Undoped Surface Research Articles

Effective Screening of Metal Dopants for In2O3 Catalyst to Tune Catalytic Performance of CO2 Hydrogenation to Formic Acid

The metal doping is an effective strategy to adjust catalytic performance for indium oxide catalyst in CO2 hydrogenation. In current work, a series dopant, Co, Fe, Ni, Pd, Pt, Rh and Ru, are selected and examined in CO2 hydrogenation to formic acid by DFT based microkinetic simulation. It is found that substitutional doping is local effect which mainly promotes the reactivity of adjacent oxygen atoms. The calculations of both CO2 adsorption and hydrogen molecule dissociation certify the positive effects induced by doping, and the adsorption energy of CO2 has a linear relation with the transferred charges for all investigated catalysts which helps to explain the C‐O bond activation mechanism. Two pathways, Formate and Carboxyl, are investigated under same footing. It is noted that doping significantly reduces the hydrogenation barriers on two pathways compared with undoped surfaces. Moreover, the calculated TOF of formic acid formation is greatly increased on doped surfaces and Pt, Pd, Ru are identified as the most active dopants. In the end, it is concluded that reaction obeys Carboxyl mechanism and a valid descriptor of trans‐HCOOH* and H* formation energy is proposed for the screening of effective dopants.

Study of CO2 Adsorption Properties on the SrTiO3(001) Surface with Ambient Pressure XPS.

The adsorption properties of CO2 on the SrTiO3(001) surface were investigated using ambient pressure X-ray photoelectron spectroscopy under elevated pressure and temperature conditions. On the Nb-doped TiO2-enriched (1 × 1) SrTiO3 surface, CO2 adsorption, i.e., the formation of CO3 surface species, occurs first at the oxygen lattice site under 10-6 mbar CO2 at room temperature. The interaction of CO2 molecules with oxygen vacancies begins when the CO2 pressure increases to 0.25 mbar. The adsorbed CO3 species on the Nb-doped SrTiO3 surface increases continuously as the pressure increases but starts to leave the surface as the surface temperature increases, which occurs at approximately 373 K on the defect-free surface. On the undoped TiO2-enriched (1 × 1) SrTiO3 surface, CO2 adsorption also occurs first at the lattice oxygen sites. Both the doped and undoped SrTiO3 surfaces exhibit an enhancement of the CO3 species with the presence of oxygen vacancies, thus indicating the important role of oxygen vacancies in CO2 dissociation. When OH species are removed from the undoped SrTiO3 surface, the CO3 species begin to form under 10-6 mbar at 573 K, thus indicating the critical role of OH in preventing CO2 adsorption. The observed CO2 adsorption properties of the various SrTiO3 surfaces provide valuable information for designing SrTiO3-based CO2 catalysts.

Acceleration mechanisms of Fe and Mn doping on CO2 separation of CaCO3 in calcium looping thermochemical heat storage

The doping strategy with dark metallic oxide has proven effective in improving optical absorptions and heat storage performances of calcium-based materials for the direct solar-driven thermochemical energy storage system, but the microscopic mechanisms of accelerated decomposition of CaCO3 during heat storage process are still unclear. Carbide slag as an industrial waste with low cost and high CaO content is considered as a potential calcium-based precursor for large-scale thermochemical energy storage. Herein, the novel Fe-doped and Mn-doped calcium-based materials were synthesized from carbide slag and their optical absorption properties and heat storage performances were determined in the experiment. The optimum decomposition temperatures of CaCO3 during heat storage process decreased 10.5 °C and 18.6 °C due to Fe doping and Mn doping, respectively. The acceleration mechanisms by Fe doping and Mn doping for enhancing the CO2 separation of CaCO3 in the calcination stage of the heat storage process were investigated by density functional theory (DFT) calculations. The structural parameters, partial density of states, electron differential densities and energy barriers during CO32– dissociation in heat storage process on the doped CaCO3 and undoped CaCO3 surfaces were compared to clarify the effects of Fe doping and Mn doping on the CaCO3 decomposition. The energy barriers of Fe-doped material and Mn-doped material are 1.68 eV and 1.42 eV, respectively, which are 29.4% and 40.3% lower than that of undoped material. This work helps to understand the microscopic mechanisms of accelerated CaCO3 decomposition by Fe and Mn during heat storage process.

Effects of Alloying Element on Hydrogen Adsorption and Diffusion on α-Fe(110) Surfaces: First Principles Study

Based on first principles density functional theory (DFT) methods, this study employed the Cambridge Serial Total Energy Package (CASTEP) module within Materials Studio (MS) software under the generalized gradient approximation to investigate the adsorption, diffusion behavior, and electronic properties of hydrogen atoms on α-Fe(110) and α-Fe(110)-Me (Mn, Cr, Ni, Mo) surfaces, including calculations of their adsorption energies and density of states (DOS). The results demonstrated that doping with alloy atoms Me increased the physical adsorption energy of H2 molecules on the surface. Specifically, Mo doping elevated the adsorption energy from −1.00825 eV to −0.70226 eV, with the largest relative change being 30.35%. After doping with Me, the chemical adsorption energy of two hydrogen atoms does not change significantly, among which doping with Cr results in a decrease in the chemical adsorption energy. Building on this, further analysis of the chemical adsorption of single atoms on the surface was conducted. By comparing the adsorption energy and the bond length between a hydrogen atom and iron/dopant metal atom, it was found that Mo doping has the greatest impact, increasing the bond length by 58.58%. Analysis of the DOS functions under different doping conditions validated the interaction between different alloy elements and H atoms. Simultaneously, simulations were carried out on the energy barrier crossed by H atoms diffusing into the metal interior. The results indicate that Ni doping facilitates the diffusion of H atoms, while Cr, Mn, and Mo hinder their diffusion, with Mo having the most significant effect, where its barrier is 21.88 times that of the undoped surface. This conclusion offers deep insights into the impact of different doping elements on hydrogen adsorption and diffusion, aiding in the design of materials resistant to hydrogen embrittlement.

Tuning the adsorption of H2O, H2 and O2 molecules on diamond surfaces by B-doping

In this study, the fundamental interactions between the low Miller index (001), (110) and (111) B-doped diamond surfaces and H2O, H2 and O2 molecules, which are commonly present during growth, in ambient air and involved in electrochemical reactions, are investigated by means of ab initio simulations. The results are presented in close comparison with previous studies on undoped diamond surfaces to reveal the impact of B doping. It is demonstrated that the B dopant is preferably incorporated on the topmost carbon layer and enhances the adsorption of H2O by forming a dative bond with O. On the contrary in some cases, it seems to weaken the adsorption of O2, compared to the undoped diamond. Moreover, a noticeable displacement of the surface atoms attached to the fragment of the dissociated H2O and O2 molecules was observed, which can be associated to early stages of wear at the atomistic level. B doping was also found to reduce the energy barriers for water dissociation in most cases, with this effect being most pronounced in the C(111) surfaces. These qualitative and quantitative results aim to provide useful insights for the development of improved protective coatings and electrochemical devices.

Adsorption mechanism of formaldehyde, ammonia and sulfur dioxide gases on inexpensive metal-doped ZnO surface: A DFT study

Here, the adsorption mechanisms and detection performance of three different hazardous gases, including formaldehyde (CH2O), ammonia (NH3), and sulfur dioxide (SO2), on undoped ZnO and inexpensive metal-doped ZnO surfaces were studied by density functional theory (DFT). CH2O and NH3 are physically adsorbed on the zinc top site (t-site) and six-membered ring pore site (p-site) on the undoped ZnO surface, and the adsorption energies are -0.56 eV and -0.32 eV. The difference is that SO2 is weakly chemisorbed on bridge site (b-site) of ZnO surface with an adsorption energy of 1.78 eV. The adsorption energy of Al-doped ZnO for CH2O, NH3, and SO2 is higher than that of undoped ZnO, reaching -1.64 eV, -1.69 eV, and -3.62 eV respectively. The adsorption properties of Cu-doped ZnO for CH2O and SO2 are not significantly improved with exception of NH3. Collectively, the adsorption mechanism of undoped and doped ZnO or hazardous gases is elucidated, which provides theoretical guidance for the further utilization of ZnO substrate materials in the field of gas sensitivity.

Metal dopant infused superhydrophobic aluminum surface through sustainable processing

The present work proposes a simple, scalable, and economical route for producing superhydrophobic surfaces using thermomechanical and microwave-assisted hydrothermal treatments. Infusing dopants (Mg, Fe) during thermomechanical processing resulted in a distinct and denser nanostructures on aluminum surface. The silanization of these surfaces resulted in superhydrophobicity (θa > 160°) with low hysteresis (≈ 2°) and adhesion (≈ 25 µN) compared to un-doped surface. The reduction in pitch between nanostructures enhanced capillary pressure (> 900 kPa), stabilizing Cassie state and restricting three-phase line sagging. The present work highlights the importance of doping in enhancing the durability of nanostructures for improving de-wettability.

Theoretical Investigation of the Electrochemical Oxidation of H2 and CO Fuels on a Ruddlesden-Popper SrLaFeO4-δ Anode.

The electrochemical oxidation of H2 and CO fuels have been investigated on the Ruddlesden-Popper layered perovskite SrLaFeO4-δ (SLF) under anodic solid oxide fuel cell conditions using periodic density functional theory and microkinetic modeling techniques. Two distinct FeO2-plane-terminated surface models differing in terms of the underlying rock salt layer (SrO or LaO) are used to identify the active site and limiting factors for the electro-oxidation of H2, CO, and syngas fuels. Microkinetic modeling predicted an order of magnitude higher turnover frequency for the electro-oxidation of H2 compared to CO for SLF at short-circuit conditions. The surface model with an underlying SrO layer was found to be more active with respect to H2 oxidation than the LaO-based surface model. At an operating voltage of less than 0.7 V, surface H2O/CO2 formation was found to be the key rate-limiting step, and the surface H2O/CO2 desorption was the key charge transfer step. In contrast, the bulk oxygen migration process was found to affect the overall rate at high cell voltage conditions above 0.9 V. In the presence of syngas fuel, the overall electrochemical activity is derived mainly from H2 electro-oxidation and CO2 is chemically shifted to CO via the reverse water-gas shift reaction. Substitutional doping of a surface Fe atom with Co, Ni, and Mn revealed that the H2 electro-oxidation activity of FeO2-plane terminated anodes with an underlying LaO rock salt layer can be improved with dopant introduction, with Co yielding a three orders of magnitude higher activity relative to the undoped LaO surface model. Constrained ab initio thermodynamic analysis furthermore suggested that the SLF anodes are resistant toward sulfur poisoning both in the presence and absence of dopants. Our findings reflect the role of various elements in controlling the fuel oxidation activity of SLF anodes that could aid the development of new Ruddlesden-Popper phase materials for fuel cell applications.

Effect of transition metal on the structure and oxidation behavior of ZrB2 (0 0 0 1): Experimental and theoretical calculations

ZrB2 can withstand extreme environments, but the high-temperature oxidation prevented them from being applied as possible thermal protection system materials. The effect of transition metal (Tm = Ta, Hf, Mo, and W) on oxidation resistance of ZrB2 was systematically investigated by the first principles calculations, including ab initio molecular dynamics, and experimental tests. The results showed that the doped atoms, especially Hf atom, increased the adsorption energy of O atoms, which prohibited the O adsorb on the surface of ZrB2. Besides, the energy barrier of O atom migration on the Hf-doped surface and inward migration is 0.60 eV and 6.68 eV, which is higher than the un-doped surface. This showed that Hf performs well in inhibiting the diffusion of O. The reason was that the doped atoms increased the strength of B-Zr and O-Zr bonds, respectively. Finally, to verify the theoretical calculations, ZrB2 and (Zr, Tm) B2 solid solutions were prepared by using pressure-less sintering and the thermal gravimetric tests were carried out. The experimental results showed that the (Zr, Tm) B2 solid solutions have better oxidation resistance than ZrB2, which is consistent with the results from our theoretical calculations. In this work, the modification mechanism of doping atoms on the oxidation resistance of ZrB2 was explained from the point of view of adsorption and diffusion. And it provides guidance for promoting the application of ZrB2 at high temperature.

Effect on albumin and fibronectin adsorption of silver doping via ionic exchange of a silica-based bioactive glass

Protein adsorption is a crucial step in the life of biomaterials for bone application, such as bioactive glasses. The investigation of adsorption mechanisms is a difficult task per se, which is even more complex on bioactive glasses due to surface reactivity. Here, the effect of silver doping by ionic exchange on the interaction of a silica-based bioactive glass with albumin and fibronectin, serum proteins related to osseointegration, is reported. The presence of silver does not change relevant surface properties such as topography, surface energy, wettability, or surface ζ potential. Nevertheless, the interactions with proteins are much different. The presence of silver significantly increases the adsorption of albumin and fibronectin and leads to a higher loss of secondary structure compared to the undoped surface, as a consequence of the interactions and bonding between silver and thiols in the cysteine residues. Selectivity of silver-doped glass is discovered: Ag enhances more adsorption and denaturation of albumin since it has more cysteines than fibronectin. It is also here observed that due to the formation of a hydrated silica gel layer during adsorption, proteins are not only present on the surface of the bioactive glasses, but also embedded inside the surface reaction layer.

New insights into the effect of zirconium dopant on tritium release from Li2TiO3 (001) surface from first-principles calculation

The influence of zirconium (Zr) dopants on tritium release from Li2TiO3 (001) surface was researched by density functional theory (DFT) calculations. The energy barriers for T2 and T2O molecules formation on undoped and doped surfaces were calculated and compared by using climbing-image nudged elastic band (CI-NEB) method. It was found that T2O is more easily generated than T2 on the surfaces. And Zr dopants can significantly promote the production and release for T2O on the surface of Li2TiO3. Especially when Zr atoms doping ratio is to be 3.12 atom % (Zr3), the barrier of T2O formation changed from 0.97 eV on undoped surface to spontaneous formation on doped surface. The energy barrier for T2O desorption on the surface also decreases to a smaller energy barrier of about 0.42 eV. Although the catalytic effect of Zr doping on T2 formation on the surface is relatively weak. The electronic characteristics show that the doping of Zr atoms can influence the charge transfer of surface atoms, making OT group more likely to appeal to adjacent T atom, which may be the reason for promoting the formation of T2O by Zr dopants. This study can provide useful details for the effect mechanism and catalytic behavior of Zr dopants on the release of tritium from Li2TiO3 surface.

Boron-induced controlled synthesis of Co-nano particles over Bx(CN)y matrix for CO hydrogenation in aqueous media

Bx(CN)y supported cobalt nanoparticles have been synthesized by regulating the ratios of melamine and boric acid precursors. The carbonization step is adequate to generate the desired controlled-sized cobalt particles at an auto-reduced state that can eliminate the requirement of promotors (e.g., Pt) for the hydrogen-spillover effect. The presence of nitrogen in support enhances the dispersion of cobalt particles by providing sites for cobalt to nucleate and grow due to the interaction between cobalt and Π electrons from the sp2-N center. Boron in the catalyst system significantly stabilizes the catalyst, thus improving its lifetime. However, the excess of boron promotes the aggregation of cobalt particles; therefore, optimal boron loading is preferable. Moreover, the binding energy calculation of Co6 over the B-doped and undoped C3N4 surface computed through DFT studies shows a reduction in metal-support interaction with the addition of boron, which leads to the aggregation of the cobalt particles with high boron. Overall, the catalyst with the optimized boron and nitrogen-containing support-stabilized cobalt particles is highly efficient in the aqueous phase Fischer-Tropsch synthesis.

Modelling of Tungsten (C59W), Osmium (C59Os), and Platinum (C59Pt) Doped Fullerenes for Drug Delivery of Biguanides (BNG) and Metformin (MET): DFT Perspective

AbstractOwing to the vast range of exciting ideas and chances for the diagnosis and treatment of diabetes, the number of people with the disease has increased significantly in both developed and developing nations, with the greatest burden typically falling on indigenous people and socially disadvantaged groups. Nanostructures, however, have drawn a lot of interest because of their capacity to specifically target diabetes cells without damaging healthy cells. Herein, the potential of fullerene (C60) surface doped with C59Os, C59W, and C59Pt is explored as drug delivery systems for biguanides and metformin using density functional theory (DFT) computation at the M06‐2X/Gen/LanL2DZ/6‐311++G(d,p) level of theory. Interestingly, results obtained in this investigation specify that metformin interacts with both the doped and updoped surfaces more strongly than biguanides. Fascinatingly, the energy gap obtained from frontier molecular orbital (FMO) accounted for the significant reactivity and stability strength in the following order: MET@C59W>MET@C59Pt>MET@C59Os>MET@C60, whereas BGN@C59 W>BGN@C59Pt>BGN@C59Os>BGN@C60. Substantially, hydrogen bonding was found to be crucial in the interactions between the drug molecules and all doped and undoped surfaces through non‐covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM). Also worth mentioning is the complexes′ propensity for forward electron transfer, which is aided by their severe electronegative values, thus explicating that the doped surfaces are a preferable carrier for both metformin and biguanides. Although, theoretically, it follows that doped surfaces are promising drug delivery targets most notably for metformin.

Alkali metal (Na and Li) doped C18 nanocluster with boosted electronic and nonlinear optical properties

To expand the uses of material in nonlinear optics, strategies for producing extraordinary nonlinear optical materials with excess electron compounds are widely known in the literature. In this study, cyclo18 (C18) nanocluster was doped with alkali metals (Na and Li) in such a way that the metal atom was placed inside the C18 surface to explore their nonlinear optical (NLO) properties by density functional theory (DFT) calculations. Alkali metals doping has lowered the band gap energy (4.64–4.55) when compared to the pure surface (6.76 eV). The alkali metals possess loosely bound excess electrons which can be easily excited, hence lowering the doped systems excitation energies, resulting a remarkable increase in the hyperpolarizabilities. The highest value of hyperpolarizability (17,975.051 C3 m3 J-2) has been explored by C18-Na. Moreover, isotropic and anisotropic polarizabilities (αiso and αaniso) were also computed for the alkali doped systems and outstanding outcomes were observed (αiso ranges from 45.69 to 53.07 C3 m3 J-2) and (αaniso ranges 49.91–61.07 C3 m3 J-2), when comparison was made between the doped and undoped surfaces. NCI analysis show that there exist van der Waals interactions among surface and the dopant. Absorption analyses were performed, and the results showed that these doped complexes having excess electrons absorbs at higher wavelength ranging from 675 to 683 nm. Furthermore, FMOs, TDM and NBO analysis revealed the outstanding electronic and charge transfer properties of these doped systems. As a result of our findings, alkali metal doped C18 may be a contender for efficient nonlinear optical characteristics

Adsorption of NH3 and NO2 Molecules on Sn-Doped and Undoped ZnO (101) Surfaces Using Density Functional Theory

The adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH3 and NO2 molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using density functional theory. The current findings revealed that both molecules adsorb via chemisorption rather than physisorption, with all the adsorption energy values found to be negative. The calculated adsorption energy revealed that the adsorption of the NH3 molecule on the bare ZnO surface is more energetically favorable than the adsorption of the NO2 molecule. However, a stable adsorption configuration was discovered for the NO2 molecule on the surface of the Sn-doped ZnO surface. Furthermore, the adsorption on the undoped surface increased the work function, while the adsorption on the doped surface decreased. The charge density redistribution showed charge accumulation and depletion on both adsorbent and adsorbate. In addition, the density of states and band structures were studied to investigate the electronic behavior of NH3 and NO2 molecules adsorbed on undoped and Sn-doped ZnO (101) surfaces.

Properties of topological crystalline insulator Pb0.5Sn0.5Te epitaxial films doped with bismuth

We report here on the properties of topological crystalline insulator Pb0.5Sn0.5Te epitaxial films doped with bismuth at levels from 0% (undoped) to 0.15%. The undoped film exhibits a p-type character due to metal vacancies. As the doping level rises, the hole concentration reduces. At a level of 0.06%, the electrical character inverts to n-type and the electron density continues to increase for rising doping level up to 0.15%. This result demonstrates an effective extrinsic n-type doping of Pb0.5Sn0.5Te crystal with bismuth due to substitutional Bi atoms in metal sites. High-resolution x-ray diffraction and reciprocal space mapping show that fully relaxed high-quality films are obtained. A pristine (111) film surface is revealed after removal of the Te cover layer using a method combining Ar+ sputtering and thermal desorption. Angle-resolved photoemission spectroscopy (ARPES) data acquired at 30 K near the Γ¯ point of the undoped film surface show a parabolic-like dispersion of the bulk valence band close to the Fermi level. Now, the ARPES data for a sample doped with 0.1% of Bi reveal that the chemical potential is shifted by 40 meV upwards in the direction of the conduction band. The ARPES results also indicate that there might be a discrepancy between surface and bulk chemical potential in the doped sample. This divergence suggests that Te atoms diffuse into the surface during the thermal process to desorb the protective layer, inverting the surface to p-type.

Hydrogen production via steam reforming of glycerol over Ce-La-Cu-O ternary oxide catalyst: An experimental and DFT study

In this study, Ce-La-xCu-O catalysts with distinct Cu contents were fabricated through two different microwave methods; conventional microwave (MW) method and enhanced microwave method, where air cooling (AC) during heating was applied and studied for glycerol steam reforming. The characterization of catalysts reveals that the synthesis methods (MW and AC) influence mainly on the degree of Cu incorporation into the Ce-La-O fluorite lattice, thus leading to one or two phases system. In glycerol steam reforming, MW catalysts showed improvement in glycerol conversion (X) and glycerol conversion to gaseous products (Xgas) with an increase of temperature from 400 to 750 °C; a higher tradeoff between total conversion X (93–94%) and Xgas (89–93%) was attained at 750 °C. The H2 yield over MW catalysts was attained in the range of 3.8–5.0 mol/mole of glycerol. Interestingly, Ce-La-10Cu-O (AC) catalyst exhibits higher glycerol conversion, conversion to gaseous products and higher yield of H2 (5.3 mol/mole of glycerol) as compared to MW catalyst. Moreover, the Ce-La-10Cu-O (AC) catalyst exhibited high stability and deactivated at slower rate. The improved performance of AC catalyst can correlate to a more homogeneous Cu incorporation into Ce-La-O mixed oxide thus forming more accessible active sites to reactants which overall impact on the catalytic performance. DFT calculations showed that doping ceria (111) surface greatly facilitates the adsorption of glycerol compared to the undoped ceria surface by tuning the adsorption energy and the surface-glycerol distance, to −1.42 eV and 1.09 Å, respectively, and by shifting the Fermi level into the valence band (p-type doping), enhancing with the latter the glycerol chemisorption.

Impact of surface doping profile and passivation layers on surface-related degradation in silicon PERC solar cells

Illuminated solar cells are susceptible to various degradation mechanisms that can act to reduce the total energy yield when deployed. One potentially severe form is an increase in carrier recombination in the surface regions. This effect has been reported at both the undoped rear surface and phosphorous diffused emitter of PERC solar cells. This work investigates the influence of a range of surface conditions on the surface-related degradation (SRD) behaviour in PERC solar cells. It is shown that SRD is strongly affected by the doping profile of phosphorous emitters, the use of thin thermal oxides with SiN x :H dielectric passivation layers, the substrate material, and the configuration of the rear surface passivation. It finds that more lightly doped emitters result in more front side SRD, with its extent increasing with the introduction of the SiO 2 /SiN x :H surface passivation layers. Czochralski silicon (Cz-Si) wafers were observed to be significantly more susceptible to surface degradation than multi-crystalline silicon (mc-Si) wafers, which we attribute to less trapping of hydrogen in the bulk of those substrates. On the rear side of PERC cells, surface degradation was only observed in structures that incorporated the combination of SiO 2 /SiN x :H rear layers. No SRD was observed in the existing Al 2 O 3 /SiN x :H technology used in the industrial PERC cells studied. However, the results presented have implications for future commercial solar cell technologies, which are transitioning towards lightly doped emitters and commonly incorporate thermal oxides for surface passivation. • The introduction of more lightly doped emitters leads to severe SRD, with its extent increasing with the introduction of theSiO 2 . • Cz-Si wafers were observed to be substantially more susceptible to surface degradation than mc-Si wafers. • Rear side SRD was only observed in PERC precursors that incorporated the combination of SiO 2 /SiN x :H rear layers.

A comparison of in vitro cytotoxicity of undoped and doped surface modified CaS nanoparticles

In the present study we compare the cytotoxicity of undoped and doped surface modified CaS nanoparticles synthesized by wet chemical co-precipitation technique using L929 human fibroblasts cell lines. The toxicity was determined by evaluating the cell viability and changes in cell morphology. In addition, the half-maximal inhibitory concentration (IC50) values for all the samples were also compared. This analysis shows that undoped and terbium doped TEOA capped CaS nanoparticles are more biocompatible and will be better candidates for various applications in the biomedical field.

Interaction between HCHO molecule and B, Zn co-doped g-C3N4 surface: A DFT study

The interaction between formaldehyde (HCHO) and B, Zn co-doped g-C3N4 surface was studied using density functional theory calculation. Compared with previous study for HCHO adsorption on un-doped surface, it was found that the doping of B, Zn increases the active sites of HCHO degradation in g-C3N4 surface, which changes from one of un-doped surface to three of doped surface. In these three adsorption configurations, the interactions between HCHO and B, Zn co-doped g-C3N4 surface are all very strong, which leads to the dramatic change of doped surface structure. Therefore, the calculated adsorption energies of three configurations (MA,-1.159eV; MB, -1.084eV; MC, -0.898 eV) are much larger than that of HCHO on the surface of pure g-C3N4 (-0.213 eV). HCHO molecules are dissociated in all three models with the break of two C–H bonds. The two broken hydrogen atoms are bonded to two nitrogen atoms of the surface to form H–N bonds, respectively. The charge transfers from HCHO molecules to B, Zn co-doped g-C3N4 surface in three systems (MA, 0.347 e; MB, 0.562 e; MC, 0.489 e), and the hydrogen and oxygen atoms of HCHO are electron donors, while doping atoms (B and Zn) of surface are major acceptors.