in-plane polarizations are almost the same in the case of graphene, whereas they are considerably different in BLBPQDs. Importantly, the appearance of several sharp and high absorption peaks in the near-infrared (NIR) range dictates the BLBPQDs for application and development of bioimaging, biomedicine and drug delivery technology. More importantly, both the location and intensity of these NIR peaks depend characteristically on the orientation of the polarization of the incident light, which can be desirably tuned by the simultaneous engineering of magnetic and electric fields. Such unique advantage of the anisotropic optical feature enables a new degree of freedom for achieving novel polarization-dependent photonic devices. The dual magnetic and electric field tunable optical and electrical features of the BLPQDs are expected to have important consequences for the development of multifunctional magneto-optoelectronic devices and provide insight into the applicability of quantum photopic technologies based on BLBPQDs.

Electronic and optical properties of the edge states in phosphorene quantum rings

We theoretically investigate the electronic and optical properties of the rectangular phosphorene quantum rings (RPQRs) including the coulomb interaction using the Hubbard method. Our calculations show that the energy levels can be adjusted by changing the outer and inner ring width of the RPQRs. Newly edge states appear along the inner boundary of the RPQRs within the formal bandgap of a counterpart rectangular phosphorene quantum dots (RPQDs) without the inner hole. The edge states shows distinct responding to the size of the inner hole and the external field as compared to the bulk states. There is dark-to-bright transition in the optical adsorption spectrum of RPQRs tuned by the external field which is quite different from that in the RPQDs. This feature offers us a practical way to modulate the electronic and optical properties in phosphorene QDs and rings.

A DFT Study of Optoelectronic Properties and Electronic Structure of Edge-Modified Phosphorene Quantum Dots Interacting with Polyaniline

A DFT Study of Optoelectronic Properties and Electronic Structure of Edge-Modified Phosphorene Quantum Dots Interacting with Polyaniline

Abnormal scaling of excitons in phosphorene quantum dots.

Excitonic states of a many-electron system in phosphorene quantum dots (PQDs) are investigated theoretically by using a configuration interaction approach. For a triangular PQD in various dielectric environments, its exciton is found to obey two distinct scaling rules. When there is a strong screening effect present in the nanodot, the exciton binding energy (Δex) is shown to be around -150 meV as the long-range Coulomb interactions are totally suppressed and it increases to about 100 meV when the effective dielectric constant (εr) decreases to 12.5. Over this range of εr, Δex is found to be well fitted into a quadratic form of εr-1, which scales neither linearly with εr-2 like the case of bulk three-dimensional semiconductors nor linearly with εr-1 like the case previously reported for graphene nanostructures. When εr is reduced below 10.0, however, Δex is shown to exhibit a perfect linear relationship with εr-1, which behaves just like that of a two-dimensional graphene sheet. On the other hand, with the reduced εr, the quasiparticle gap is found to decrease instead of increasing like in most of the semiconductor nanostructures. As a result, it is revealed that the relationship of Δex with the quasi-particle gap deviates largely from the linear one previously reported for graphene and many other two-dimensional materials.