martes, 29 de julio de 2025

Flexible Selenium Nanowires with Tuneable Electronic Bangaps

 Gráfico, Gráfico de dispersión

El contenido generado por IA puede ser incorrecto.

Changes in the size and geometric shape of nanoparticles allow for the manipulation of semiconductor properties without altering their chemical composition. However, a challenge remains: depending on the synthesis method, the size distribution of the nanoparticles can vary.

The use of nanotube molds to form selenium nanowires is part of a broader strategy that employs nanostructured templates to control the growth of one-dimensional nanomaterials.

Although selenium naturally crystallizes into elongated structures due to its anisotropic nature, templates such as carbon nanotubes (CNTs), anodic aluminum oxide, or other hollow nanostructures enable precise control over the nanowire’s unidirectional growth, size, orientation, and uniformity, while also protecting the material during formation. These core–shell structures, with a selenium core and a protective nanotube shell, have applications in nanoelectronics, photoconductors, and energy storage.

British researchers discovered distinct structural phases of selenium when confined within carbon and boron nitride nanotubes, observing remarkable structural plasticity in nanowires with diameters ranging from 0.4 to 3.0 nm. The experiment used one sample of boron nitride nanotube (BNNT) and four carbon nanotube (CNT) samples of different diameters, all under identical experimental conditions. Selenium was sublimed to fill the nanotubes, forming Se@CNT and Se@BNNT structures, in order to study exclusively the effect of nanotube diameter on the resulting selenium structure.

They found that the bandgap width of these nanowires, between 2.2 and 2.5 eV, depends non-monotonically on the diameter of the nanotube. This is due to conformational distortions in the selenium chains counteracting quantum confinement effects at sub-nanometric scales.

The authors developed a one-dimensional phase diagram that predicts the atomic structure of selenium as a function of the nanotube diameter, regardless of the host nanotube’s chemical composition. This demonstrates that confinement within nanotubes enables precise tuning of the structure and electronic properties of selenium. The materials were characterized using advanced electron microscopy and electron energy loss spectroscopy (EELS) to determine the bandgaps.

These nanoscale discoveries pave the way for the development of advanced, miniaturized, tunable, and flexible electronic components, such as transistors, optical sensors, and photovoltaic systems.


For further details, go to: Advanced Materials

miércoles, 25 de junio de 2025

Bipolar Cells of the Eye Treated with Plasmonic Gold Nanorods and Activated with Infrared Laser to Restore Vision

 Figure 1


Age-related macular degeneration (AMD) and retinitis pigmentosa are major causes of vision loss. Worldwide, AMD affects approximately 200 million people, and retinitis pigmentosa 1.5 million people.

In both conditions, there is a reduction in the sensitivity to light of retinal photoreceptors; however, certain retinal neurons such as bipolar and ganglion cells remain functional. This has sparked interest in research aimed at restoring vision.

A study conducted by researchers at Brown University in the United States points to a new type of visual prosthesis system that combines the use of plasmonic gold nanorods with a small laser device integrated into eyeglasses. 

The researchers injected gold nanorods into the vitreous humor of mice eyes, where the particles incorporated into the retina and into bipolar and ganglion cells. A scanning laser with wavelengths in the near-infrared region of the visible spectrum and a beam size of 20 microns was then used to focus infrared light onto the nanoparticles, generating a small amount of heat that activated the bipolar and ganglion cells. This activation pattern mimicked the natural visual signals processed by the brain through photoreceptor pulses.

Laser stimulation led to increased activity in the visual cortex of the mice indicating that previously absent visual signals were being transmitted and processed by the brain. 

The study found no signs of toxicity or inflammation over several months.

This finding suggests the potential application of a similar technology in humans. The use of near-infrared light, rather than visible light, is non-invasive and does not interfere with residual vision that the patient may still retain. Although further testing is needed before clinical application, the findings point to a less invasive option for vision restoration.


For more details, consult: 

ACS Nano

martes, 27 de mayo de 2025

Functional groups regulate ion concentration and pH in nanopores

 Diagrama

El contenido generado por IA puede ser incorrecto.

To understand the chemical reactions occurring inside the nanopores of nanostructured materials—whether synthetic or natural, such as those found in membranes or ion channels in biological systems—it is essential to determine the ion concentration within them. For this purpose, nanopores are functionalized with specific chemical groups.

Until now, it had not been possible to determine how functional groups influence ion concentration inside nanopores.

In this study, a group of researchers from the United States reported the development of a core–shell-type plasmonic nanosensor, consisting of a gold nanorod coated with mesoporous silica functionalized with phenyl and methyl groups. This nanosensor can measure the local concentration of protons, anions (such as phosphates, nitrates, sulfates, and arsenates), as well as cations (such as mercury, lead, and copper) in functionalized nanopores. The measurements were performed using Surface-Enhanced Raman Spectroscopy (SERS), applied in situ.

The obtained values were compared with those of bulk silica. Moreover, results indicated that ion concentrations differ in pristine and hydrophobic nanopores compared with those functionalized with phenyl and methyl radicals. In the latter, an increase in anion concentration and a concurrent decrease in cation concentration were reported. Additionally, the pH within the nanopores was found to depend on the composition of the solution. In some cases, the pH inside the nanopores decreased by as much as 2.5 units compared to the bulk value.

These findings provide insight into ion–nanopore chemical interactions and enable precise and selective control of contaminants, with direct applications in water chemistry for membrane-based desalination processes, CO₂ storage, and catalysis in porous materials.


More information at: ACS Applied Materials and Interfaces

miércoles, 14 de mayo de 2025

Ab initio structural solutions from nanocrystal powder diffraction using diffusion models

 Gráfico, Diagrama

El contenido generado por IA puede ser incorrecto.

Over the past century, the development of materials science has increasingly relied on the precise determination of atomic arrangements—that is, the crystal structure and its properties. To this end, X-ray diffraction (XRD) is commonly applied, with the sine qua non being the availability of a single crystal or monocrystal. However, this is not always feasible, especially with atomic clusters of nanometric size (smaller than 1000 Å), known as the nanostructure problem. In such cases, powder X-ray diffraction (PXRD) patterns are degraded due to peak broadening, intensity loss, and Bragg peak overlap.


Researchers from the United States and Germany have proposed a procedure that uses a generative machine learning model* based on diffusion processes, trained on 45,229 known structures. The model, called PXRDnet, conditioned solely on the compound's chemical formula, can solve simulated nanocrystals up to 10 Å in 200 materials with various symmetries and complexities, including all seven crystal systems.

PXRDnet correctly identifies structural candidates in 4 out of 5 cases, with an average error of just 7% in the Rietveld refinement factor R. Moreover, it is capable of resolving structures from noisy experimentally obtained diffraction patterns.


The authors argue that this data-driven, theoretically bootstrapped approach opens new avenues for determining previously unsolved nanomaterial structures. However, the model has limitations: it requires prior knowledge of the chemical formula and is restricted to structures with fewer than 20 atoms per unit cell.


*The term “generative” refers to a class of statistical models as opposed to discriminative models. Generative models can generate new data instances, while discriminative models distinguish between different types of data instances.


The work was published by Nature Materials


martes, 22 de abril de 2025

Synthesis of 2-Dimensional Metals via van der Waals (vdW) Compression

Since the discovery of graphene in 2004, two-dimensional (2D) materials have attracted considerable attention from the scientific community. To date, a wide variety of 2D materials are known, such as MXenes and transition metal dichalcogenides, as well as monolayers composed of a single type of atom from elements such as carbon (C), silicon (Si), germanium (Ge), and phosphorus (P). Most of these materials grow in three dimensions, forming structures stabilized by van der Waals (vdW) forces, which makes it relatively easy to exfoliate atomically thin layers.

However, this is not the case for metals, which grow three-dimensionally through strong chemical bonding. Until recently, it was believed that obtaining an atomically thin metal layer was practically impossible, as such structures would also be thermodynamically unstable.

Recently, a group of researchers in China succeeded in producing two-dimensional metals with thicknesses on the order of angstroms using a technique known as van der Waals compression. To carry out this process, they first grew a monolayer of molybdenum disulfide (MoS) on a sapphire substrate. This bilayer serves as a base or bottom anvil. A small amount of metal was then placed on the MoS monolayer and heated until it formed a molten droplet. A second MoS/sapphire layer was placed on top, with the MoS in direct contact with the molten metal. A pressure of 200 MPa was applied and maintained until both anvils returned to room temperature. The 2D metal was then obtained via a cleaving process that separated the MoS/2D-metal/MoS sandwich from the sapphire substrates.

Using this simple and effective technique, two-dimensional metals have been synthesized from bismuth (Bi), tin (Sn), lead (Pb), indium (In), and gallium (Ga). Transport properties measured via Raman spectroscopy on 2D bismuth revealed enhanced electrical conductivity, improved field-effect performance, and increased conductivity due to a nonlinear Hall effect.

This paves the way to a new line of research focused on exploring metals, alloys, and non-layered materials at the 2D scale, along with the investigation of their properties and potential implementation in various technological devices.

For further information go to: NATURE

viernes, 14 de marzo de 2025

Gold Nanoparticles Conjugated with Aptamers for Targeted microRNA Delivery Promote Dystrophic Muscle Regeneration

 figure 6



Duchenne muscular dystrophy is a genetic disorder characterized by the progressive loss of muscle mass due to mutations in the gene coding for dystrophin, a protein essential for muscle stability. In the absence of this functional protein, muscles cannot operate or repair properly, leading to deterioration of skeletal, cardiac, and pulmonary muscles.

Under normal conditions, when a healthy muscle is damaged, satellite cells are activated, differentiate, and contribute to muscle regeneration. This process helps maintain muscle integrity. However, in Duchenne muscular dystrophy, dystrophin is defective, making muscle fibers more vulnerable to damage. As a result, satellite cells remain continuously activated, leading to inflammation and, eventually, their exhaustion and death. Since satellite cells fail to differentiate, the muscle loses its ability to regenerate and, over time, is replaced by fibrotic and adipose tissue, contributing to the progressive deterioration of muscle tissue characteristic of the disease.

MicroRNAs are a class of RNA molecules involved in gene regulation that play crucial roles in the post-transcriptional regulation of genes. They inhibit messenger RNA (mRNA), preventing the production of defective proteins.  However, delivering them through the bloodstream is challenging due to their low stability and poor cellular penetration.

 A research team designed a strategy to treat muscular dystrophy using gold nanoparticles (AuNPs) as vehicles to transport therapeutic microRNAs into muscle cells. To specifically recognize these cells, the nanoparticles were functionalized with molecules called aptamers, which identify the α7/β1 integrin, a highly specific surface receptor expressed by muscle progenitors and differentiated myofibers, but virtually absent in other organs or tissues.

Once the system enters muscle stem cells, the nanoparticles release the microRNAs, which inhibit mRNA translation, preventing the synthesis of mutated (defective) dystrophin. As a result, satellite cells are not excessively activated but instead function in a regulated manner. 

The study investigated the system's activity in cellular and animal models, where muscle regeneration was observed at the cellular level, as well as functional recovery. The muscles of the treated mice improved and strengthened after treatment, increasing the functional capacity of the animals.


For further information, refer to: Nature Communications

miércoles, 26 de febrero de 2025

Design of a Low-Temperature Solar Heat Concentrator for the synthesis of ZnO nanostructures

 



Diagram and image of the CPC Solar Collector and SEM image of the synthesized ZnO

It has been widely reported that heat obtained from solar radiation can be applied to the synthesis of nanomaterials. In the case of zinc oxide (ZnO), the nanomaterial of interest in this study, it has previously been synthesized using high-temperature solar heat through Physical Vapor Deposition (PVD) methods.

In this work, a group of researchers from Mexico (CNyN-UNAM, CICESE, and UABC) propose evaluating a new approach for ZnO production through the design of a compound parabolic concentrator (CPC) with a cylindrical (tubular) receiver that generates heat at low temperatures.

The authors placed the precursors, zinc nitrate Zn(NO₃)₂ and sodium hydroxide (NaOH), inside the reactor where ZnO is produced. The reactor is in turn located within the CPC. In this setup, the collector serves both as a heat generator and as a reactor for synthesis.

The synthesis temperatures ranged from 50°C to 70°C. Using solar heat, pure ZnO crystalline clusters were obtained, with sizes ranging from 40.4 nm to 55.7 nm, and a band gap of 3.27 eV, slightly lower than that obtained by other methods at 50°C. The absorbance of the synthesized ZnO was 90%, regardless of the synthesis temperature.

This study confirmed that high-quality ZnO can be feasibly produced using low-temperature solar heat. This constitutes a new "green chemistry" approach and a renewable energy source for nanomaterial synthesis.

For more details, consult: Journal of Nanotechnology


Flexible Selenium Nanowires with Tuneable Electronic Bangaps

  Changes in the size and geometric shape of nanoparticles allow for the manipulation of semiconductor properties without altering their che...