Ultrahigh Yield Research Articles

N doped-carbon quantum dots with ultra-high quantum yield photoluminescent property conjugated with folic acid for targeted drug delivery and bioimaging applications

BackgroundImproving targeted therapy, and reducing adverse side effects of antitumor drugs toward normal cells with simultaneous bioimaging properties are being developed in pharmaceutical industries. In this study, N doped-carbon quantum dot (CQD) with ultra-high quantum yield (QY) was synthesized and its surface was modified with folic acid as the targeted anticancer agent. MethodsCQD was synthesized by one-step hydrothermal method. The impact of operating parameters such as pyrolysis temperature, time, and pH on the QY and surface charge was investigated. Then, the CQD surface was modified with folic acid as the targeted anticancer agent followed by doxorubicin (DOX) conjugation on the surface. Cytotoxicity of CQD-FA and CQD-FA-DOX upon 4T1, MCF7 and PC12 cell lines were examined. Furthermore, fluorescent microscopy imaging and flow cytometry analysis for various cell lines were applied to evaluate CQD-FA bioimaging property. In addition, the efficacy of the formulation on the BALB/c mice bearing breast cancer tumors was investigated. ResultsIn CQD preparation, average particle size of 7 nm was confirmed by the characterization results. With optimum synthesis conditions of pH = 11, time = 8 h and temperature = 160 °C, QY was about 90%. XPS analysis confirmed formation of N doped CQD. DOX loading efficiency was 88.6% and about 86% of the loaded DOX was released from CQD-FA-DOX after 72 h at pH = 5.5. Cytotoxicity analysis confirmed a higher toxicity effect of CQD-FA-DOX toward cancerous cell lines (4T1, MCF7) in comparison to free DOX. This nanocarrier could act smartly in identifying folate receptor positive cancerous cells and enter mainly by the receptor-mediated route. In vivo results showed that cellular internalization of CQD-FA-DOX was greater than free DOX, in which the tumor growth in mice treated with CQD-FA-DOX was lower than free DOX. In addition, ex vivo analysis confirmed lower side effects of CQD-FA-DOX on the main organs of mice in comparison to the free drug group. ConclusionThis new synthesized carrier can be a suitable platform for drug delivery applications with lower side effects, targeted cellular uptake and bioimaging properties.

A new transformation-induced plasticity-assisted dual-phase medium-entropy alloy with ultra-high cryogenic mechanical properties

A novel maraging Fe68Ni10Mn10Co10Ti1.5Si0.5 (at%) medium-entropy alloy (MEA) was designed and microstructurally engineered to obtain a superior combination of tensile strength and uniform elongation at liquid nitrogen temperature. To this end, short-time martensite-to-austenite reversion treatment was conducted on an aged specimen to gain a dual-phase microstructure decorated by needle-like (NiMn)3−xTix and the elliptical-shaped Ni2SiTi nano-precipitates. The alloy exhibited an ultra-high yield strength of 1.41 GPa and ultimate tensile strength of 1.88 GPa, with a uniform elongation of ∼14% in the reverted condition. These superior properties are attributed to the transformation-induced plasticity (TRIP)-assisted heterogeneous dual-phase microstructure strengthened by well-distributed nano-precipitates. The metastability-engineering approach to achieve TRIP-assisted maraging MEA can usefully guide design to overcome the strength–ductility trade-off in extreme environments.

Fine-grained 93W-4.9Ni-2.1Fe alloy with ultrahigh yield strength prepared via low temperature sintering of W nanocomposite powder

In this study, to obtain tungsten heavy alloy (WHA, 93W-4.9Ni-2.1Fe) with fine grain, high density and enhanced strength, W–Ni–Fe nanocomposite powder with high sintering driving force and small composite scale was designed and prepared. The effects of sintering temperature on the microstructure and properties of WHAs were systematically investigated. At a relatively low temperature of 1300 °C, WHAs with both high relative density of 98.0±0.31% and fine grain size of 2.07 μm were obtained, which was much smaller than that of traditional WHAs (30–60 μm). This special microstructure made it simultaneously achieve excellent compressive yield strength (1555 MPa), high strain-to-failure (over 40%) and hardness (480 HV0.5). This ultrahigh yield strength was about 2 times as the conventional WHAs with lager grain size. With the further increase of temperature to 1450 °C, the grain size of W grew significantly from 2.07 to 6.57 μm and the yield strength decreased remarkedly to 947 MPa. It was found that the W phase had good interfacial bonding with the γ-(Ni, Fe) matrix phase and the enhanced mechanical properties were mainly contributed by the small grain size and high ratio of phase boundary, which can significantly improve the storage capacity of dislocation.

Designing ultra-strong and ductile hierarchical titanium alloys via interstitial solute-mediated multi-morphologic α-nanoprecipitates

In conventional duplex titanium (Ti) alloys, the soft primary α-precipitates (αp) are beneficial to ductility with the loss of high yield strength, while the continuous α-precipitates at grain boundaries (GBs, αGBs) often accompanied with α precipitate-free zones (α-PFZs) renders the strain incompatibility for limited ductility. Here, to overcome this longstanding issue, we utilize interstitial (O and N) atoms to notably strengthen the α-phase, and simultaneously architect the multi-morphologic secondary α-precipitates (αs) so as to improve the strain compatibility nearby GBs, thus develop a Ti-4.1Al-2.5Zr-2.5Cr-6.8Mo (wt.%) alloy with ultra-high yield strength of ∼1580 MPa and good ductility of ∼8.2%. The phase boundaries between the hard α-precipitates and the soft β-matrix not only act as dislocation barriers for strengthening, but also as sustainable dislocation sources for ductilizing to achieve a good combination of strength and ductility in our Ti alloys. This strategy not only sheds light on the understanding of the strength-ductility synergy of duplex Ti alloys, but also offers an available pathway to design ultra-strong and ductile alloys.

A high-pressure-tolerant vapor-fed photocatalytic system for efficient water splitting

Efficient water-vapor splitting opens up a new strategy for developing scalable and corrosion-free solar-energy-harvesting systems. In a recent issue of Nature Communications, Takanabe and co-workers report a high-pressure-tolerant vapor-fed photocatalytic water-splitting system for highly efficient photocatalytic H2 evolution with an ultrahigh apparent quantum yield of 54% ± 4%.

Electrocatalytic conversion of methane to ethanol by ultrathin WO3 nanosheets: Oxygen vacancy engineering

Electrocatalytic conversion of CH4 into valuable liquid products is an attractive strategy for utilization of natural gas, however, it was still constrained by low product yields. Herein, ultrathin WO3 nanosheets with adequate oxygen vacancies (Ov) as robust electrocatalysts for highly efficient CH4 conversion to ethanol were synthesized. Using the optimized sample, the ultrahigh ethanol yield and selectivity of 125,090 μmol gcat−1 h−1 and 99.4% are achieved within 8 h at low potential of 1.2 V vs. RHE, both of which outperform the previous reports as we know. The corresponding ethanol Faradic efficiencies is 50.7%. In-situ Raman spectra and density functional theory calculation reveal that Ov effectively enable CH activation and CC coupling, and eventually promotes the electrocatalytic activity and ethanol selectivity for CH4 conversion. This work provides a constructive avenue for designing electrocatalysts with both high activity and selectivity to realize CH4 conversion.

Effects of annealing temperature and V addition on microstructure and mechanical properties of Fe-Mn-Al-C austenitic low-density steel

This study investigated the effect of annealing temperature (Ta=800–1000 ℃) on the microstructure and mechanical properties of Fe-25Mn-10Al-1.1 C-(0,0.48)V (wt%) austenitic low-density steels. The results show that Ta has significant influence on the microstructures of the two tested steels. Considerable amount of ferrites and κ-carbides appeared on grain boundaries due to precipitation reaction (γ→α + κ) when annealed at a lower temperature of 800 ℃, and the V addition would promote the precipitation reaction and cause an increase of ferrite content when annealed at no more than 900 ℃. The content of VC reached a maximum at Ta= 900 ℃, which also significantly inhibited the formation of κ-carbide and delayed the recrystallization besides grain refinement for the V-added steel. Moreover, VC also inhibited the development of the Σ3n (n = 1,2,3) boundaries at Ta of no more than 900 ℃. Ultra-high yield strength of 1120 MPa was obtained when the V-added steel was annealed at 900 ℃ mainly due to the drastic VC precipitation. The present work provides a promising strategy to enhance the yield strength of austenitic low-density steel via tailoring Ta and the addition of V.

Cryogenic mechanical behavior of a FeCrNi medium-entropy alloy fabricated by selected laser melting

A single-phase FeCrNi medium-entropy alloy (MEA) with a face-centered cubic structure was successfully fabricated by selected laser melting (SLM). The SLMed FeCrNi MEA exhibits hierarchical microstructures, including molten pools, coarse columnar grains, submicron cellular structures and high-density dislocations, and shows an excellent strength-ductility combination. Notably, the SLMed FeCrNi MEA has ultra-high yield strength and ultimate tensile strength of 1.1 GPa and 1.5 GPa, respectively, at 77 K, which are almost 1.5 times higher than those at room temperature, while still maintaining a high fracture elongation of 49%. It was also found that the SLMed FeCrNi MEA deformed at 77 K could produce more nanotwins compared with that deformed at room temperature. The twinning-prone matrix can produce more significant twinning-induced plasticity effects, which contributes to a high plasticity. Additionally, the high-density cellular substructure can effectively hinder dislocation motion, which is the main reason for the high strength.

Carbon fiber-reinforced composites based on an epoxy resin containing Schiff base with intrinsic anti-flammability, good mechanical strength and recyclability

A new renewable material, comprising a Schiff base epoxy thermoset derived from furan derivatives, was successfully synthesized. This innovative material not only possesses remarkable carbon fiber recyclability but also exhibits favorable mechanical properties and flame retardancy. After being cured with the bio-based curing agent, 5,5′-methylenedifurfurylamine, the cured Schiff base epoxy thermoset exhibited an ultra-high char yield of 54% and a glass transition temperature of 207 °C. Compared to bisphenol A epoxy resin, it achieved a 100% higher yield. Furthermore, the cured Schiff base epoxy thermoset demonstrated a high storage modulus (at 30 °C) of 2695 MPa and a tensile modulus of 60 MPa, surpassing bisphenol A epoxy resin. Remarkably, the exceptional structure of the Schiff base epoxy thermoset imparted intrinsic flame retardancy, resulting in a V-0 rating in the UL-94 test. The thermoset also exhibited considerable recyclability in carbon fiber composites due to its Schiff base network. Moreover, it could be nondestructively and quickly recycled under mildly acidic conditions, enabling efficient recycling of the carbon fiber composites.

Achieving unprecedented yield strength of 2.2 GPa with high ductility in formed parts using strain-aging

Ultra-high yield strength is important in extreme service conditions, but it severely deteriorates the ductility and also brings significant challenges for material forming. Here, we successfully developed a strategy involving the compositionally lean alloy design and strain-aging processing route to endow medium Mn steels with unprecedented ‘part performance’ of 2.0–2.3 GPa yield strengths and 8–14% uniform elongations. The significant bake hardening response with the maximum of 465 MPa higher than the most of existing researches is reported, which leads to the ultra-high yield strength above 2 GPa. By applying pre-strains, the morphology and volume fraction of retained austenite can be tailored, which affects the Lüders bands and the transformation-induced-plasticity (TRIP) effect. In the suitable pre-strain range, the film-like retained austenite with high stability can provide sustained TRIP effect, thus ensuring high uniform elongations in the strain-aged samples.

Rare-earth and transition metal ion single-/co-doped double-perovskite tantalate phosphors: Validation of suitability for versatile applications

Novel rare-earth (RE; e.g., europium (Eu³⁺), samarium (Sm³⁺), and praseodymium (Pr³⁺)) and transition metal (TM⁴⁺; e.g., manganese (Mn⁴⁺)) ion single-/co-doped double-perovskite Ca₂InTaO₆ (CITO) phosphors were prepared and investigated with respect to their crystal structure and photoluminescence (PL) properties. Among them, the CITO:Eu³⁺ phosphors were found to exhibit an ultra-high internal PL quantum yield (89.1%) and good thermal stability (78.7% at 423 K relative to the initial value at 303 K). As such, the corresponding packaged white light-emitting diode (LED) was able to display a remarkable color rendering index (CRI; = 91.51@10 mA). Besides, the potential in applications of anti-counterfeiting fields and a novel LED structure based on flexible phosphor-converted films was also studied. Moreover, due to their different thermal quenching, trivalent lanthanide (Ln³⁺)/Mn⁴⁺ co-doped CITO phosphors were designed for optical thermometry based on the luminescence intensity ratio (LIR) between different 4f transitions of various Ln³⁺ ions and ²E_g → ⁴A_2g (Mn⁴⁺) transition. Particularly, the LIR between the ⁴G_5/2 → ⁶H_9/2 and ²E_g → ⁴A_2g peaks of the CITO activated with 5 mol% Sm³⁺ and 0.3 mol% Mn⁴⁺ exhibited the most excellent relative sensitivity (<i>S</i>_r; = 3.80 %·K⁻¹) with beneficial temperature uncertainty of 0.0648 K. Overall, these results are of significance to offer valuable databases for constructing multifunctional high-performance optical platforms using single-/co-doped double-perovskite tantalates.

Annealing-induced abnormally ultrahigh cryogenic strength-ductility synergy in a cold rolled ferrous medium entropy alloy

Using cold rolling and low temperature annealing, a Fe65Ni15Cr10Co10 medium entropy alloy (MEA) with a heterogeneous microstructure was presented. The cold rolled and low temperature annealed specimen display an abnormally ultrahigh yield strength and ductility at −196 °C, compared to the cold rolled specimen. The underlying mechanism are mainly attributed to a synergy of hetero-deformation induced (HDI) strengthening, boundary strengthening and transformation-induced plasticity (TRIP) effect.

Alcohol Solvent Assisted Synthesis of Metallic and Metal Oxide Catalysts: As-Prepared Cu/ZnO/Al2O3 Catalysts for Low-Temperature Methanol Synthesis with an Ultrahigh Yield

Alcohol Solvent Assisted Synthesis of Metallic and Metal Oxide Catalysts: As-Prepared Cu/ZnO/Al₂O₃ Catalysts for Low-Temperature Methanol Synthesis with an Ultrahigh Yield

Plasmonic Au nanoparticles anchored 2D WS2@RGO for high-performance photoelectrochemical nitrogen reduction to ammonia

The photoelectrochemical reduction of nitrogen to ammonia (NH3) is a sustainable and cost-effective process. The photoelectrocatalysts adsorb light, activate N2, and transport electrons efficiently to achieve high-yield NH3. In the present work, gold-tungsten sulfide-anchored reduced graphene oxides (Au-WS2@RGO) are developed as highly efficient photoelectrocatalysts for the N2 reduction reaction (NRR) to synthesize NH3. The effect of Au nanoparticles loaded on WS2@RGO is optimized to achieve hierarchical 2D Au-WS2@RGO with excellent electrical conductivity, large active surface area, and unique porous network. Photoelectrocatalytic NRR of Au-WS2@RGO achieves remarkable NH3 production rates with ultrahigh NH3 yield of 34 μgh-1mgcat-1 at −0.6 V, tremendous faradaic efficiency (FE) of 16.2 %, long durability for about 14 h, and prolonged lifetime of photo-carriers. DFT calculations support the experimental findings and demonstrate that Au-WS2@RGO as an effeient NRR catalyst with low overpotential. The Au-WS2@RGO shows the highest NRR performances even in atmospheric air (AirRR) and outperforms the state-of-the-art NRR catalysts. The high AirRR performance and durability of Au-WS2@RGO make it a promising alternative to Au-based NRR catalysts in photo electrolyzers. Further, an innovative methodology will be proposed for high-efficiency urea fertilizer production using Au-WS2@RGO-based NRR photocatalysts.

Hierarchical precipitates facilitate the excellent strength-ductility synergy in a CoCrNi-based medium-entropy alloy

An interstitial carbon-doped CoCrNiSi0.3 medium-entropy alloy (MEA) has been developed, which exhibits excellent strength-ductility synergy. This has been achieved through the implementation of a three-level hierarchical-precipitate-microstructure design. The CoCrNiSi0.3C0.048 MEA displays an ultra-high yield strength of 1.34 GPa, accompanied by a uniform tensile elongation of 8.62%, surpassing the performance of most carbon/silicon-doped MEAs. The three-level hierarchical precipitate structure comprises the primary Cr23C6 carbides (2–10 μm), the secondary SiC precipitates (200–500 nm) surrounding the grain boundaries, and the tertiary SiC precipitates (∼50 nm) within the grains. The strengthening and toughening behavior of the current MEAs are attributed to multiple mechanisms, including crack branching and blunting in Cr23C6 carbides, dislocation-bypass mechanism around the non-shearable SiC precipitates, hetero-deformation-induced strengthening caused by the interface between matrix/three-level hierarchical precipitates, as well as stacking-fault networks and dense nanotwins activated by precipitates in the matrix. These findings provide valuable insights into the development of high-performance alloys for engineering applications in the future.

Band Position-independent Piezo-electrocatalysis for Ultrahigh CO2 Conversion.

Piezo-electrocatalysis as an emerging mechano-to-chemistry energy conversion technique opens multiple innovative opportunities and draws great interest over the past decade. However, the two potential mechanisms in piezo-electrocatalysis, i.e., screening charge effect and energy band theory, generally coexist in the most piezoelectrics, making the essential mechanism remain controversial. Here, for the first time, we distinguish the two mechanisms in piezo-electrocatalytic CO2 reduction reaction (PECRR) through a narrow-bandgap piezo-electrocatalyst strategy using MoS2 nanoflakes as demo. With conduction band of -0.12eV, the MoS2 nanoflakes are unsatisfied for CO2 -to-CO redox potential of -0.53eV, yet they achieve an ultrahigh CO yield of ∼ 543.1 μmol·g-1 ·h-1 in PECRR. Potential band position shifts under vibration are still unsatisfied with CO2 -to-CO potential verified by a combination analysis of theoretical investigation and piezo-photocatalytic experiment, further indicating that the mechanism of piezo-electrocatalysis is independent of band position. Besides, MoS2 nanoflakes exhibit unexpected intense "breathing" effect under vibration and enable the naked-eye-visible inhalation of CO2 gas, independently achieving the complete carbon cycle chain from CO2 capture to conversion. The CO2 inhalation and conversion processes in PECRR are revealed by a self-designed in situ reaction cell. This work brings new insights into the essential mechanism and surface reaction evolution of piezo-electrocatalysis. This article is protected by copyright. All rights reserved.

Achieving purple light excitable high-efficiency temperature-responsive dual- and single-mode afterglow in carbon dots

Afterglow materials including thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) have inspired extensive attention and research in anti-counterfeiting and sensing application prospects. However, a critical challenge currently remains within this afterglow materials only exhibit single-mode phosphorescence or delayed fluorescence with a persistent luminescence but low quantum yield. In this study, carbon dots composites with long-lived afterglow and ultra-high afterglow quantum yields of 193.5 ms and 35.07% were obtained by embedding the luminescent centers of ciprofloxacin into the formed rigid boric acid matrix by a one-step hydrothermal with purple light as the excitation wavelength. It is worth mentioning that the constructed composites exhibit dual-mode afterglow (DF and RTP) features at room temperature. Moreover, the carbon dots composites have distinctive temperature-responsive color-tunable properties and represent afterglow emission dominated by delayed fluorescence or phosphorescence at different temperatures. Based on the extraordinary temperature sensitivity, a single-mode ultra-long phosphorescence with a lifetime of up to 1.11 s is achieved at low temperatures. Additionally, as-prepared carbon dots composites exhibit the afterglow quantum yield of 40.97% in CB-VII, which is an ultra-high value for inorganic non-metallic materials. Furthermore, the resultant composites of carbon dots with new potential materials of encryption technology are designed for advanced information encryption and anti-counterfeiting applications.

Effect of Tempering Temperature on the Microstructure, Deformation and Fracture Properties of an Ultrahigh Strength Medium‐Mn Steel Processed by Quenching and Tempering

Herein, a medium‐Mn steel containing 4 wt% Mn is designed to achieve ultrahigh tensile strength and good ductility by the quenching and tempering process. The effects of tempering temperature on the microstructure, tensile behavior, and fracture properties under different stress states are explored. It is observed that tempering temperature influences the fracture mechanisms of the ultrahigh‐strength steels. Both ductile fracture strain and cleavage fracture strength of the investigated medium‐Mn steel are affected by the tempering temperature. The impacts of tempering temperature on volume fraction, carbon content of retained austenite (RA), and tensile properties are quantitatively analyzed. Detailed microstructure analysis reveals that both volume fraction and carbon content of the RA are increased in the tempered steels, accompanied by improved tensile properties than in quenched conditions. The superior tensile properties are achieved after tempering at 250 °C, with the ultrahigh yield strength of 1590 MPa, ultrahigh tensile strength of 1963 MPa, and total elongation of 12%. The corresponding relationship between microstructure and mechanical properties is investigated, with a focus on the change of residual stress, the occurrence of carbon redistribution/carbide precipitation, the decrease of dislocation density of martensite, and the presence of transformation‐induced plasticity effect during deformation.

Copper Organometallic Iodide Arrays for Efficient X-ray Imaging Scintillators.

Lead-free organic metal halide scintillators with low-dimensional electronic structures have demonstrated great potential in X-ray detection and imaging due to their excellent optoelectronic properties. Herein, the zero-dimensional organic copper halide (18-crown-6)2Na2(H2O)3Cu4I6 (CNCI) which exhibits negligible self-absorption and near-unity green-light emission was successfully deployed into X-ray imaging scintillators with outstanding X-ray sensitivity and imaging resolution. In particular, we fabricated a CNCI/polymer composite scintillator with an ultrahigh light yield of ∼109,000 photons/MeV, representing one of the highest values reported so far for scintillation materials. In addition, an ultralow detection limit of 59.4 nGy/s was achieved, which is approximately 92 times lower than the dosage for a standard medical examination. Moreover, the spatial imaging resolution of the CNCI scintillator was further improved by using a silicon template due to the wave-guiding of light through CNCI-filled pores. The pixelated CNCI-silicon array scintillation screen displays an impressive spatial resolution of 24.8 line pairs per millimeter (lp/mm) compared to the resolution of 16.3 lp/mm for CNCI-polymer film screens, representing the highest resolutions reported so far for organometallic-based X-ray imaging screens. This design represents a new approach to fabricating high-performance X-ray imaging scintillators based on organic metal halides for applications in medical radiography and security screening.

Microstructure characterization and mechanical properties of AB-typed high-entropy intermetallics with high strength and thermal stability

In this work, we developed a new system of AB-typed high-entropy intermetallics (HEIs) based on CoHf-like B2 crystal structure. The microstructure and mechanical properties of the targeted CoxCuxTiZrHf alloys were detailedly investigated. With the increase of CoCu content, the alloys’ structure changes from multiphase to single phase. In particular, the multi-principal Co1.7Cu1.7TiZrHf alloy with single B2 crystal structure shows ultrahigh compressive yield strength of 1.77 Gpa and fracture strength of 2.15 Gpa at room temperature, as well as high elastic strain limit of approximately 1.5%. Moreover, it can maintain single-phase B2 structure and high strength after annealing at 900 °C.