Revealing the local atomic structure of doped halide perovskite quantum dots (QDs) is crucial for understanding how metal-ion incorporation tunes their optoelectronic properties. In particular, dopant-lattice interactions in CsPbI3 are governed by short-range distortions and dynamic lattice fluctuations that cannot be resolved by conventional diffraction methods. Here, we present a systematic investigation of Zn-doped CsPbI3 QDs over a wide Zn : Pb ratio (0-1.5) by combining optical spectroscopy with extended X-ray absorption fine structure (EXAFS) and X-ray total scattering analyses. An optimal Pb : Zn ratio of 1 : 1.25 yields a markedly enhanced photoluminescence quantum yield of up to 97%, accompanied by shortened carrier lifetimes, whereas excessive Zn doping deteriorates the optical performance. EXAFS reveals shortened Pb-I bond lengths, a general increase in coordination numbers, and reduced local octahedral distortion in Zn-doped samples compared with pristine CsPbI3 QDs. Complementary pair distribution function (PDF) analysis demonstrates PbI6 octahedral tilting and decreased atomic displacement parameters, indicating stabilisation of lattice fluctuations. These structural modifications collectively weaken electron-phonon coupling and suppress non-radiative recombination pathways, thereby accounting for the enhanced emission efficiency. This work establishes a direct correlation between dopant-induced local structural stabilisation and optoelectronic performance in CsPbI3 QDs.

Benzoyl peroxide (BPO) is widely used in polymer manufacturing, food processing and pharmaceutical products. However, its extensive application has raised significant safety concerns, including potential explosiveness, acute toxicity to aquatic organisms and carcinogenic risks, thereby increasing the demand for portable detection and accurate quantification methods. Herein, we report a ratiometric fluorescent probe based on PFBT/PFO-DBT polymer dots (Pdots), which exhibit strong red fluorescence owing to efficient fluorescence resonance energy transfer (FRET) from PFBT to PFO-DBT within the Pdots. Upon exposure to BPO, benzoyloxy radicals generated from BPO in the presence of Pdots selectively accept electrons from the excited PFBT donor, triggering a photoinduced electron transfer (PET) process that suppresses FRET and induces a pronounced ratiometric fluorescence response. The coupled FRET-PET regulation enables sensitive BPO quantification with a low limit of detection of 8.5 nM, excellent selectivity and anti-interference capability, as well as satisfactory recoveries and good agreement with high-performance liquid chromatography (HPLC) results. Furthermore, integration of the Pdots into sodium alginate hydrogel microspheres affords a portable sensing platform that is compatible with smartphone-based colorimetric analysis. This work establishes a novel design strategy based on regulated energy and charge transfer in semiconducting polymer nanomaterials for portable and reliable BPO sensing.

Graphitic carbon nitride (g-C3N4) is a promising photocatalyst for environmental remediation and energy conversion. In this work, we systematically explored the effects of high pressure and high temperature (HPHT) treatments on the structural and photocatalytic properties of g-C3N4. The material was sintered in a large cavity piston-cylinder press at 600 degrees C under pressures up to 3 GPa, and its photocatalytic activity was evaluated via Rhodamine B (RhB) degradation. Synchrotron X-ray total scattering and pair distribution function (PDF) analysis were employed to probe local structural changes, while X-ray photoelectron spectroscopy (XPS) was used to monitor the N2C/N3C ratio and the formation of carbon vacancies. High-pressure treatment alone led to reduced carbon content, increased N2C/N3C ratios, the generation of vacancy defects, and enhanced photocatalytic efficiency. At constant pressure, increasing temperature further promoted nitrogen loss and defect formation. X-ray total scattering and pair distribution function (PDF) analysis showed that pressure introduced mild long-range disorder, which was largely reversible upon heating. However, combined HPHT treatment induced broader PDF peaks and disrupted interlayer correlations, indicating enhanced stacking disorder. These results demonstrate that controlled HPHT processing enables precise tuning of the atomic structure and photocatalytic performance of g-C3N4, offering a strategy for advanced photocatalyst design.

It is important to image tumor micrometastases in fluorescence-guided surgery (FGS), which requires highly emissive materials with a high signal-to-background ratio. As one type of bright NIR-II dye, donor-acceptor-donor (D-A-D) molecules have been widely applied for in vivo imaging. However, the brightness of D-A-D molecules when encapsulated in nanoparticles for bioimaging is often unsatisfactory due to aggregation-caused quenching or a decrease in absorption. In this study, we introduced carbazole groups in the D-A-D molecules, which resulted in a reduction of fluorescence quenching in the aggregated state due to the larger intermolecular distance. Through proper engineering of the carbazole groups, the emission spectra of the nanoparticles could be red-shifted with a peak beyond 1000 nm, while maintaining strong absorption and high quantum yield. The brightest TBTC-4 nanoparticles were successfully applied for tumor micrometastasis imaging in mice, with metastases as small as 0.5 mm diameter, which demonstrates their promising clinical application in FGS.

Correction for ‘Local structure and lithium-ion diffusion pathway of cubic Li 7 La 3 Zr 2 O 12 studied by total scattering and the Reverse Monte Carlo method’ by Haolai Tian et al. , J. Mater. Chem. A , 2023, 11 , 25516–25533, https://doi.org/10.1039/D3TA04495E.

Metal-organic framework (MOF) glasses are an emerging class of glasses which complement traditional inorganic, organic and metallic counterparts due to their hybrid nature. Although a few zeolitic imidazolate frameworks have been made into glasses, how to melt and quench the largest subclass of MOFs, metal carboxylate frameworks, into glasses remains challenging. Here, we develop a strategy by grafting the zwitterions on the carboxylate ligands and incorporating organic acids in the framework channels to enable the glass formation. The charge delocalization of zwitterion-acid subsystem and the densely filled channels facilitate the coordination bonding mismatch and thus reduce the melting temperature. Following melt-quenching realizes the glass formation of a family of carboxylate MOFs (UiO-67, UiO-68 and DUT-5), which are usually believed to be un-meltable. Our work opens up an avenue for melt-quenching porous molecular solids into glasses.

In order to improve the fluorescence quantum yield (QY) of NIR-II-emitting nanoparticles, D-A-D fluorophores are typically linked to intramolecular rotatable units to reduce aggregation-induced quenching. However, incorporating such units often leads to a twisted molecular backbone, which affects the coupling within the D-A-D unit and, as a result, lowers the absorption. Here, we overcome this limitation by cross-linking the NIR-II fluorophores to form a 2D polymer network, which simultaneously achieves a high QY by well-controlled fluorophore separation and strong absorption by restricting intramolecular distortion. Using the strategy, we developed polymer dots with the highest NIR-II single-particle brightness among reported D-A-D-based nanoparticles and applied them for imaging of hindlimb vasculatures and tumors as well as fluorescence-guided tumor resection. The high brightness of the polymer dots offered exceptional image quality and excellent surgical results, showing a promising performance for these applications.

The cubic phase of Li 7 La 3 Zr 2 O 12 shows fast diffusion of the lithium ions. Combining total scattering measurements analysed by the RMC method with molecular dynamics simulations gives a detailed picture of the distribution of the Li + ions.

We report results from a study of the crystal and magnetic structures of strontium-doped BiFeO3using neutron powder diffraction and the Rietveld method. Measurements were obtained over a wide range of temperatures from 300-800 K for compositions between 10%-16% replacement of bismuth by strontium. The results show a clear variation of the two main structural deformations-symmetry-breaking rotations of the FeO6octahedra and polar ionic displacements that give ferroelectricity-with chemical composition, but relatively little variation with temperature. On the other hand, the antiferromagnetic order shows a variation with temperature and a second-order phase transition consistent with the classical Heisenberg model. There is, however, very little variation in the behaviour of the antiferromagnetism with chemical composition, and hence with the degree of the structural symmetry-breaking distortions. We therefore conclude that there is no significant coupling between antiferromagnetism and ferroelectricity in Sr-doped BiFeO3and, by extension, in pure BiFeO3.

We use in situ high-pressure neutron powder diffraction to study elastic properties of Fe3O4 magnetite nanoparticles of different sizes. It is found that nanoparticles are elastically softer than the bulk. Apart from the smallest nanoparticle of diameter 8 nm, the atomic and magnetic structures do not change significantly with nanoparticle size or pressure. The 8 nm sample appears to take a disordered spinel structure instead of the inverse spinel structure of the bulk and larger nanoparticles, as seen in bond lengths and magnetic structures. Synchrotron x-ray total scattering was used to support this interpretation. Furthermore, this study suggests that the influence of magnetic disorder at the nanoparticle surface is significant for the size of 8 nm.

A numerical simulation method was used in this study to explore the effects of equivalence ratio, intake air temperature, intake air pressure, compression ratio, and engine speed on the combustion and performance characteristics of cyclohexane/n-heptane dual-fuel HCCI (homogeneously charged compression ignition) using a zero-dimensional single-zone combustion model. In this paper, the ignition delay time and laminar flame speed were used to verify the selected chemical reaction kinetics mechanism, and the effect of each engine parameter variation on the combustion performance of cyclohexane/n-heptane dual-fuel HCCI was numerically simulated. The results demonstrate that the advanced combustion phase occurred with an increase in equivalence ratio, intake air temperature, intake pressure, and compression ratio as well as a decrease in engine speed. The work indicated increases on average by about 27% for each 0.2 increment in equivalence ratio. The excessive rise in intake air temperature leads to higher pressure rise rate and lower indicated work. For every 10 kPa improvement in intake pressure, the starting point of combustion is advanced by about 1.3 degrees CA, and the peak pressure in the cylinder is improved by about 11 bar. The appropriate improvement of the compression ratio increases the heat release rate and the indicated work. The effect of engine speed is not so significant. The peak in-cylinder pressure rises by only about 1.22 bar for each 100 rpm increment in engine speed, and the indicated work and indicated mean effective pressure improve only about 3%. Ultimately, it is found that the introduction of cyclohexane makes the low-temperature heat release region in HCCI combustion of cyclohexane/n-heptane weaker than that of pure heptane.

The near-zero thermal expansion of A2O(PO4)2 oxides (A = Th, U, Zr, and Hf) is investigated by first-principles calculations, and the role of structural flexibility, strongly related to transverse vibrations, is clarified. The results of lattice dynamics simulations indicate that the low positive or negative thermal expansion of A2O(PO4)2 mainly originates from the competition between phonon modes with positive and negative Gru''neisen parameters in the low-frequency range. This work provides new insights to help the discovery and design of new materials with ultralow or controlled thermal expansion.

Magic-size clusters are ultra-small colloidal semiconductor systems that are intensively studied due to their monodisperse nature and sharp UV-vis absorption peak compared with regular quantum dots. However, the small size of such clusters (<2 nm), and the large surface-to-bulk ratio significantly limit characterisation techniques that can be utilised. Here we demonstrate how a combination of EXAFS and XANES can be used to obtain information about sample stoichiometry and cluster symmetry. Investigating two types of clusters that show sharp UV-vis absorption peaks at 311 nm and 322 nm, we found that both samples possess approximately 2:1 Cd:S ratio and have similar nearest-neighbour structural arrangements. However, both samples demonstrate a significant departure from the tetrahedral structural arrangement, with an average bond angle determined to be around 106.1 degree showing a bi-fold bond angle distribution. Our results suggest that both samples are quazi-isomers. Their core structure has identical chemical composition but a different atomic arrangement with distinct bond angle distributions.

The counterintuitive phenomenon of pressure-induced softening in materials is likely to be caused by the same dynamical behavior that produces negative thermal expansion. Through a combination of molecular dynamics simulation on an idealized model and neutron diffraction at variable temperature and pressure, we show the existence of extraordinary and unprecedented pressure-induced softening in the negative thermal expansion material scandium fluoride ScF_{3}. The pressure derivative of the bulk modulus B, B^{'}=(∂B/∂P)_{P=0}, reaches values as low as -220±30 at 50 K, and is constant at -50 between 150 and 250 K.

The possible structures of (CdSe)(n) and (CdS)(n) (n up to 34) nanoclusters were systematically studied using the ab initio random structure searching (AIRSS) method. We have been able to find stable, symmetric nanoclusters not previously discovered; using the computed pair distribution functions, we have put forward a hypothesis for the increased stability of these clusters. We have also been able to investigate structural features of the transformation to the bulk: for (CdS)(n) with n < 16 and (CdSe)(n) with n < 21, structures based on rings and cages with coordination number up to 3 are favored, while for larger n, the minimum-energy structures are more bulklike with an average coordination number larger than 3. This indicates a gradual transformation from a cagelike structure to a bulklike structure as the number of atoms increases. One striking finding was that for any value of n, the range of structures formed a continuous distribution of cluster energies rather than there being significant energy differences between them. This work created an extensive database of benchmarks and candidate structures for these systems.

Four types of magic-size CdS clusters and three different CdS quantum dots have been studied using the technique of X-ray total scattering and pair distribution function analysis. We found that the CdS quantum dots could be modelled as a mixed phase of atomic structures based on the two bulk crystalline phases, which is interpreted as representing the effects of random stacking of layers. However, the results for the magic-size clusters are significantly different. On one hand, the short-range features in the pair distribution function reflect the bulk, indicating that these structures are based on the same tetrahedral coordination found in the bulk phases (and therefore excluding new types of structures such as cage-like arrangements of atoms). But on the other hand, the longer-range atomic structure clearly does not reflect the layer structures found in the bulk and the quantum dots. We compare the effect of two ligands, phenylacetic acid and oleic acid, showing that in one case the ligand has little effect on the atomic structure of the magic-size nanocluster, and in another it has a significant effect.

The crystal structure of the low-temperature [Formula: see text] phase of crystalline malononitrile, CH2(CN)2 (stable phase below 260 K), has been determined using Rietveld refinement on neutron powder diffraction data. The [Formula: see text] phase has a slightly lower density than the other three low-pressure phases, and unlike those phases it has a polar structure. The transition from the [Formula: see text] to [Formula: see text] phase involves a major reconstruction of the structure, including establishing a network of hydrogen bonds. DFT simulations of the structure and phonon dispersion curves of both [Formula: see text] and [Formula: see text] phases give free energy curves consistent with the phase transitions. It is noted that the transition from the [Formula: see text] to [Formula: see text] phase at 260 K is facilitated by the entropy arising from the low-frequency phonons associated with the soft mode for the sequence of [Formula: see text]-[Formula: see text]-[Formula: see text] phase transitions.

Structural isomerism of colloidal semiconductor nanocrystals has been largely unexplored. Here, we report one pair of structural isomers identified for colloidal nanocrystals which exhibit thermally-induced reversible transformations behaving like molecular isomerization. The two isomers are CdS magic-size clusters with sharp absorption peaks at 311 and 322 nm. They have identical cluster masses, but slightly different structures. Furthermore, their interconversions follow first-order unimolecular reaction kinetics. We anticipate that such isomeric kinetics are applicable to a variety of small-size functional nanomaterials, and that the methodology developed for our kinetic study will be helpful to investigate and exploit solid–solid transformations in other semiconductor nanocrystals. The findings on structural isomerism should stimulate attention toward advanced design and synthesis of functional nanomaterials enabled by structural transformations.