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We report the unprecedented synthesis of one-handed helical spiro-conjugated ladder polymers with well-defined primary and secondary structures, in which the spiro-linkeddibenzo[a,h]anthracene fluorophores are arranged in a one-handed twisting direction, through quantitative and chemoselective acidpromoted intramolecular cyclizations of random-coil precursor polymers composed of chiral 1,1’-spirobiindane and achiral bis[2-(4-alkoxyphenyl)ethynyl]phenylene units. Intense circular dichroism (CD) and circularly polarized luminescence (CPL) were observed, whereas the precursor polymers exhibited negligible CD and CPL activities. The introduction of 2,6-dimethyl substituents on the 4- alkoxyphenylethynyl pendants is of key importance for this simple,quantitative, and chemoselective cyclization. This strategy is applicable to the defect-free precise synthesis of other varieties of fully p-conjugated molecules and coplanar ladder polymers that have not been achieved before.

Herein, we report the design of novel ultraviolet luminescent CsPbCl3 nanocrystals (NCs) with the emission peak at 381 nm through doping of cadmium ions. Subsequently, a surface passivation strategy with CdCl2 is adopted to improve their photoluminescence quantum yield (PLQY) with the maximum value of 60.5 %, which is 67 times higher than that of the pristine counterparts. The PLQY of the surface passivated NCs remains over 50 % after one week while the pristine NCs show negligible emission. By virtue of density functional theory calculations, we reveal that the higher PLQY and better stability after surface passivation may result from the significant elimination of surface chloride vacancy (VCl ) defects. These findings provide fundamental insights into the optical manipulation of metal ion-doped CsPbCl3 NCs.

The synthesis of hydrophilic lanthanide-doped nanocrystals (Ln3+ -NCs) with molecular recognition ability for bioimaging currently remains a challenge. Herein, we present an effective strategy to circumvent this bottleneck by encapsulating Ln3+ -NCs in graphene oxide (NCs@GO). Monodisperse NCs@GO was prepared by optimizing GO size and core-shell structure of NaYF4 :Yb,Er@NaYF4 , thus combining the intense visible/near-infrared II (NIR-II) luminescence of NCs and the unique surface properties and biomedical functions of GO. Such nanostructures not only feature broad solvent dispersibility, efficient cell uptake, and excellent biocompatibility but also enable further modifications with various agents such as DNA, proteins, or nanoparticles without tedious procedures. Moreover, we demonstrate in proof-of-concept experiments that NCs@GO can realize simultaneous intracellular tracking and microRNA-21 visualization, as well as highly sensitive in vivo tumor-targeted NIR-II imaging at 1525 nm.

Lanthanide (Ln3+ )-doped luminescent nanoparticles (NPs) with emission in the second near-infrared (NIR-II) biological window have shown great promise but their applications are currently limited by the low absorption efficiency of Ln3+ owing to the parity-forbidden 4f→4f electronic transition. Herein, we developed a strategy for the controlled synthesis of a new class of NIR-II luminescent nanoprobes based on Ce3+ /Er3+ and Ce3+ /Nd3+ co-doped CaS NPs, which can be effectively excited by using a low-cost blue light-emitting diode chip. Through sensitization by the allowed 4f→5d transition of Ce3+ , intense NIR-II luminescence from Er3+ and Nd3+ with quantum yields of 9.3 % and 7.7 % was achieved, respectively. By coating them with a layer of amphiphilic phospholipids, these NPs exhibit excellent stability in water and can be exploited as sensitive NIR-II luminescent nanoprobes for the accurate detection of an important disease biomarker, xanthine, with a detection limit of 32.0 nm.

Applications of persistent luminescence phosphors as night or dark-light vision materials in many technological fields have fueled up a growing demand for rational control over the emission profiles of the phosphors. This, however, remains a daunting challenge. Now a unique strategy is reported to fine-tune the persistent luminescence by using all-inorganic CsPbX3 (X=Cl, Br, and I) perovskite quantum dots (PeQDs) as efficient light-conversion materials. Full-spectrum persistent luminescence with wavelengths covering the entire visible spectral region is achieved through tailoring of the PeQD band gap, in parallel with narrow bandwidth of PeQDs and highly synchronized afterglow decay owing to the single energy storage source. These findings break through the limitations of traditional afterglow phosphors, thereby opening up opportunities for persistent luminescence materials for applications such as a white-emitting persistent light source and dark-light multicolor displays.

A series of dibenzo[a,f][1,3,5]triazino[2,1,6-cd] pyrrolizine compounds have been synthesized from phthalonitriles by a facile intramolecular cyclization process using "half-phthalocyanine" precursors, and they were characterized by X-ray crystallography, 1 H NMR spectroscopy, UV/Vis, and theoretical calculations. These compounds have spectroscopic profiles similar to phthalocyanines and porphyrins, although their inner-core structures and coordination types are totally different. They can be regarded as a new class of aromatic fused-ring compounds. The low-energy absorption of these new fused-ring compounds are located at around 600 nm. Such a low-energy π-π* transition is scarce in aromatic compounds having a similar molecular size. According to the nomenclature of phthalocyanines, these types of compounds have been named phthalorubines (Prs).

G-quadruplexes are implicated in important cellular processes. Previous studies mostly focused on intramolecular G-quadruplexes of three or more G-quartets. Those composed of two G-quartets were only shown to form in single-stranded oligonucleotides. On the basis of electrophoresis, DMS footprinting, fluorescence labeling, and photo-cross-linking, we detected the formation of DNA:RNA hybrid G-quadruplexes (HQs) of two G-quartets during the transcription of DNA duplexes. These HQs have a lifetime on the minute scale and are stabilized by a stabilizing ligand. They are far shorter-lived than the HQs of three G-quartets, which last for hours. The occurrence of putative formation motifs of such HQs shows a transcription-dependent strand-biased selection, thus supporting their formation and function in genomes. They are present in almost all human genes in large amounts. We speculate that the two-G-quartet HQs may be a distinct type of G-quadruplexes that may play a role in timely responsive processes and for purposes of fine-tuning.

Karbowiak et al. recently commented on our Communication “Breakdown of Crystallographic Site Symmetry in Lanthanide-Doped NaYF4 Crystals”. [1] They attempted to criticize the crystal-field (CF) analysis of Eu in disordered NaYF4 based on their surmise. Unfortunately, there are numerous misunderstandings in their correspondence. In this reply, we respond to their comment and clarify our interpretations of the issues they raised. Regarding the adoption of the CF parameters (CFPs) of Eu in Gd2O3 as the starting values in the fit, it is true that the coordination environments of Gd2O3 and NaYF4 host are somewhat different. However, it should be pointed out that both aand b-NaYF4 are disordered crystals, where the site symmetry of Y isOh and C3h, respectively. [3] Once Eu ions are doped into such disordered crystals to substitute for Y, the symmetry of spectroscopic sites of Eu may differ drastically from that of crystallographic sites of Y, which is due to the mismatch of ionic radius between Eu and Y. The local site symmetry of Eu in NaYF4 can be revealed by the high-resolution emission spectra (Figure 1), selective excitation spectra, and photoluminescence (PL) decays at low temperature (Supporting Information, Figure S1). Note that our emission pattern of b-NaYF4:Eu 3+ is consistent with that reported by other groups. For instance, the line positions and splittings reported by Jia et al. are nearly identical to our results (Figure 1). In the PL pattern, the most crucial fingerprint to corroborate the low site symmetry in NaYF4:Eu 3+ crystals is the appearance of the D0!F0 peak. Furthermore, three and five CF transition lines of D0 to F1 and F2 were observed, which demonstrated the highest site symmetry of Eu in b-NaYF4, distorted from C3h, should be Cs. Such breakdown of crystallographic site symmetry in Eu-doped NaYF4 crystals was not only corroborated by these PL spectra, but also confirmed by the CF level fitting. To the best of our knowledge, until now no data on the CFPs of NaYF4 or other disordered crystals with similar structure and local site symmetry are available. The choice of the set of CFPs values of Gd2O3 as the starting ones in the fit is technically feasible based on the following considerations. First, as mentioned in Ref. [1], the highest spectroscopic site symmetries of Eu are found to descend from crystallographic Oh to Cs (or C2) in a-NaYF4, and from crystallographic C3h to Cs in b-NaYF4, respectively. Similar to the wellestablished CFP fitting strategy in this field, to rationally reduce the number of freely varied CFPs in the fit, we performed the energy level fitting by reasonably assuming the highest site symmetry of Cs for both aand b-NaYF4 in view of the same set of allowed CFPs for the site symmetry of Cs or C2. [7] Second, by using the CFPs of Gd2O3:Eu 3+ as starting values, the energy-level fitting yielded a relatively small root-mean-square deviations for aand b-NaYF4, namely, 13.5 and 13.8 cm 1 (with energy shifts in a range of 0–30 cm 1 for most of the levels), respectively, an important indicator for the goodness of the fit. Note that total 48 CF levels of Eu in a-NaYF4, instead of 41 levels as they criticized in their comment, were included in our fit. Figure 1. 10 K PL emission spectra of b-NaYF4:Eu 3+ reported in Ref. [5a] (upper) and our original work (lower), respectively. The CF transition line from D0 to F0 is marked by an asterisk.