Single Doping Research Articles

Interfacial Defect Engineering Triggered by Single Atom Doping for Highly Efficient Electrocatalytic Nitrate Reduction to Ammonia

Electrochemical reduction of nitrate (NO3RR), a widespread water pollutant, to high-valued ammonia is encouraging for sustainable artificial nutrient recycling and environmental-friendly pollution management. However, the limited available catalytic active sites and competitive hydrogen evolution make the catalytic performance still unsatisfactory. In this work, interfacial defect engineering via single atom doping was conducted to achieve highly efficient electrocatalytic NO3RR. Upon introduction of isolated Fe atoms, abundant oxygen vacancies are generated over atomic interface of TiO2, and the induced charge redistribution triggers the formation of considerable active sites for nitrate reduction, which plays a crucial role in inhibiting the proton reduction and promoting the adsorption and activation of nitrate. As expected, single atom Fe modified TiO2 exhibits a maximum ammonia yield rate of 137.3 mg h–1 mgcat.–1 and a Faradaic efficiency of 92.3% at −1.4 V (vs RHE), which are among the best of all the reported values yet. This work provides valuable insights into the exploration of highly efficient electrocatalysts toward nitrate reduction through the heteroatom doping and defect engineering over atomic interface.

Nitrogen and fluoride co-doped graphdiyne with metal-organic framework (MOF)-derived NiCo2O4–Co3O4 nanocages as sensing layers for ultra-sensitive pesticide detection

Heteroatom doped graphdiyne (GDY) has been demonstrated to be an effective strategy for achieving outstanding electrochemical properties, including improved electrocatalytic activity, tunable electronic properties and high electronic conductivity, by producing numerous heteroatomic defects as well as active sites. Extensive efforts have been devoted to the issue of single element doping of GDY. Introducing two or more kinds of heteroatoms into GDY materials may create a synergic effect between the co-dopants, thus generating superior electrochemical performance. Nevertheless, little research on multiple elements co-doped GDY, especially in the application of constructing electrochemical biosensor. Herein, nitrogen and fluoride co-doped GDY (N–F-GDY) has been synthesized and employed to combine with NiCo2O4–Co3O4 hollow multishelled nanocages to establish an ultrasensitive electrochemical biosensor for the assay of pesticide residue. The as-prepared electrochemical biosensor possesses a wide linear range of 0.448 pM–44.8 nM for monocrotophos detection and a low detection limit of 0.0166 fM (S/N = 3).

Slightly doped hydroxyapatite pigments of subtractive color with high near-infrared reflectance

A novel series of high near-infrared (NIR) reflective Ca5(PO4)3OH based pigments were synthesized by a solid-phase method. Slight single doping of Fe, Mn, and Cu can change white hydroxyapatite into yellow-orange, cyan, and red-violet, respectively. In the apatite-type structure, Fe ions would occupy the site of the Ca2+, Mn ions preferred to form MnO43− in place of PO43−, and Cu ions tended to stay in the hexagonal channel substituting the protons of OH−. When two of the elements were introduced into hydroxyapatite, the color of the co-doped materials followed the principle of subtractive color mixture. Because of the extremely low concentration of dopant, the structure of hydroxyapatite was kept undisturbed, and its high NIR reflectance was also maintained. This paper discussed chromatic properties, spectral analysis, crystalline structure, and morphology of both single-doped and co-doped samples. The economics, environment-friendly, and colorful Ca5(PO4)3OH based material is a potential cool pigment.

Exploiting underlying crystal lattice for efficient computation of Coulomb matrix elements in multi-million atoms nanostructures

Atomistic modeling of nanostructures often leads to computationally challenging problems involving millions of atoms and tens of thousands of Coulomb matrix elements. In our previous work, we presented a practical solution to this problem, where quasi-linear efficiency, both in time and memory, was obtained by utilizing the fast Fourier transform. Here, we present an updated version of our highly-parallelized computer program, named Coulombo-Lattice, that eliminates the necessity of introducing an auxiliary basis set for the wave-function transfer to the computational grid. Here, we instead exploit the properties of the underlying crystal lattice and run calculations on a regular three-dimensional grid superimposed on the original, lower-symmetry lattice. Due to removal of spurious interactions from other supercells, the resulting Coulomb matrix elements are, up to numerical precision, identical to those obtained by the direct summation O(N2) method, yet our code maintains O(Nlog⁡N) scaling. We illustrate our approach by calculations involving up to 1.7 million integrals, and number of atoms reaching up to 2.8 million, for the problem of dopant charging energy for a single phosphorus dopant embedded in a silicon lattice. Next, to emphasize the broad applicability of our code, we show the results for mixed zinc-blend/wurtzite lattice systems, also known as crystal phase quantum dots. Program summaryProgram Title: Coulombo-LatticeCPC Library link to program files:https://doi.org/10.17632/jwkvh5ycbf.1Licensing provisions: CC BY 4.0Programming language: C++Nature of problem: Computing the Coulomb matrix elements (Coulomb and exchange integrals), while being a demanding computational task, is a necessary step in a range of quantum mechanical calculations. For example, in the field of nanostructures, such as quantum dots and nanowires or novel single dopant devices, this stage of calculation (even after a series of approximations) is at least an O(N2) operation (a summation over all pairs of N atoms or grid points in the analyzed system). Moreover, calculating the full Coulomb matrix usually requires the computation of thousands of such elements, thus presenting a formidable computational challenge.Solution method: We provide a ready-to-use implementation for calculating Coulomb matrix elements for a given set of input wavefunctions in LCAO (linear combination of atomic orbitals) form resulting from tight-binding calculation. This implementation is based on the approach introduced in [1,2], by using a fast Fourier transform. In this work, we further significantly improved the method by eliminating the need to introduce wave-function transfer via auxiliary basis set.Additional comments including Restrictions and Unusual features: The implementation is fully parallelized in a distributed-memory model, using MPI and parallel routines from FFTW [3].

Single Cu Atom Doping on Au11 Nanocluster: Its Implication toward Selectivity in C–C Coupling Reaction

Atom precise metal nanoclusters with customized surface structures are important for understanding the mechanism of surface engineering for appropriate applications. We are reporting a single copper doping on a very widely studied Au11(PPh3)7Cl3 nanocluster, in which one chloride ligand is replaced by one Cu atom. Accordingly, a new bimetal nanocluster Cu1Au11(PPh3)7Cl2 is produced, which consisted of a unique Au–Cu surface motif where the Cu is only bonded with an Au atom. In such a motif, the unsaturated Cu atom acts as an active catalyst for the Sonogashira reaction in contrast to the catalytically inactive Au11 nanocluster. Moreover, it demonstrated a reversed selectivity in the Sonogashira cross-coupling reaction, where the major product obtained was homocoupled Glaser products in contrast to the selectivity of previously reported cluster/bimetallic clusters toward Ullmann or Sonogashira products. Theoretical calculations support the unsaturated Cu to be the active site on the nanocluster (NC) and act like a single-atom catalyst. This highlights the effect of mono copper atom doping on the unique selectivity in the Sonogashira cross-coupling reaction.

Comparison of lithium sulphate borate glass cathode materials with single Mn and Co doping and dual Mn–Co doping

Single Mn and Co doping to dual Co and Mn ions in lithium sulphate (Li2S) borate-based glasses system is carefully studied as new glass cathode for future Li-ion battery. The B–O bonding in glass network and the oxidation states of Co, Mn and S ions in glass structure are investigated using synchrotron-based IR spectroscopy and XANES. The pseudo-capacitance behavior of the CV curves indicates and confirms that Co2+/Co3+ and Mn2+/Mn3+ are in mixed oxidation states. Surprisingly, in this work, the 3Mn5Co glass composition exhibits the highest specific capacitance value of 121.12 F g−1. This shows a better enhancement of electrochemical properties using dual Mn–Co doping in glass structure rather than a single doping.

Benchmarking electrodes modified with bi-doped polypyrrole for sensing applications

Polypyrrole-modified electrodes bi-doped with salicylate and perchlorate anions were synthetized, characterized, and benchmarked according to their ability to meet a set of performance criteria, with the aim of obtaining the best potential candidate for the development of electrochemical sensors. Bi-doped PPy films (PPy-DA) were assessed as compared to those resulting from electropolymerization in solutions providing a single doping anion, namely salicylate (PPy-Sa) or perchlorate (PPy-ClO4−) solutions. Morphological and spectroscopic characteristics of the different polymer films were determined by means of SEM and XPS and Raman spectroscopies. The electrochemical response and electrocatalytic activity of PPy-DA electrodes were characterized by chronoamperometric, voltammetric and electrochemical impedance spectroscopy (EIS) measurements. EIS appeared as a singular tool for determining the conditions where electrochemical response is either dictated by the redox process of the polymer film or governed by a redox couple in solution, and for comparing the electrocatalytic activity of the films without the requirement of knowing the real active electrode area. Comparison was also made among PPy-DA films synthesized by varying dopant concentration in the polymerization bath and electropolymerization time. The presence of salicylate ions favored the formation of films with a three-dimensional tubular structure whereas perchlorate ions contribute to increase their conductivity and electrocatalytic activity. The tubular three-dimensional structure of the electrode surface exhibits an open extended-area pattern that is highly suitable for the electrodeposition of gold nanoparticles (AuNPs), offering new possibilities for developing electrodes for voltammetric sensing. Accordingly, electrodes modified with PPy-DA films decorated with AuNPs were successfully tested for hydrazine determination.

Effects of Codoping on Site-Dependent Eu3+ Luminescence in Perovskite-Type Calcium Zirconate and Hafnate

The single doping of Eu3+ and codoping with Ga3+ or La3+ into perovskite (ABO3)-type CaZrO3 and CaHfO3 were carried out to investigate the effect of codoping on the photoluminescence (PL) features of Eu3+, attempting the site-selective Eu3+ doping at either A or B sites. To comprehend the Eu3+ PL features, the accurate locations of Eu3+ were examined by X-ray absorption near edge structure (XANES) and the proportions of Eu3+ located at A or B sites (Eu3+(A) or Eu3+(B); EuCa• or EuZr'/EuHf') were analyzed. No considerable differences in the XANES spectra and in the proportions of Eu3+(A) and Eu3+(B) were observed in the single-doped samples. On the other hand, the shape of the XANES spectra and the Eu3+ proportion markedly differed in the codoped samples. Ga3+ codoping (GaZr'/GaHf') achieved Eu3+(A) proportions of more than 90%, and La3+ codoping (LaCa•) resulted in the largest Eu3+(B) proportions of approximately 40%. In both PL and PL excitation spectra, the site-dependent spectral features were changed depending on the proportion of Eu3+(A) and Eu3+(B), especially the PL peaks at 595 nm were intensified most in the La3+ codoped samples. Consequently, the site-dependent Eu3+ PL features in CZO and CHO were found to become more conspicuous by the effect of Ga3+ or La3+ codoping. The results also revealed that the codoped ions work not only to compensate for the charge of aliovalent Eu3+ but also to drive Eu3+ to the intentional doping sites.

Effect and mechanism of rare Earth and alkaline Earth metals on the high-temperature stability of activated alumina

Active alumina (Al2O3) is one of the carrier materials used for the purification of automobile exhaust. The crystal transformation of active Al2O3 is due to the high temperature of the automobile exhaust port, which greatly reduces the specific surface area and affects the catalytic efficiency. To improve the high-temperature stability of active Al2O3, this study synthesized Al2O3via the gel-sol method. The influence of rare Earth and alkaline Earth metal doping modification on the high-temperature stability of activated Al2O3 was investigated. The specific surface areas were analyzed using Brunauer–Emmett–Teller, X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning electron microscopy, and transmission electron microscopy to explore the effects and mechanism of different contents of La, Ce, and Ba on active Al2O3. The results showed that suitable single doping of La, Ce, and Ba inhibited the phase transition of Al2O3 and improved the high-temperature stability of active Al2O3. When 1% of La and Ba were mixed and doped into active Al2O3, the specific surface area of the sample after aging at 1,100°C for 4 h was 119.2512 m2/g. X-ray diffraction analysis revealed the agglomeration of Ba atoms inside the alumina and that the incorporated La atoms accelerated the agglomeration and promoted the formation of BaAl2O4.

Theoretical calculation of hydrogen evolution reaction in two-dimensional As2X3(X=S, Se, Te) doped with transition metal atoms

In this paper, density functional theory (DFT) was used to investigate the hydrogen evolution reaction (HER) performance of vacant As2X3(X = S, Se, Te), which is doped with transition metals (TM = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu). The results show that the X-vacancy of As2X3 is stable and can tune the HER activity. According to the scaling relation of Gibbs free energy variation of H* intermediate, the volcano diagram and exchange current density diagram are established. The Co@As2S3 (ΔGH∗ = -0.09 eV), Co@As2Se3 (ΔGH∗ = -0.06 eV) and Cu@As2Te3 (ΔGH∗ = 0.04 eV) systems show good HER performance. Therefore, our research highlights an efficient electrocatalyst for HER with single transition metal atom doping based on As2X3 systems.

Ab-initio study of tuning the electronic and magnetic properties of [formula omitted] Heusler alloy by Co and Mn compound doping

We report the effects of Mn and Co doping on the electronic properties, magnetic exchange interaction, and Curie temperature of intermetallic Ni2MnGa by Green’s function based Korringa–Kohn–Rostoker method with coherent potential approximation(KKR-CPA). The effect of single and compound doping of Mn and Co at different crystallographic positions on these properties are evaluated by computing the electronic and magnetic structures of Ni2MnGa. The study revealed the possibility of tuning magnetic exchange interaction(Jij) and Curie temperature(TC) upon doping. Moreover, it is noted that doping can stabilize the Jahn–Teller distortion. It is also worth noting that TC responds in a different way with concentration as well as the site of the dopant. This study helps in understanding and realizing the cause for magnetic properties in Ni2MnGa, and experimental peers can also use it for further research on doped Ni2MnGa.

Thermoelectric Properties of Nickel and Selenium Co-Doped Tetrahedrite.

As the search continues for novel, cheaper, more sustainable, and environmentally friendly thermoelectric materials in order to expand the range of applications of thermoelectric devices, the tetrahedrite mineral (Cu12Sb4S13) stands out as a potential candidate due to its high abundance, low toxicity, and good thermoelectric performance. Unfortunately, as most current thermoelectric materials achieve zTs above 1.0, ternary tetrahedrite is not a suitable alternative. Still, improvement of its thermoelectric performance has been achieved to zTs ≈ 1 via isovalent doping and composition tuning, but most studies were limited to a single doping element. This project explores the effects of simultaneous doping with nickel and selenium in the thermoelectric properties of tetrahedrite. Simulated properties for different stoichiometric contents of these dopants, as well as the measured thermoelectric properties of the correspondent materials, are reported. One of the samples, Cu11.5Ni0.5Sb4S12.5Se0.5, stands out with a high power factor = 1279.99 µW/m·K2 at 300 K. After estimating the thermal conductivity, a zT = 0.325 at 300 K was obtained for this composition, which is the highest for tetrahedrites for this temperature. However, analysis of the weighted mobility shows the presence of detrimental factors, such as grain boundaries, disorder, or ionized impurity scattering, pointing to the possibility of further improvements.

Effect of Fe3+ and/or PO43– Doping on the Electrochemical Performance of LiNi0.5Mn1.5O4 Cathode Material for Li-Ion Batteries

An Fe3+/PO43– codoped LiNi0.5Mn1.4667Fe0.02P0.0133O4 sample has been prepared by a coprecipitation–hydrothermal method followed by two-step calcination. A novel wet chemical route, using FeSO4 rather than Fe2(SO4)3 as the Fe3+ source and NaH2PO4 as the PO43– source, is adopted to obtain uniform codoping of Fe3+ and PO43– ions in a carbonate precursor according to the precipitation–dissolution–transformation mechanism. For comparison, Fe3+-doped and PO43–-doped samples have been also synthesized via the same route. The effects of Fe3+/PO43– codoping and single doping on the crystalline structure, morphology, and electrochemical performance of LiNi0.5Mn1.5O4 are investigated. Compared with pristine and single doped samples, the codoped sample shows better electrochemical performance, with a specific discharge capacity of 125.2 mAh g–1 at 10 C and a capacity retention rate of 85.9% after 200 cycles at 1 C, under the synergy of Fe3+/PO43– codoping, including enhanced crystallinity, decreased Mn3+ content, significantly reduced primary particle size and secondary agglomeration, as well as the appearance of (110) surfaces in truncated octahedral primary particles.

Theoretical identification of the superior anchoring effect and electrochemical performance of Ti2CS2 by single atom Zn doping for lithium-sulfur batteries.

As one of the promising next-generation energy storage systems, lithium-sulfur (Li-S) batteries have been the subject of much recent attention. However, the polysulfide shuttle effect remains problematic owing to the dissolution of intermediate polysulfide species in the electrolyte and the sluggish reaction dynamics in Li-S batteries. To overcome these issues, this work reports an effective strategy for enhancing the electrochemical performance of Li-S batteries using single atom Zn doping on the S-terminated Ti2C MXenes (Ti2-xZnxCS2). Spin-polarized density functional theory (DFT) calculations were performed to elucidate the interactions of lithium polysulfides (LiPSs) and the Ti2-xZnxCS2 surface in terms of geometric and electronic properties, as well as the delithiation process of Li2S on the Ti2-xZnxCS2 surface. It is found that doping single atom Zn could induce a new Lewis acid-based sites, which could provide proper affinity toward LiPSs. Combined with the metallic character, a low Li diffusion barrier and high catalytic activity for the delithiation process of Li2S, makes Ti2-xZnxCS2 a promising cathode material for Li-S batteries. The results demonstrate the importance of surface chemistry and the electronic structure of MXenes in LiPSs' adsorption and catalysis capability. We believe that our findings provide insights into the recent experimental results and guidance for the preparation and practical application of MXenes in Li-S batteries.

Crystal structural and photoluminescence properties of Eu3+ doped MgZn2(PO4)2 phosphors by R+ (R = Li, Na, K) charge compensation

The effect of the charge compensation agent R+ (R = Li, Na, K) on the luminescence properties of MgZn2(PO4)2:Eu3+ phosphors.

Theoretical expolartion of site selective Perovskites for the application of electronic and optoresponsive memory devices

Now a days, the advent of energy efficient artificial neuromorphic hardware is facing variability and uniformity related state of art issues. DFT deals with this plethora at the atomistic level by introducing innovative composites of improved neuromorphic performance. In this theoretical study unprecedented potential of non-toxic and high dielectric strength of BaHfO 3 is investigated for storage devices. For improving the variability and uniformity related state of art issues, the influence of substitutional doping ofsingle rare earth metal cation at “A” (Ba atom) and “B” (Hf atom) sites of the studied cubic ABO 3 supercell is explored in formation of conducting filaments (CFs). Formation of strongly confined CFs in BaHf 1-x SmO 3 will provide an intriguing roadmap for practical application by resolving the variability and uniformity issues in electronic and optoresponsive memory devices. Alterations of structural and electronic properties by single rare earth dopants will assist in understanding the filamentary based resistive switching in BaHfO 3 . Change in resistance state caused by incident photon stimuli based extrinsic trigger revealed the intriguing neuromorphic nature of BaHfO 3 . The findings of this study will enrich the research exploring the perovskite based resistive switching materials for low power consuming resistive random access memory devices in neuromorphic applications. • The electronic modification subsequently with the creation of the rare earth metal (REM) ion dopant in cubic BaHfO 3 using Perdew-Burke-Ernzerhof Generalized gradient approximation (PBE-GGA) in addition to Hubbered parameter (GGA + U) are performed to investigate the A (Ba atom) and B (Hf atom) site impact of REM (Ce, La, Sm) dopant for switching process and application of optoelectronic devices. • Electronic properties showed sensitivity towards A and B site doping. • Integrated charge density plots depicted charge transfer mechanism. • The conductivity of the phases increased with substitutional replacement of A and B site atom by REM; and eventually resulted that the considered phase opted for low resistance state. • BaHf (1-x) Sm x O 3 is found to be composite with better optoelectronic properties.

Semiconducting SWCNT Photo Detector for High Speed Switching Through Single Halo Doping

The method opted for accuracy, and no existing studies are based on this method. A design and characteristic survey of a new small band gap semiconducting Single Wall Carbon Nano Tube (SWCNT) Field Effect Transistor as a photodetector is carried out. In the proposed device, better performance is achieved by increasing the diameter and introducing a new single halo (SH) doping in the channel length of the CNTFET device. This paper is a study and analysis of the performance of a Carbon Nano Tube Field Effect Transistor (CNTFET) as a photodetector using the self-consistent Poisson and Green function method. The 2D self-consistent Poisson and Green’s function method for various optical intensities and wavelength simulate this proposed photodetector. The performance study is based on the simulation of drain current, transconductance, sub-threshold swing, cut-off frequency, gain, directivity, and quantum efficiency under dark and illuminated conditions. These quantum simulation results show that cut-off frequency increases while there is an increase in diameter. The proposed SH-CNTFET provides better performance in terms of higher gain and directivity than conventional CNTFET (C-CNTFET). This device will be helpful in optoelectronic integrated circuits (OEIC) receivers due to its superior performance.

Formulating a heterolytic cleavage process of water on Ni3N nanosheets through single transition metal doping for ultra-efficient alkaline hydrogen evolution

The effect of transition metal doping on the HER performance of Ni3N was evaluated by experiments and DFT.

Theoretical screening of single atom doping on β-Ga2O3 (100) for photoelectrochemical water splitting with high activity and low limiting potential.

Photoelectrochemical (PEC) water splitting combined with renewable energy is an appealing approach for solar energy conversion and storage. Monoclinic gallium oxide (β-Ga2O3) has been identified as a promising photoelectrode for PEC because of its good electrical conductivity and chemical and thermal stability. However, the wide bandgap (around 4.8 eV) and the recombination of photogenerated electrons and holes inside β-Ga2O3 limit its performance. Doping β-Ga2O3 is a practical strategy to enhance photocatalytic activity, but studies on doped β-Ga2O3 based photoelectrodes are lacking. In this study, we evaluate the doping effect of ten different dopants for β-Ga2O3 photoelectrode at the atomic level using density functional theory calculations. In addition, the oxygen evolution performance is evaluated on doped structures as it is considered the bottleneck reaction in water slitting on the anode of the PEC cell. Our results suggest that rhodium doping is optimal as it demonstrated the lowest overpotential for oxygen evolution reaction. We performed further electronic structure analysis, indicating the narrower bandgap and enhanced photogenerated electron-hole transfer comparing with β-Ga2O3 are the main reasons for the improved performance after Rh doping. This study demonstrates that doping is an attractive strategy for the development of efficient Ga2O3-based photoanodes and it will be of great importance in helping the design of other semiconductor-based photoelectrodes for practical application.

Strong metal-support interactions for high sintering resistance of Ru-based catalysts toward the HER and ORR.

B, N co-doped carbon-supported small-sized Ru nanoparticles (RuBCN) were constructed by a facile ion exchange strategy using closo-[B12H12]2- and Ru(bpy)32+ as the precursors. Benefitting from strong metal-support interactions caused by the synergistic coupling effect of co-dopants B and N, RuBCN exhibits improved sintering resistance and the Ru nanoparticles are stabilized at sub-3 nm at 900 °C. Besides, introducing B doping further increases the electron deficiency of Ru in RuBCN, which could weaken the interaction between Ru and Had species or O2 adsorption. As a result, it exhibits impressive HER (η10 = 20 mV) and ORR (E1/2 = 0.76 V) catalytic performances, as well as outstanding stability, which are much higher than those of the single dopant counterpart.