Tunable Charges Research Articles

Chiral Second-Harmonic Generation from Monolayer WS2/Aluminum Plasmonic Vortex Metalens.

Two-dimensional spiral plasmonic structures have emerged as a versatile approach to generate near-field vortex fields with tunable topological charges. We demonstrate here a far-field approach to observe the chiral second-harmonic generation (SHG) at designated visible wavelengths from a single plasmonic vortex metalens. This metalens comprises an Archimedean spiral slit fabricated on atomically flat aluminum epitaxial film, which allows for precise tuning of plasmonic resonances and subsequent transfer of two-dimensional materials on top of the spiral slit. The nonlinear optical measurements show a giant SHG circular dichroism. Furthermore, we have achieved an enhanced chiral SHG conversion efficiency (about an order of magnitude greater than the bare aluminum lens) from monolayer tungsten disulfide (WS2)/aluminum metalens, which is designed at the C-exciton resonance of WS2. Since the C-exciton is not a valley exciton, the enhanced chiral SHG in this hybrid system originates from the plasmonic vortex field-enhanced SHG under the optical spin-orbit interaction.

Structure-based design of charge-conversional drug self-delivery systems for better targeted cancer therapy

Various design and fabrication strategies of carrier-based drug delivery systems have been quickly established and applied for cancer therapy in recent years. These systems contribute greatly to current cancer treatments but further development needs to be made to eliminate obstacles such as low drug loading capacity and severe side effects. To achieve better drug delivery, we propose an innovative strategy for the construction of easy manufactured drug self-delivery systems based on molecular structures, which can be used for the co-delivery of curcuminoids and all the nitrogen-containing derivatives of camptothecin for better targeted cancer therapy with minimized side effects. The formation mechanism investigation demonstrates that the rigid planar structures of camptothecin derivatives and curcuminoids with relevant leaving hydrogens make it possible for them to be assembled into nanoparticles under suitable conditions. These nanoparticles show stabilized particle sizes (100 nm) under various conditions and tunable surface charges which increase from around −10 mV in a normal physiological condition (pH 7.4) to +40 mV under acidic tumor environments. In addition, in vivo mice experiments have demonstrated that, compared to irinotecan (a derivative of camptothecin) itself, the co-delivered irinotecan curcumin nanoparticles exhibited significantly enhanced lung and gallbladder targeting, improved macrophage-clearance escape and ameliorated colorectal cancer treatment with an eradication of life-threatening diarrhea, bringing hope for better targeted chemotherapy and clinical translation. Lastly, the strategy of structure based design of drug self-delivery systems may inspire more research and discoveries of similar self-delivered nano systems for wider pharmaceutical applications.

High-order cylindrical vector beams with tunable topological charge up to 14 directly generated from a microchip laser with high beam quality and high efficiency

Large topological charge optical vortex beams carrying orbital angular momentum have potential applications on optical trapping, optical communication with high capacity, quantum information processing. However, the beam quality is degraded in vortex beams generated with spiral phase plates or resonator mirrors with defect spots and optical conversion efficiency in solid-state lasers is sacrificed by controlling the loss of resonator. It is a big challenge for generating high beam quality, high-order cylindrical vector beams with large topological charge in compact solid-state lasers. Here, high-order cylindrical vector beams [Laguerre-Gaussian (LG) modes with zero degree and order of l, LG0,l] with tunable topological charges up to 14 have been generated in an annular beam pumped Yb:YAG microchip laser by manipulating the pump power-dependent population inversion distribution. Efficient performance with optical efficiency of 17.5% has been achieved. The output power is 1.36 W for a vector-vortex laser with 14 topological charges. The pump power dependent wavelength tunable and dual-wavelength laser oscillation in vector-vortex beams has been observed by controlling the reabsorption loss at 1030 nm. Wavelength tunable, dual-wavelength (1030 and 1050 nm) laser oscillation has been achieved for vector-vortex beams with topological charges of 8, 9, and 10. The laser beam quality factor M2 close to the theoretical value (l + 1) has been achieved for LG0,l vector-vortex beams with tunable topological charges up to 14. This work provides a new effective method for generating large topological charge high-order cylindrical vector beams in solid-state microchip lasers with high efficiency and high beam quality.

Construction of an electroneutral zinc incorporated polymer network nanocomposite membrane with enhanced selectivity for salt/dye separation

Electroneutral nanofiltration (NF) membranes are crucial to the treatment of textile wastewaters with high salinity, but it is challenging to generate electroneutral thin-film composite (TFC) membranes in a broad pH range. In this paper, we demonstrate the fabrication of an electroneutral NF composite membrane with the selective layer comprising of a zinc cation-integrated cross-linked polyvinyl alcohol (PVA)-polyethyleneimine (PEI) polymer network, which was deposited on an interlayer membrane of polydopamine-wrapped carbon nanotubes. The highly ionizable coordinative bonds formed between the Zn(II) ionic species and the amino groups in PEI facilitated ionization to generate hydrophilic and nearly electroneutral membranes with tenable electroneutrality over a broad pH range of 5.0–8.6. Subsequently, the membrane afforded excellent rejection (>99.7%) of bromothymol blue, congo red and direct yellow dye molecules while the low salt retentions of 3.35% (NaCl) and 11.57% (Na2SO4) were realized with moderately high water flux of up to 84 L m−2 h−1 at 5 bar. Further prolonged filtration of a salt/dye mixed feed system demonstrated that the salt presence did not affect the dye separation efficiency leading to the attainment of an unprecedented high NaCl/Congo red selectivity of 932. This highlighted the potentiality of the presented approach for designing membranes with tunable surface charges for the purification of saline textile wastewaters.

Focus shaping of partially coherent radially polarized vortex beam with tunable topological charge

In this paper, we have introduced a new class of partially coherent vector vortex beams, named radially polarized multi-Gaussian Schell-model (MGSM) vortex beam, carrying the vortex phase with tunable topological charges (i.e., both integral and fractional values) as a natural extension of the radially polarized MGSM beam. The tight focusing properties of the radially polarized MGSM vortex beam passing through a high numerical aperture (NA) objective lens are investigated numerically based on the vectorial diffraction theory. Numerical results show that the focal intensity distributions of the radially polarized MGSM vortex beam can be shaped by regulating the structure of the correlation functions and the topological charge of vortex phase. In contrast with the integral vortex beam, the most intriguing property of the fractional vortex beam is that the focal intensity distribution at the focal plane can be nonuniformity and asymmetry, while such unique characteristics will vanish when the spatial coherence length is sufficiently small. Furthermore, some focal fields with novel structure, such as a focal spot with nonuniform asymmetric or an anomalous asymmetric hollow focal field, can be formed by choosing suitable fractional values of topological charge and spatial coherence length. Our results will be useful for optical trapping, especially for trapping of irregular particles or manipulation of absorbing particles.

In-Vitro Study of Cancer Cell Binding and Photothermal Inhibition Efficiency by Gold Nanoparticles-Capped Iron Oxide Nanospheres

Different from the traditional cancer cell targeting through protein biomarkers, strong negative surface charges of cancer cells over normal cells derived from the dramatic excretion of lactate acid by cancer cells due to their glycolysis have been testified as an effective cancer cell binding strategy. In our previous work, polyethylenimine (PEI)-functionalized iron oxide nanoparticles (NPs) with strong positive surface charge and good photothermal property have been applied to kill cancer cells in vitro. Considering the obvious cytotoxicity of the first generation of positively charged nanotherapeutics, second generation of magnetic nanotherapeutics with tunable surface charges was designed and prepared by shield of positively charged surface areas by negatively charged gold nanoparticles (AU NPs). In addition to reducing the cytotoxicity of original NPs, the photothermal property of magnetic NP core was simultaneously enhanced. Herein, the correlation of the capping degree of the positive surface charge by AU NPs and the photothermal inhibition of cancer cells was investigated.

Unique Spin Vortices and Topological Charges in Quantum Dots with Spin-orbit Couplings

Spin textures of one or two electrons in a quantum dot with Rashba or Dresselhaus spin-orbit couplings reveal several intriguing properties. We show here that even at the single-electron level stable spin vortices with tunable topological charges exist. These topological textures appear in the ground state of the dots. The textures are stabilized by time-reversal symmetry breaking and are robust against the eccentricity of the dot. The topological charge is directly related to the sign of the z component of the spin in a large dot, allowing a direct probe of its topological properties. This would clearly pave the way to possible future topological spintronics. The phenomenon of spin vortices persists for the interacting two-electron dot in the presence of a magnetic field.

Functionalized Two-Dimensional MoS2 with Tunable Charges for Selective Enzyme Inhibition

Recent advances in the synthesis and functionalization of two-dimensional (2D) nanomaterials have allowed us to explore their interaction with biological systems. 2D nanomaterials, owing to their u...

Structure and property of a Cu(II) compound bearing isopolyanion and flexible triol ligand

The investigations of the organic-inorganic hybrid materials attract widely attentions in recent years due to their applications in many fields, such as medicine, magnetism and catalysis. As one of the important types of inorganic components, polyoxometalates (POMs) bear the features of various compositions, rich structures and tunable charges, and play key roles in the construction of hybrid materials. Since the first [Mo7O24]6- polyanion was synthesized and its structure was confirmed by single-crystal X-ray analysis, many different kinds of cations, including inorganic and organic ions, were introduced to this system. While the studies of this type of polyanion with coordination compounds are still rarely, especially for transition metal ions and oxygenated ligands. As our ongoing study in the field of POM-containing compounds, we succeeded in obtaining an organic-inorganic hybrid based on [Mo7O24]6- polyanion in aqueous solution with CuSO4·5H2O, (NH4)6Mo7O24·4H2O and a triol ligand as staring materials. The formula of the obtained compound was determined as (NH4)2[CuL(H2O)]2MO7O24∙3H2O, L=(HOCH2)3CNH(CH2)3NHC(CH2OH)3 ( 1 ) through X-ray analysis, elemental analysis, IR spectrum and TG analysis. Single-crystal X-ray analysis reveals that compound 1 belongs to the monoclinic system with the space group of P 21. The unit cell parameters is a =10.778(2) A, b =21.391(3) A, c =11.596(3) A, α =90°, β =96.82(1)°, γ =90°, V =2654.4(9) A3, Z =2, and the final R 1 is 0.0155. In the crystal structure of compound 1 , Cu2+ cation is in a six-coordination environment and combines with ligand L in the unsymmetrical chelate coordination manner, where two triol groups provide one and two O atoms respectively and the other three positions are occupied by two N atoms and one O atom from water molecule. The [CuL(H2O)]2+ subunit connects with [Mo7O24]6- polyanion through the strong O−H∙∙∙O and N−H∙∙∙O hydrogen bonds to form a supramolecular two-dimensional network. TG curve shows that compound 1 has a good thermal stability until 160°C. The behavior of temperature dependence magnetic susceptibility of compound 1 in the range of 2−300 K expresses a strong antiferromagnetic property. In this work, the flexibility of the ligand plays a key role and provides the possibility for the formation of the unsymmetrical chelate coordination style of Cu2+. In addition, the high charge number of polyanion is an important factor for the construction of the two-dimensional network through providing more interactive sites.

Fabrication and characterization of phosphorylated chitosan nanofiltration membranes with tunable surface charges and improved selectivities

Phosphorylated chitosan (PCS) with tailored amount of phosphate groups was synthesized, and novel composite nanofiltration membranes (NFMs) with tunable surface charges were prepared by coating PCS onto polyacrylonitrile (PAN) supporting layer and subsequently cross-linked by glutaraldehyde (GA). Chemical structures and compositions of PCS and NFMs, along with morphologies, surface charges, and performance of NFMs were represented by using FTIR, TG, ATR-IR, SEM-EDX, AFM, streaming potential analyzer, and cross-flow flat permeation test, respectively. The effect of different phosphorous abundance of PCS precursors on the surface charge and permselectivity of NFMs was investigated systematically. It was illustrated that the incorporation of phosphate group with high-substitute degree did enhance the surface charge and selectivity of NFM, respectively, while retaining its permeability. The resultant membrane showed a zeta potential of −77.6 mV at 1 mol·m−3 KCl electrolyte solution and pH 7.0, significantly more superior than that of the commercial DL membrane. For the feedwater (Na2SO4 + MgCl2, 1.0 g·L−1), the mass ratio of SO42−/Cl− and Mg2+/Na+ decreased from initial 0.5:1 in the feed to 1.58 × 10−2 and 0.254 in the permeate after filtration by the optimal NF membrane. Anionic dyes removal tests also confirmed the existence of negative charge characteristics from the prepared membranes, and pivotal role of the Donnan exclusion in separating performance. In addition, NFM4 exhibits good chemical stability in the long-term operation.

Switchable geometric frustration in an artificial-spin-ice-superconductor heterosystem.

Geometric frustration emerges when local interaction energies in an ordered lattice structure cannot be simultaneously minimized, resulting in a large number of degenerate states. The numerous degenerate configurations may lead to practical applications in microelectronics1, such as data storage, memory and logic2. However, it is difficult to achieve very high degeneracy, especially in a two-dimensional system3,4. Here, we showcase in situ controllable geometric frustration with high degeneracy in a two-dimensional flux-quantum system. We create this in a superconducting thin film placed underneath a reconfigurable artificial-spin-ice structure5. The tunable magnetic charges in the artificial-spin-ice strongly interact with the flux quanta in the superconductor, enabling switching between frustrated and crystallized flux quanta states. The different states have measurable effects on the superconducting critical current profile, which can be reconfigured by precise selection of the spin-ice magnetic state through the application of an external magnetic field. We demonstrate the applicability of these effects by realizing a reprogrammable flux quanta diode. The tailoring of the energy landscape of interacting 'particles' using artificial-spin-ices provides a new paradigm for the design of geometric frustration, which could illuminate a path to control new functionalities in other material systems, such as magnetic skyrmions6, electrons and holes in two-dimensional materials7,8, and topological insulators9, as well as colloids in soft materials10-13.

Highly Confined and Tunable Hyperbolic Phonon Polaritons in Van Der Waals Semiconducting Transition Metal Oxides.

2D van der Waals (vdW) layered polar crystals sustaining phonon polaritons (PhPs) have opened up new avenues for fundamental research and optoelectronic applications in the mid-infrared to terahertz ranges. To date, 2D vdW crystals with PhPs are only experimentally demonstrated in hexagonal boron nitride (hBN) slabs. For optoelectronic and active photonic applications, semiconductors with tunable charges, finite conductivity, and moderate bandgaps are preferred. Here, PhPs are demonstrated with low loss and ultrahigh electromagnetic field confinements in semiconducting vdW α-MoO3 . The α-MoO3 supports strong hyperbolic PhPs in the mid-infrared range, with a damping rate as low as 0.08. The electromagnetic confinements can reach ≈λ0 /120, which can be tailored by altering the thicknesses of the α-MoO3 2D flakes. Furthermore, spatial control over the PhPs is achieved with a metal-ion-intercalation strategy. The results demonstrate α-MoO3 as a new platform for studying hyperbolic PhPs with tunability, which enable switchable mid-infrared nanophotonic devices.

Chemical Design of Both a Glutathione-Sensitive Dimeric Drug Guest and a Glucose-Derived Nanocarrier Host to Achieve Enhanced Osteosarcoma Lung Metastatic Anticancer Selectivity.

Although nanomedicines have been pursued for nearly 20 years, fundamental chemical strategies that seek to optimize both the drug and drug carrier together in a concerted effort remain uncommon yet may be powerful. In this work, two block polymers and one dimeric prodrug molecule were designed to be coassembled into degradable, functional nanocarriers, where the chemistry of each component was defined to accomplish important tasks. The result is a poly(ethylene glycol) (PEG)-protected redox-responsive dimeric paclitaxel (diPTX)-loaded cationic poly(d-glucose carbonate) micelle (diPTX@CPGC). These nanostructures showed tunable sizes and surface charges and displayed controlled PTX drug release profiles in the presence of reducing agents, such as glutathione (GSH) and dithiothreitol (DTT), thereby resulting in significant selectivity for killing cancer cells over healthy cells. Compared to free PTX and diPTX, diPTX@CPGC exhibited improved tumor penetration and significant inhibition of tumor cell growth toward osteosarcoma (OS) lung metastases with minimal side effects both in vitro and in vivo, indicating the promise of diPTX@CPGC as optimized anticancer therapeutic agents for treatment of OS lung metastases.

Design and fabrication of reduction-sensitive cell penetrating nanofibers for enhanced drug efficacy.

This work demonstrates a modular design strategy based on the supramolecular assembly of multidomain peptides to fabricate reduction-responsive cell penetrating nanofibers (CPNs), which hold great promise for selective targeting of cancer therapeutics to tumor cells.

Stable graphene oxide/poly(ethyleneimine) 3D aerogel with tunable surface charge for high performance selective removal of ionic dyes from water

Graphene oxide (GO) with oxygen-containing functional groups views a promising adsorbent to remove cationic pollutants from water. To achieve high removal efficiency of both anionic and cationic pollutants and overcome recycling difficulty of GO, positively charged poly(ethyleneimine) (PEI) was associated with GO to fabricate GO/PEI (GP) 3D aerogels. Surface charges of the constructed GP aerogels were tuned from positive to negative within a wide range via changing solution pH. The constructed GP aerogels were stable in acidic and basic aqueous environments, and even in organic solvents (such as methanol, acetonitrile, methylbenzene, acetone and N,N-dimethyl formamide), which are easily recovered. Anionic methyl orange (MO) and cationic methylene blue (MB) were utilized as model pollutants to investigate the adsorption capability of the GP aerogels. The GP aerogels showed high adsorption capacity for anionic MO (331.0 mg/g) at pH 2.0 while for cationic MB (249.6 mg/g) at pH 10.5. The electrostatic attraction force and π-π interaction dramatically improved the adsorption capacity of the charge-tunable GP aerogels against both anionic and cationic dyes. In addition, the GP aerogels were able to selectively separate anionic and cationic dyes in designed aqueous environments. These aerogels may be used as versatile sorbents for various charged pollutants removal due to tunable surface charges.

Cytotoxicity, chemical stability, and surface properties of ferroelectric ceramics for biomaterials

AbstractSurface chemistry and topo‐physical properties determine the interactions of biomaterials with their physiological environment. Ferroelectrics hold great promise as the next generation of scaffolds for tissue repair since they feature tunable surface electrical charges, piezoelectricity, and sensing capabilities. We investigate the topography, wettability, chemical stability, and cytotoxicity in salient ferroelectric systems such as (1−x) (Na1/2Bi1/2)TiO3–xBaTiO3, (1−x)Ba(Zr0.2Ti0.8)O3−x(Ba0.7Ca0.3)TiO3, and Pb(Zr,Ti)O3 to test their suitability as biomaterials. The lead‐free ferroelectrics promote in vitro cell viability and proliferation to a considerably high extent. 0.94 mol % (Na1/2Bi1/2)TiO3–0.06 mol% BaTiO3 showed the greatest potential leading to a cell viability of (149 ± 30)% and DNA synthesis of (299 ± 85)% in comparison to the reference. Lead leaching from Pb(Zr,Ti)O3 negatively affected the cultured cells. Wettability and chemical stability are key factors that determine the cytotoxicity of ferroelectrics. These variables have to be considered in the design of novel electroactive scaffolds based on ferroelectric ceramics.

X-ray Spectroscopy Uncovering the Effects of Cu Based Nanoparticle Concentration and Structure on Phaseolus vulgaris Germination and Seedling Development.

Nanoparticles properties such as solubility, tunable surface charges, and singular reactivity might be explored to improve the performance of fertilizers. Nevertheless, these unique properties may also bring risks to the environment since the fate of nanoparticles is poorly understood. This study investigated the impact of a range of CuO nanoparticles sizes and concentrations on the germination and seedling development of Phaseolus vulgaris L. Nanoparticles did not affect seed germination, but seedling weight gain was promoted by 100 mg Cu L-1 and inhibited by 1 000 mg Cu L-1 of 25 nm CuO and CuSO4. Most of the Cu taken up remained in the seed coat with Cu hotspots in the hilum. X-ray absorption spectroscopy unraveled that most of the Cu remained in its pristine form. The higher surface reactivity of the 25 nm CuO nanoparticles might be responsible for its deleterious effects. The present study therefore highlights the importance of the nanoparticle structure for its physiological impacts.

Fluorescent carbon dots with tunable negative charges for bio-imaging in bacterial viability assessment

Applying bio-imaging in bacterial viability assessment is vital to human health. Nitrogen, phosphorus co-doped carbon dots (NPCDs) with high visible fluorescence and tunable negative charges were synthesized by a feasible hydrothermal reaction. The as-prepared NPCDs possess abundant surface functional groups, excellent photostability and bio-compatibility. Especially, the surface negative charges of NPCDs can be adjusted by changing the kind of the precursors. The obtained NPCDs as a fluorescent dye could selectively stain dead bacteria instead of live ones due to electrostatic repulsion since the cell walls of bacteria possess negative charges. The NPCDs with less negative charges provides a low accurate mortality rate due to a weaker repulsion, while NPCDs with the most negative charges give a comparable mortality rate with traditional plate counting method but consumes shorter time. Our study suggests that NPCDs with highly negative charges could serve as a precise and efficient fluorescent probe to determine the living state of bacteria, widening the path for bio-imaging application in bacterial viability assessment.

Strong-field ionization of asymmetric triatomic model molecules by few-cycle circularly polarized laser pulses

We have developed a numerical model system for a single active electron in an environment of three nuclei with tunable charges arranged as an equilateral triangle. This enables mimicking of both symmetric and asymmetric nuclear charge configurations, while keeping the ionization potential fixed. We investigate the interaction of these model systems with intense, few-cycle, circularly polarized infrared laser pulses and examine the asymmetries between the photoelectron spectra induced by the left- and right-circularly polarized fields. We show that these asymmetries are influenced by the initial symmetry of nuclear charge configurations. We demonstrate that few-cycle laser pulses can induce an additional asymmetry in the photoelectron spectra, which can weaken or enhance the asymmetry imprinted by the initial symmetry properties of the model system.

LBL assembled polyelectrolyte nanofiltration membranes with tunable surface charges and high permeation by employing a nanosheet sacrificial layer

A novel strategy is developed to fabricate LBL assembled polyelectrolyte nanofiltration membranes with tiny filtration resistance and tunable surface charges and thus leading to high permeation flux and excellent rejections for charged molecules.