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The schematic diagram of different Sn-5s and I-5p antibonding strengths of FASnI3 and MASnI3 due to various bond lengths of Sn–I.

The use of rare-earth (RE) (e.g., Eu2+/Ce3+) ions as single luminescent centers in phosphors with tailorable emission properties has been extensively studied for their potential use in white LEDs. However, significant limitations remain, in particular, for red-emitting phosphors due to the inherently broad excitation bands which result from the underlying d–f transitions and span large parts of the visible spectral region. Guided by density functional theory calculations on the ligand structure of the non-RE Bi3+ ion, we report here on an alternative class of phosphors, [(Y,Sc)­(Nb,V)­O4:Bi3+], which exhibit homogeneous Bi3+ luminescence. In these materials, adjustment of the cation fractions enables dedicated tailoring of the excitation scheme within the spectral range of ∼340–420 nm and, in the meanwhile, allows for tunable emission spanning from about 450 nm (blue) to 647 nm (orange-red). The practical absence of any overlap between the emission and excitation spectra addresses the issues of emission color purity and visible reabsorption. Tailoring through band-gap modulation is achieved by single or parallel substitution of Nb by V and Y by Sc. Such topochemical design of the ligand configuration enables modulation of the electronic band gap and thus provides a new path toward tunable phosphors, exemplarily based on Bi3+ single doping.

We report on a red-emitting ScVO4:Bi3+ phosphor which does not show excitation at energies below 2.88 eV (430 nm). X-ray diffraction, time-resolved, and quantitative photoluminescence (PL) spectroscopy were employed to characterize relations between crystal structure and luminescence properties of the material. Results show that incorporation of Bi3+ renders the blue photoemission of blank ScVO4 to red. Dynamic luminescence analysis between 10 and 300 K reveals a complicated dependence of energy transfer from VO4 3– groups to Bi3+ ions and population redistribution of 3P1 and 3P0 of Bi3+ on temperature. This reflects in distinct changes in the luminescence decay functions. That is, a dramatic decrease of Bi3+ luminescence lifetime occurs from hundreds to only several microseconds. Density functional theory is employed to reveal how the unusual red Bi3+ luminescence comes, and results indicate that the perturbation of oxygen vacancies which is generated readily when bismuth precipitates into ScVO4 is the reason for the experimental observation, although the vacancies themselves do not show photoluminescence. Upon excitations at 330 and 380 nm, internal quantum efficiencies can be up to ∼56% and ∼47%, respectively, implying the potential application of the red phosphor in warm-white-light-emitting diodes. As a proof of concept, an exemplary device was developed by combining the present phosphor with an ultraviolet-light-emitting diode and a commercial phosphor (Ba, Eu)MgAl10O17:Mn. We obtain a color rendering index (CRI) of >90 and a color temperature of ∼4306 K at chromaticity (0.3744, 0.3991).

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We report a novel kind of oxidized silicon nanospheres (O-SiNSs), which simultaneously possess excellent aqueous dispersibility, high photoluminescent quantum yield (PLQY), ultra photostability, wide pH stability, and favorable biocompatibility. Significantly, the PLQY of the O-SiNSs is as high as 25%, and is stable under intense UV irradiation and in acidic-to-basic environments covering the pH range 2-12. To our best knowledge, it is the first example of water-dispersed silicon nanoparticles which possess both high PLQY and robust pH stability suitable for broad utility in bioapplications. Furthermore, the O-SiNSs are readily conjugated with antibody, and the resultant O-SiNSs/antibody bioconjugates are successfully applied in immunofluorescent cell imaging. The results show that the highly luminescent and stable O-SiNSs/antibody bioconjugates are promising fluorescent probes for wide-ranging bioapplications, such as long-term and real-time cellular labeling.

Zhao et al. Reply In the first sentence of the Comment [1], the authors refer to four systems: GaNð10 10Þ-1H, ZnOð10 10Þ-1H, GaNð10 10Þ-Li, and ZnOð10 10Þ-1Li. In the second sentence, the authors claim to demonstrate that "a charge-density-wave (CDW) phase is due to the artifact of the generalized gradient approximation (GGA), while the antiferromagnetic (AFM) ground state is predicted by the hybrid DFT calculation…" The Comment contains a single table, showing the total energy of the GaNð10 10Þ-1H system only. No numerical results were presented for the other three systems. It is not clear how the authors arrived at their very general conclusion.We have checked the validity of Kim et al.'s claim by performing new calculations using two popular hybrid functionals, HSE06 [2,3] and B3LYP [4], on the four systems mentioned in the Comment. These two hybrid functional methods are generally considered to be at the same level of accuracy. All hybrid functional calculations are performed on a 12-layer slab separated by a 12 Å vacuum. The two-dimensional k grid of the Brillouin zone is 8 × 6 for the pð1 × 1Þ cell and the same density is used for larger cells. The results are listed below.Based on these results, we draw a few observations: (i) For the GaNð10 10Þ-1H system, different hybrid functionals produce different ground states. The conclusions are not consistent. Our Table I shows that the B3LYP hybrid method favors the CDW state by 0.21 eV per pð2 × 2Þ unit cell, and that this preference is reversed with the HSE06 hybrid method, which instead favors the AFM state by 0.06 eV. This is similar to Kim's HSE results, which also favored the AFM state by 0.07 eV. Importantly, Kim et al. also perform RPA calculations, which favor the AFM state by 122 meV per pð2 × 2Þ unit cell in GaN-1H. We have confirmed this value for RPA. For the GaNð10 10Þ-1Li system, however, both hybrid functionals B3LYP and HSE06 favor the CDW ground state, by 0.5 and 0.25 eV, respectively. For GaNð10 10Þ-1Li, we have also carried out RPA calculations [5-8] using a four-layer slab. The RPA results favor the CDW state over the AFM state by 0.16 eV. Thus, for GaNð10 10Þ-1Li, all results using B3LYP, HSE06 and RPA support our findings [9], and disagree with the claim of Kim et al. (ii) For ZnOð10 10Þ with 1H and 1Li, both HSE06 and B3LYP functionals favor the CDW ground state, according to our new results shown

Density functional theory (DFT) calculations are employed to study H 2 O and CO dissociations on a set of CuNi bimetallic surfaces aiming at exploring the optimal Ni ensemble on Cu(111) for an efficient waterÀgas shift (WGS) process, i.e., splitting H 2 O with high reactivity and avoiding CO activation. We found that Ni additives in the Cu(111) surface layer including a Ni monomer can remarkably enhance water splitting. Meanwhile, H 2 O dissociation barriers (E act ) are strongly correlated with the H adsorption energies (E ad ): the larger E ad , the smaller E act . Moreover, H 2 O dissociation may be more practical via the dissociated H* rather than OH closing to Ni atoms. For the scission of the CÀO bond, the process is unfavorable on Ni monomers, though it is obviously promoted on Ni dimers, trimers, and other ensembles with higher Ni content. It is deduced that the selectivity of the CuÀNi bimetallic catalysts toward WGS would decrease with increasing Ni concentration. These findings suggest that the bimetallic CuNi catalysts with highly dispersed Ni ensembles containing lower Ni concentration should exhibit high performance for the WGS process.