Using density functional theory coupled to the Boltzmann transport equation with relaxation time approximation, we study the electronic structure and carrier mobility of graphene-like hexagonal boron phosphide (h-BP) monolayer and H-terminated armchair boron phosphide nanoribbons (ABPNRs). Our results show that the carrier mobility can reach over 10 4 cm 2 V −1 s −1 for electron and 5 × 10 3 cm 2 V −1 s −1 for hole in monolayer sheet. The carrier mobility in the ABPNRs is in the range of 10 3 to 10 4 cm 2 V −1 s −1 , and we find that the width of nanoribbon plays an important role in tuning the polarity of the carrier transport, which exhibits a distinct 3p (p is a positive integer) alternating behavior. The staggering oscillating behavior of mobility should be attributed to different bond characteristics of the edge states in the ABPNRs. Moreover, the Hterminated zigzag boron phosphide nanoribbons (ZBPNRs) have the characteristics of p-type semiconductors in electrical conduction, and the carrier mobility is increased with the width of the nanoribbons and no alternating size-dependent carrier polarity is found. The high carrier mobility and adjustable polarity of transport suggest that h-BP is a promising candidate material for application in future nanoelectronic devices.

Understanding the photoexcited carrier-relaxation actions in ultrasmall black phosphorus quantum dots (BPQDs) will play a crucial role in the fields of electronics and optoelectronics. Herein, we report the ultraviolet (UV) saturable absorption and ultrafast photoexcited carrier-relaxation dynamics of BPQDs. The ultrasmall BPQDs are synthesized using a facile liquid-exfoliation method and possess a diameter of 3.8 ± 0.6 nm and a thickness of 1.5 ± 0.4 nm. Femtosecond open-aperture (OA) Z-scan measurements showed typical saturable absorption properties in the UV band. A negative nonlinear optical (NLO) absorption coefficient of -(1.4 ± 0.3) × 10 cm GW and a saturable intensity of 6.6 ± 1.3 GW cm were determined. Using a degenerate pump-probe technique, an ultrafast photoexcited carrier-recombination time was observed in the range of 216-305 fs, which was 3 orders of magnitude faster than that of BP nanosheets. Such an ultrafast relaxation component may be attributable to the edge- and step-mediated recombination and was confirmed by our density functional theory (DFT) calculations. This work provides fundamental insight into the underlying mechanism of the photoexcited carrier relaxation dynamic action in BPQDs which can enable UV photonic devices.

Using density functional theory coupled with the Boltzmann transport equation with relaxation time approximation, we have studied the strain effect on the electronic structure and carrier mobility of two-dimensional monolayer GeP 3 . We find that the energies of valence band maximum and conduction band minimum are nearly linearly shifted with a biaxial strain in the range of −4% to 6%, and the band structure experiences a remarkable transition from semiconductor to metal with the appropriate compression (−5% strain). Under biaxial strain, the mobility of the electron and hole in monolayer GeP 3 reduces and increases by more than one order of magnitude, respectively. It is suggested that it is possible to perform successive transitions from an n-type semiconductor (−4% strain) to a good performance p-semiconductor (+6% strain) by applying strain in monolayer GeP 3 , which is potentially useful for flexible electronics and nanosized mechanical sensors.

0-Dimensional (0D) CsPbBr3 QDs were integrated with 2D bismuthene to obtain a 0D/2D nanohybrid with tunable charge transfer efficiency.

Biodegradability is one of the most critical issues for silica-based nanodrug delivery systems because they are crucial prerequisites for the successful translation in clinics. In this work, a novel mesoporous silica-calcium phosphate (MS-CAP) hybrid nanocarrier with a fast pH-responsive biodegradation rate was developed by a one-step method, where CAP precursors (Ca and PO) were incorporated into silica matrix during the growth process. The morphology and structure of MS-CAP were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N adsorption-desorption isotherms, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, the drug loading and the release behavior of MS-CAP have been tested. TEM and inductively coupled plasma-optical emission spectrometry results indicated that the pH-responsive biodegradation of MS-CAP was so fast that could be almost finished within 24 h owing to the easy dissolution of CAP embedded in the particle and the escape of Ca from the structure of Si-O-Ca in acid environment. The MS-CAP exhibited a high doxorubicin (DOX) entrapment efficiency (EE) of 97.79%, which was about fourfold higher compared with that of pure mesoporous silica nanoparticles, and our density functional theory calculational results suggested that the higher drug EE of MS-CAP would originate from the strong interaction between calcium in the particle and carboxylate group of DOX. The loaded DOX was effectively released, with a cumulative release as high as 98.06% within 48 h at pH 4.5 in buffer solution, owing to the rapid degradation of MS-CAP. The obtained results indicated that the as-synthesized MS-CAP could act as a promising drug delivery system and would have a hopeful prospect in the clinical translation.

Two-dimensional monolayer Tellurium, termed as Tellurene (Te), has recently been fabricated in the experiment. In this work, under uniaxial strain applied along either the armchair or zigzag direction with strain strength varying from 0 to 40%, we have investigated the mechanical property of Te including three allotropes (α-Te, β-Te, and γ-Te). Our results show that the β-Te exhibits the most obvious anisotropy in the stress-strain curve, Young's modulus, and Poisson's ratio, which is thought to originate from its inherent structure characteristic. The stress-strain curve demonstrates that the β-Te can withstand relatively high critical strain up to 36% in the armchair direction and 35% in the zigzag direction. The calculated Young's modulus E(θ) of the β-Te is 55 GPa in the zigzag direction and that is 27 GPa in the armchair direction. The comparative high critical strain and small Young's modulus mean that β-Te has good flexibility. Moreover, under the strain range within 15%, the direction being easy to be stretched has a reversion, which is thought to be decided by the competition between the puckered structure and the transfer charge resistant to deformation. Furthermore, when the strain is applied along the direction parallel to the pucker of β-Te, it is interesting to find that Poisson's ratio is negative in the out-of-plane direction. The hinged structure of the β-Te contributes to the negative Poisson's ratio, which can be comprehended by the hypothetical step-by-step evolution process.

Molybdenum disulfide (MoS2) is one of candidate materials for nanoelectronics and optoelectronics devices in future. The electronic and magnetic properties of MoS2 can be regulated by interlayer interaction and vacancy effect. Nevertheless, the combined effect of these two factors on MoS2 is not clearly understood. In this study, we have investigated the impact of single S vacancy combined with interlayer interaction on the properties of bilayer MoS2. Our calculated results show that S vacancy brings impurity states in the band structure of bilayer MoS2, and the energy level of the impurity states can be affected by interlayer distance, which finally disappears in bulk state when the layer distance is relatively small. Moreover, during the compressing of bilayer MoS2, the bottom layer, where S vacancy stays, gets additional charge due to interlayer charge transfer, which first increases, and then decreases due to gradually forming the interlayer S-S covalent bond, as interlayer distance decreases. The change of the additional charge is consistent with the change of the total magnetic moment of bottom layers, no magnetic moment has been found in top layer. The distribution of magnetic moment mainly concentrates on the three Mo atoms around S vacancy, each of whose magnetic moment is very much related to the Mo-Mo length. Our conclusion is that the interlayer charge transfer and S vacancy codetermine the magnetic properties of this system, which maybe a useful way to regulate the electronic and magnetic properties of MoS2 for potential applications.

Two-dimension (2D) materials have attracted interests due to their potential applications in the next generation of nanoelectronics. By using the first-principles calculations based on the density functional theory (DFT), we first investigated the strain induced band structures of hexagonal boron phosphide/blue phosphorus(h-BP/BlueP) heterostructure. The stacking configurations induced electronic structures, and the mechanical flexibility of h-BP/BlueP heterostructure was studied systematically. Their negative formation energy and binding energy as well as excellent lattice match guarantee structural stability. The calculated band structure shows that largest band gap is AB stacking pattern with a direct band gap of 1.07 eV. Additionally, the AB pattern is the most stable one. The biggest band gap can be observed (such as δ = 3%). Compared with stretch, the energy gap is more sensitive under compression. The ultimate strains of h-BP/BlueP heterostructure are 14% in the AB pattern. Furthermore, the different strains of h-BP/BlueP heterostructure have been studied; we found that the band gap and band edges can be modulated by strain, and the negative Poisson's ratio behavior can be observed.