An ultra-sound scanning in vivo light source

 

Advances concerning the interaction of technological devices with biological tissues still face significant limitations. In many cases, researchers must choose between achieving high spatiotemporal imaging resolution and using flexible systems capable of investigating multiple regions of the body. While implantable devices provide cellular-level precision, they are invasive and restricted to highly localized sites, making them ill-suited for investigation of dynamic or spatially distributed biological processes.

In this work, researchers at Stanford University developed a material capable of emitting light within tissues using focused ultrasound. To achieve this, they synthesized biocompatible mechanoluminescent nanotransducers (MLNTs), composed of Sr₄Al₁₄O₂₅:Eu,Dy, derived from bulk material. The surface of the nanoparticles was functionalized with polyethylene glycol (PEG), forming a stable colloidal dispersion in an aqueous medium. These particles exhibited sizes ranging from 30 to 110 nm and stability of up to one week, retaining the same diffraction patterns and emission spectra as the bulk material.

Experimental validation was carried out in mice injected with MLNTs and stimulated with focused ultrasound. As a demonstration, the researchers were able to observe the three-dimensional distribution of different regions in the brains of living animals. Ultrasound, which can penetrate tissues and can be precisely focused, is thus confirmed as a powerful non-invasive tool for studying biological processes.

The authors propose that light emission originates when ultrasound induces mechanical deformations that activate energy traps in the material. This process involves electric fields generated by the movement of dislocations associated with intergranular sliding. The hypothesis is consistent with the observed proportional relationship between the intensity of emitted light and ultrasonic pressure. They additionally observed that by increasing the ultrasound frequency, the luminous spot decreased in size, allowing the light emission to be tuned in a manner analogous to optical focusing with lenses.

The ability to generate light within biological tissues in a controlled spatiotemporal manner opens applications in gene editing, photodynamic therapy, deep-tissue imaging, and drug delivery, laying the groundwork for new reconfigurable light-based biotechnologies.

For further information, consult: Nature Materials

Grain boundary stabilization of ultrathin ferroelectric ZrO₂ films

 

Grain boundaries (GBs) are ubiquitous topological defects in polycrystalline materials that play a crucial role in determining their macroscopic properties, such as mechanical strength, radiation tolerance, and thermal conductivity. For example, dense networks of GBs hinder dislocation motion, thereby hardening and strengthening nanostructured metals and superhard materials.

Defect engineering and microstructural modification have traditionally treated GBs simply as auxiliary elements for tuning material properties. However, recent studies suggest that GBs not only act as secondary regulators but also as independent heterointerfaces capable of stabilizing grain phase structures and inducing emergent functionalities.

The possibility of controlling crystalline phases through GB manipulation gained relevance with the discovery of ferroelectricity in nanocrystalline fluorite-based films of HfO₂ and ZrO₂, where ferroelectricity arises in a metastable, non-centrosymmetric orthorhombic (O) phase. However, the role of GBs in stabilizing the O-phase at the nanoscale has been scarcely explored, partly due to the difficulty of accurately determining their atomic-scale structure and chemical composition.

A group of researchers in China succeeded in growing, by chemical methods, an ordered La(Sr)–Mn–O superstructure exclusively at the GBs of ultrathin polycrystalline ZrO₂ films (with thicknesses below 5 nm), which stabilizes the metastable ferroelectric O-phase. The atomic configurations of the La(Sr)–Mn–O superstructure and its ordered growth were identified using atomic-resolution imaging and electron energy loss spectroscopy (EELS). Charge distribution and Mn–O electronic interactions were confirmed using four-dimensional scanning transmission electron microscopy (4D-STEM). First-principles calculations demonstrate an ordered arrangement of the eg/t2g orbitals of Mn³⁺/Mn⁴⁺ ions along the GBs. This arrangement induces alternating interactions with oxygen ions, periodically modulating the strength of Zr–O bonds and ultimately stabilizing the ferroelectric state on both sides of the GBs.

These findings propose a stabilization mechanism for metastable polar phases through a novel grain boundary chemistry, opening pathways toward ultra-stable nanoelectronics.

For further information go to: Nature Materials

Practical lithium–organic batteries enabled by an n-type conducting polymer

 

Currently, the widespread use of portable electronic devices demands batteries with higher storage capacities and longer lifetimes. Among the various options available on the market, lithium-ion batteries (LIBs) stand out due to their high energy storage capacity and long service life. However, these devices are typically composed of inorganic materials derived from limited mineral resources, which leads to negative environmental impacts. For this reason, research efforts have been directed toward finding more sustainable and environmentally friendly alternatives.

Scientists from several Chinese universities have developed organic lithium batteries using an n-type conductive polymer, poly(benzodifurandione) (PBFDO). PBFDO exhibits excellent ionic and electronic transport properties, high electrical conductivity (>2000 S/cm), low solubility in liquid electrolytes, and thermal structural stability up to 200 °C. The researchers constructed polymer cathodes with an ultrahigh mass loading of up to 206 mg/cm², achieving a specific capacity of 42 mAh/cm². In addition, 2.5 Ah lithium-organic pouch cells were fabricated with an energy density of 255 Wh/kg, comparable to that of commercial lithium-ion batteries.

The results reveal π–π stacking of the (010) planes with interplanar distances of 0.34 nm and lamellar stacking of the (100) planes with interplanar distances of 1.04 nm. Within these stacked structures, channels containing a large number of carbonyl groups are formed, which are attributed to enabling efficient lithium transport. These cells demonstrated strong cycling stability, resistance to nail penetration without explosion or fire, and efficient performance across an extreme temperature range (−70 °C to 80 °C). The flexibility of the PBFDO cathodes was also highlighted, making them suitable for applications in portable electronics. Furthermore, the energy storage mechanism of PBFDO was investigated, showing that carbonyl groups act as active sites for lithium-ion storage.

This work opens the door to the use of n-type conductive polymers as electrodes in LIBs, since the type of charge carriers (electrons) helps maintain charge balance when Li⁺ is inserted into the electrode, in contrast to p-type conductive polymers whose charge carriers (holes) make charge balance more difficult.

More information at: NATURE

Consolidating mural plaster layer with nanolime

 

Treatment of the mural plaster layer with NL. a) Spraying of NL dispersion on the surface of the mural plaster layer. b) Spraying deionized water onto the surface after 10 min the application of the NL dispersion. c) Mural plaster layer, with NL applied for consolidation in samples 1, 2, and 3. d) Mural plaster layer after consolidation. e), f), g) Samples 1, 2, and 3 before consolidation, respectively. h), i), j) Samples 1, 2, and 3 after consolidation, respectively. k) Mural pigment layer of samples 1, 2, and 3.

The pigment of many ancient mural paintings rests on a layer of lime and clay known as plaster, which deteriorates with aging, leading to a decrease in its mechanical strength. A team of researchers from China and Spain studied methods to strengthen the plaster layer using lime nanoparticles or nanolime (NL), a dispersion of calcium hydroxide nanoparticles. NL overcomes the limitations of other consolidants, such as organic materials or acrylic resins, which reduce the breathability of the material and, over time, generate new aging-related problems.

The researchers developed a synthesis procedure to produce NL with uniform size and morphology by using different additives, ultrasonic treatment, and centrifugation. As a result, they obtained nanoparticles of approximately 40 nm in diameter—significantly smaller than the 180 nm obtained without centrifugation. A dispersion of nanolime in ethanol was sprayed with an atomizer onto the plaster layers of fragments from a Chinese mural painting, which were later sprayed with water to accelerate the consolidation of the plaster.

The results showed that the selected nanolime penetrated to a depth of 1.2–3.5 mm, and the surface hardness of the layer increased by approximately 56%. Porosity decreased only minimally (around 5.9%); a slight shift toward smaller pores was observed, indicating effective filling of the structure. Microstructural analysis confirmed the densification of the surface layers after consolidation. No whitening of the pigment layer on the surface of the plaster was observed.

The authors concluded that the nanoparticle-sized selected NL provides high-quality consolidation of mural painting plaster and may serve as a methodological alternative for broader application in the conservation of cultural heritage, including murals detached from their original support and preserved in museums.

For further information go to: JOURNAL OF CULTURAL HERITAGE

Polyethylene terephthalate waste-derived carbon dots with enhanced photoluminescence

 

Carbon dots (CDs) are photoluminescent carbon nanoparticles, smaller than 10 nm, that have gained relevance in nanotechnology due to their chemical stability, low production cost, biocompatibility, and tunable optical properties. Thanks to these characteristics, CDs are used in fields such as bioimaging, sensors, optoelectronics, and catalysis. A particularly attractive aspect is that they can be obtained from waste, making them functional materials aligned with the principles of circular economy.

In a recent work, a group of researchers from UNAM’s Center for Nanosciences and Nanotechnology reported the transformation of polyethylene terephthalate (PET) waste into highly luminescent CDs. In previous studies, PET has been used in the form of large fragments from crushed bottles (C-PET), which leads to non-uniform heat transfer and chemical diffusion during synthesis. The central idea of the present work is that the size of the polymeric precursor plays a key role in the final quality of the nanomaterial.

In this study, the authors used micronized PET (M-PET), that is, PET ground into micrometric particles, and directly compared it with PET cut into fragments (C-PET). They analyzed two chemical routes: surface oxidation with hydrogen peroxide and nitrogen doping using ethylenediamine. This experimental design allowed to understand how precursor size and surface functionalization affect the structural and optical properties of the CDs.

Additionally, biocompatibility and cellular internalization of CDs were evaluated using macrophages and epithelial cells.

The results showed that CDs derived from M-PET are smaller, more crystalline, and considerably brighter. In particular, oxidized CDs produced from M-PET reached a quantum yield close to 52%, approximately 2.4 times higher than those obtained with C-PET. Moreover, they revealed photoluminescent emission at different excitation wavelengths between 260 and 380 nm, indicating a more homogeneous structure with fewer electronic defects. On the other hand, nitrogen-doped CDs showed an additional emission in the near-infrared and excitation-dependent fluorescence. However, they displayed higher cytotoxicity in epithelial cells. It is important to note that both types of particles were sensitive to pH changes, a crucial characteristic for applications in biological environments where pH may vary.

This study demonstrates that both precursor engineering and synthesis chemistry are important. Micronizing PET significantly enhances the optical performance of CDs without resorting to aggressive or unsustainable processes.

For further information go to:  Carbon

Real-space observation of ultrastrong coupling between optical phonons and surface plasmon polaritons

 

The physical and chemical properties of atoms and molecules are determined by their energy levels. If these levels can be controlled, it becomes possible to modify material properties, which has important applications in materials science, chemistry, and photonics.

A modern approach to achieving such control is based on the strong and ultrastrong coupling between light and matter. In this regime, energy is coherently exchanged between the two systems, giving rise to Rabi oscillations and to the formation of hybrid light–matter states known as polaritons. In this process, various excitations arising from light–matter interactions may participate, such as excitons, plasmons, phonons, and molecular vibrations.

In this work, researchers from Spain and France present a nano-spectroscopic technique based on nanoscale Fourier-transform infrared spectroscopy (nano-FTIR). This technique enables real-space mapping of the ultrastrong vibrational coupling between the optical phonons of a thin SiC layer and the surface plasmon polaritons of an InAs semiconductor substrate.

This ultrastrong coupling, which occurs when a system is photoexcited, takes place over a wide range of wave vectors and gives rise to a large number of hybrid modes (mixtures of light and matter). In particular, when light couples to molecular vibrations or to lattice vibrations (phonons), changes in chemical reactivity have been observed. This facilitates the study of polaritonic chemistry, in which light modifies the behavior of material systems, and may even lead to theoretically predicted phase transitions induced by strong and ultrastrong coupling.

These results are relevant for a wide range of applications, including ultrasensitive sensors, nonlinear optics, and quantum technologies.

For further information go to: Nature materials

Electrogenerated Excitons for Tuning Lanthanide Electroluminescence

 

At present, the most common sources of lighting come from modern photonic devices based on light-emitting diode (LED) technology, which converts electrical energy into photons by using the electroluminescence (EL) phenomenon of certain materials. Although major technological advances have been achieved, improving LEDs to obtain a broader color palette with more intense and vivid colors, increase their operational lifetime, and enable optimized production, poses a challenge with the use of conventional materials. One current strategy relies on using insulating nanoparticles that contain ions from the lanthanide group. As the periodic table shows, this group comprises 14 chemical elements from lanthanum to ytterbium.

Lanthanide-doped nanocrystals offer a fundamentally different approach to EL engineering. The 4f–4f transitions of lanthanides yield narrow emission lines (<10 nm bandwidth), with photochemical and thermal stability, long excited-state lifetimes, and defect-insensitive emission—features that are advantageous for spectrally precise and stable EL operation.

However, the insulating nature of these nanocrystals presents a challenge for charge transport and injection, hindering their application in electrically driven optoelectronic devices.

Researchers from China and Singapore demonstrated efficient EL by doping insulating (4 nm) NaGdF₄:X nanocrystals with X = Tb³⁺, Eu³⁺, or Nd³⁺, and coating them with a series of functionalized 2-(diphenylphosphoryl)benzoic acid ligands (ArPPOA). These ligands, composed of phosphine oxide groups with carboxyl and P=O coordination sites, exhibit hybrid donor–acceptor character that effectively sensitizes the luminescence of lanthanide nanocrystals by modulating charge transfer between ligands. Ultrafast spectroscopy studies revealed that the strong coupling between ArPPOA and the lanthanide nanocrystals facilitates sub-nanosecond intersystem crossing and highly efficient triplet-to-nanocrystal energy transfer (up to 96.7%). Through careful control of dopant composition and concentration within the nanocrystals, the researchers achieved broadband multicolor EL without altering the device architecture, reaching an external quantum efficiency above 5.9% for Tb³⁺.

This platform of functionalized nanocrystals provides a modular strategy for exciton (electron–hole pair) control in insulating nanocrystal systems, offering a route to electroluminescent materials with precise emission spectra.

This work was published in Nature

Additional information can be found in Nature