Micro, Volume 5, Issue 1 (March 2025) – 14 articles

Carbon dots (CDots) are classically defined as small carbon nanoparticles with effective surface passivation, which, in the classical synthesis, has been accomplished by surface organic functionalization. CDot-like nanostructures could also be produced by the thermal carbonization processing of selected organic precursors, in which the non-molecular nanocarbons resulting from the carbonization are embedded in the remaining organic species, which may provide the passivation function for the nanocarbons. In this work, a mixture of oligomeric polyethylenimine and citric acid in the solid state was used for efficient thermal carbonization processing with microwave irradiation under various conditions to produce dot samples with different nanocarbon content. The samples were characterized in terms of their structural and morphological features regarding their similarity or equivalency to those of the classical CDots, along with their significant divergences. Also evaluated were their optical spectroscopic properties and their photoinduced antimicrobial activity against selected bacterial species. The advantages and disadvantages of the thermal carbonization processing method and the resulting dot samples with various features and properties mimicking those of classically synthesized CDots are discussed. Full article

The spray pyrolysis deposition of nanostructured Pb_1−xSn_xSe alloy films, x = 0.0 to 1.0, from as-prepared Pb_1−xSn_xSe alloy colloids as the starting solution is reported. The colloidal dispersions were prepared by dissolving selenium in an amine–thiol mixture, reacted with the Sn and Pb precursors in propylene glycol, and subsequently sprayed onto glass substrates at 300 °C. Structural characterization indicated the formation of the alloyed rock-salt cubic phase for 0.0 ≤ x ≤ 0.75, oxidized Pb and Se phases produced during the deposition, and only orthorhombic SnSe for x = 1.0 with Se and SnSe₂ as impurities. Nanocrystalline films ranging from 16 to 16.5 nm in size were obtained. The films displayed a shift in their optical structure and a non-monotonic variation in the band gap energy, first a decrease, reaching the minimum at x = 0.30 and a further increase in the Sn content. The decrease in the optical band gap resembles that of a topological insulator behavior. The morphology of the alloyed films confirmed the large nanocrystal formation by self-assembly processes in both the PbSe and SnSe phases and segregated PbSnSe platelets for x ≥ 0.30. Seebeck coefficient revealed that a typical semiconductor behavior dominated by bipolar transport, and p-type conductivity, but only for x = 0.0 n-type conductivity was exhibited. The maximal Seebeck coefficient magnitude behaved similarly to the band gap energy, evidencing the influence of energy band structure and the topological character. Full article

Polyvinylidene fluoride (PVDF) is a multifunctional polymer renowned for its unique electrical, mechanical, and piezoelectric properties, making it an attractive candidate for various applications. Although the spin-coating method has been the conventional method for fabricating PVDF thin films, this work is the first to apply the dip-coating technique with humidity control, which is a largely unexplored method in the literature on PVDF thin films. This novel approach offers great prospects for improved control and performance adjustments, as well as expanding the range of film deposition procedures. Here, we examine the phase composition of PVDF thin films; adjust different parameters to optimize the electroactive phases fraction, especially the Beta phase; and examine how relative humidity affects the properties of the film. Moreover, we test the impact of different nanoparticles’ addition on the phases fraction and characteristics of the film. Furthermore, we analyze the topography of the resultant films using several approaches, providing fresh insights into their structural features. Full article

The cosmetic market is constantly evolving and ever-changing, particularly with the introduction and incorporation of nanotechnology-based processes into cosmetics for the production of unique formulations with both aesthetic and therapeutic benefits. There is no doubt that nanotechnology is an emerging technology for cosmetic formulations. Among the numerous cosmetic items, incorporating nanomaterials has provided a greater scope and is commonly utilized in facial masks, hair products, antiaging creams, sunscreen creams, and lipsticks. In cosmetics, nanosized materials, including lipid crystals, liposomes, lipid NPs, inorganic nanocarriers, polymer nanocarriers, solid lipid nanocarriers (SLNs), nanostructured lipid carriers (NLCs), nanofibers, nanocrystals, and nanoemulsions, have become common ingredients. The implementation of nanotechnology in the formulation of face masks will improve its efficacy. Nanotechnology enhances the penetration of active ingredients used in the preparation of face masks, such as peel-off masks and sheet masks, which results in better effects. The emphasis of this review is mainly on the formulation of cosmetic face masks, in which the impact of nanotechnology has been demonstrated to improve the product performance on the skin. Full article

Escherichia coli (E. coli) and Agrobacterium tumefaciens (A. tumefaciens) are bacterial species commonly found in the environment, and they can do much harm to humans, animals and plants. As a result, it is necessary to find an accurate, rapid, simple method to detect the concentrations of them, and polymerase chain reaction (PCR) is one of the most suitable candidates. In this study, a gold nanoparticles (GNPs) enhanced polymerase chain reaction was developed, to simultaneously target the specific genes, 16S rDNA of E. coli and Tms1 of A. tumefaciens. PCR amplification times (CT values) of E. coli and A. tumefaciens were seen to be lowered significantly by the incorporation of GNPs. The fluorescence intensities in quantitative PCR amplifications of both E. coli and A. tumefaciens reached the maximum after around 40 cycles, and the PCR yield (maximum fluorescence intensity) was proportional to the maximum absorbance at 495 nm in the corresponding UV-vis spectra. GNPs were found to enhance the PCR yield of both E. coli and A. tumefaciens, and smaller sized GNPs (average 13 nm) showed a better enhancement effect compared to larger sized GNPs (average 30 nm). Conventional PCR showed that both E. coli and A. tumefaciens could be detected together with limit of detection of 10 CFU/mL for each bacterium, using GNPs of 13 nm. The results of this study could lead to improvement of multiplex PCR that can detect different bacteria species simultaneously. Full article

Microscale systems have been underexplored in contemporary regenerative therapies developed to treat vision loss. The pairing of in vitro cell systems with optical fluorescent imaging provides unique opportunities to examine the infiltration of donor stem cells needed for successful transplantation therapies. A parallel eye device was developed to provide electric field (EF) stimulation to guide the migration of cells within 3D eye facsimiles synthesized from different ocular biomaterials. Cell infiltration within facsimiles was rapidly resolved using confocal microscopy to eliminate dependence on the cryostat sectioning commonly used for cell study. Moreover, EF stimulated galvanotaxis of donor cells within different depths of eye facsimiles. Optical imaging provided rapid resolution of z-stack images at physiologically appropriate depths below 500 microns. This study demonstrates that paired microscale–optical systems can be developed to elucidate understudied transplantation processes and improve future outcomes in patients. Full article

Any application of nanoparticles is influenced by the unavoidable tendency of these particles to agglomerate. As a result, one obtains a more or less broad distribution of agglomerate sizes. This may influence the properties significantly. Looking at agglomeration processes, one has to distinguish two different phenomena: the generally discussed problem, where each particle has the chance to combine with any other particle, or the case, where an agglomeration is possible only with direct neighbors. The latter case, which is the subject of this study, is observed when the particles are stored in a box. In contrast to conventional analyses, the calculations for this paper are based on Markov chain Monte Carlo calculations. This paper describes the formation and development of these agglomerates and the resulting distributions. For an improved depiction of the results, a new quantity derived from entropy, the ‘integral entropy’, was developed. This quantity allows efficient visualization of the development of the agglomerates as a function of the iteration steps resulting from these calculations; additionally, applying the integral reduces the statistical scattering of the results. Furthermore, different mechanisms and interaction parameters were assumed and compared. The results were analyzed to show progress that depends on the number of iteration steps. An important result of these calculations is the distribution of agglomerate sizes and the number of agglomerates as a function of the number of iterations. The calculations are based on different assumptions on the agglomeration and arrangements of the particles. Full article

In recent years, various types of sensors have been developed at both millimeter (mm) and micrometer (µm) scales for numerous biomedical applications. Each design has its own advantages and limitations. This study compares the electrical characteristics and sensitivity of millimeter- and micrometer-scale sensors, emphasizing the superior performance of millimeter-scale designs for detecting type-2 diabetes. Elevated glucose levels in type-2 diabetes alter the complex permittivity of red blood cells (RBCs), affecting their rheological and electrical properties, such as viscosity, volume, relative permittivity, dielectric loss, and AC conductivity. These alterations may manifest as a unique bio-impedance signature, offering a diagnostic topology for diabetes. In view of this, various concentrations (ranging from 10% to 100%) of 400 µL of normal and diabetic RBCs suspended in phosphate-buffered saline (PBS) solution are examined to record the changes in bio-impedance signatures across a spectrum of frequencies, ranging from 1 MHz to 10 MHz. In this study, simulations are performed using the finite element method (FEM) with COMSOL Multiphysics^® to analyze the electrical behavior of the sensors at both millimeter (mm) and micrometer (µm) scales. These simulations provide valuable insights into the performance parameters of the sensors, aiding in the selection of the most effective design by using this topology. Full article

Quercetin, a flavonoid, has well-proven cytotoxicity potential, but its therapeutic efficacy is hampered by hydrophobicity, stability issues, and lower bioavailability. The present research aims to address these issues and formulation barriers by formulating a quercetin-loaded micellar nanogel. Quercetin was encapsulated in PF 68 micelles to enhance its solubility, loading, and stability to better its therapeutic potential. The nanogel was further characterized regarding for pH, spreadability, and in vitro cytotoxicity against human breast cancer cells (MCF-7). The resulting micelles exhibited a particle size of 180.26 ± 2.4 nm, surface charge of −13.5 mV, entrapment efficiency of 78.4 ± 1.2%, and in vitro release of 96.11 ± 0.75% up to 8 h. This in vitro cytotoxicity study on MCF-7 cell lines reveals the improved TGI and GI 50 values of micellar nanogel formulation compared to quercetin. The overall study results demonstrated that the developed micellar nanogel system might serve as a promising nanocarrier to enhance the cytotoxic potential of quercetin in cancer therapy. Full article

This work determined the resistance of paint formulations containing TiO₂ particles to fungal growth. Siloxane, acrylic and silicone paints were placed outdoors, and the fungal species growing thereon were recorded after 3, 6 and 9 months. In addition, three paint types containing TiO₂ with/without biocide were inoculated with fungal spores and irradiated using UV. Acrylic paints were also doped with different metals and were inoculated and incubated under fluorescent light. Following outdoor incubation, the silicone paint was the least colonised by different fungal species. The species most recovered from the surfaces were Aspergillus spp. and Penicillium spp. Following UV irradiation on different paints containing biocide and/or a photocatalyst, no fungal growth was demonstrated on some of the paint combinations. When the paint samples were doped with different metals and incubated using light, the sample most efficient at preventing fungal growth contained lanthanum (0.004%). The paint samples containing praseodymium (light:1.72) facilitated the densest fungal colonies. Most of the surfaces demonstrated heterogeneous coverage by the fungi. The most clustered fungal colonisation was on surfaces incubated in the light. This work demonstrated that fungal colonisation on paints changed over time and that the antimicrobial efficacy of TiO₂ was affected by the chemical composition, biocide and doping of the paint. Full article

The catalytic conversion of carbon dioxide (CO₂) into carbon monoxide (CO) via the reverse water–gas shift (RWGS) reaction offers a promising pathway toward a sustainable carbon cycle. However, the competing Sabatier reaction presents a significant challenge, underscoring the need for highly efficient catalysts. In this study, we developed a novel catalyst comprising cobalt-oxide-supported nickel-hydroxide nanoparticles (denoted as Co@Ni). This catalyst achieved a remarkable CO production yield of ~5144 μmol g⁻¹ at 573 K, with a CO selectivity of 77%. These values represent 30% and 70% improvements over carbon-supported Ni(OH)₂ (Ni-AC) and CoO (Co-AC) nanoparticles, respectively. Comprehensive physical characterizations and electrochemical analyses reveal that the exceptional CO yield of the Co@Ni catalyst stems from the synergistic electronic interactions between adjacent active sites. Specifically, cobalt-oxide domains act as electron donors to Ni sites, facilitating efficient H₂ splitting. Additionally, the oxygen vacancies in cobalt oxide enhance CO₂ adsorption and promote subsequent dissociation. These findings provide critical insights into the design of highly efficient and selective catalysts for the RWGS reaction, paving the way for advancements in sustainable carbon utilization technologies. Full article

This work addresses a critical challenge in microscale computational electromagnetics for liquid crystal-based reconfigurable components: the inadequate capability of current software to accurately identify and simulate higher-order modes (HoMs) in complex electromagnetic structures. Specifically, commercial simulators often fail to capture modes such as Transverse Electric (TE11) beyond the fundamental transverse electromagnetic (TEM) mode in coaxial liquid crystal phase shifters operating in the terahertz (THz) regime, leading to inaccurate performance predictions and suboptimal designs for telecommunication engineering applications. To address this limitation, we propose a novel diagnostic methodology incorporating three lossless assumptions to enhance the identification and analysis of pseudo-HoMs in full-wave simulators. Our approach theoretically eliminates losses associated with metallic conductivity, dielectric dissipation, and reflection effects, enabling precise assessment of frequency-dependent HoM power propagation alongside the primary TEM mode. We validate the methodology by applying it to a coaxially filled liquid crystal variable phase shifter device structure, underscoring its effectiveness in advancing the design and characterization of THz devices. This work provides valuable insights for researchers and engineers utilizing closed-source commercial simulators in micro- and nano-electromagnetic device development. The findings are particularly relevant for microscale engineering applications, including millimeter-wave (mmW), sub-mmW, and THz systems, with potential impacts on next-generation communication technologies. Full article

Due to their biocompatibility, nontoxicity, and surface conjugation properties, nanomaterials are effective nanocarriers capable of encapsulating chemotherapeutic drugs and facilitating targeted delivery across the blood–brain barrier (BBB). Although research on nanoparticles for brain cancer treatment is still in its early stages, these systems hold great potential to revolutionize drug delivery. Glioblastoma multiforme (GBM) is one of the most common and lethal brain tumors, and its heterogeneous and aggressive nature complicates current treatments, which primarily rely on surgery. One of the significant obstacles to effective treatment is the poor penetration of drugs across the BBB. Moreover, GBM is often referred to as a “cold” tumor, characterized by an immunosuppressive tumor microenvironment (TME) and minimal immune cell infiltration, which limits the effectiveness of immunotherapies. Therefore, developing novel, more effective treatments is critical to improving the survival rate of GBM patients. Current strategies for enhancing treatment outcomes focus on the controlled, targeted delivery of chemotherapeutic agents to GBM cells across the BBB using nanoparticles. These therapies must be designed to engage specialized transport systems, allowing for efficient BBB penetration, improved therapeutic efficacy, and reduced systemic toxicity and drug degradation. Lipid and inorganic nanoparticles can enhance brain delivery while minimizing side effects. These formulations may include epitopes—small antigen fragments that bind directly to free antibodies, B cell receptors, or T cell receptors—that interact with transport systems and enable BBB crossing, thereby boosting therapeutic efficacy. Lipid-based nanoparticles (LNPs), such as liposomes, niosomes, solid lipid nanoparticles (SLNs), and nanostructured lipid carriers (NLCs), are among the most promising delivery systems due to their unique properties, including their size, surface modification capabilities, and proven biosafety. Additionally, inorganic nanoparticles such as gold nanoparticles, mesoporous silica, superparamagnetic iron oxide nanoparticles, and dendrimers offer promising alternatives. Inorganic nanoparticles (INPs) can be easily engineered, and their surfaces can be modified with various elements or biological ligands to enhance BBB penetration, targeted delivery, and biocompatibility. Strategies such as surface engineering and functionalization have been employed to ensure biocompatibility and reduce cytotoxicity, making these nanoparticles safer for clinical applications. The use of INPs in GBM treatment has shown promise in improving the efficacy of traditional therapies like chemotherapy, radiotherapy, and gene therapy, as well as advancing newer treatment strategies, including immunotherapy, photothermal and photodynamic therapies, and magnetic hyperthermia. This article reviews the latest research on lipid and inorganic nanoparticles in treating GBM, focusing on active and passive targeting approaches. Full article

This study aimed to characterize the temporal and spatial occurrence of microplastics on the beaches of the Caribbean coast of Limón, Costa Rica. The selected beaches comprise a stretch of 70 km, characterized by large environmental protection areas, agricultural and residential areas with low occupation density, urban areas, and port areas. Despite the great importance of the beaches for the country, studies related to solid waste pollution remain scarce on the Caribbean coast. The methodology consisted of conducting fieldwork in 2017 and 2019 to collect materials on five beaches and laboratory analyses for extraction using hypersaline solution and the quantification and characterization of microplastics based on type, size, and color. The results show that the beaches studied in the northwestern sector had the highest concentrations of microplastics, with emphasis on Cieneguita Beach and Airport Beach, with a predominance of pellets (56.7%) followed by fragments (21.8%). These beaches are inserted in a coastal stretch with a strong concentration of industrial, port, and airport activities. The lower occurrence of microplastics in the southeastern sector (Manzanillo and Gandoca) may be related to the greater number of preservation areas. With varying sizes, shapes, and colors, most microplastics had a worn appearance, which suggests reworking by coastal processes and subsequent deposition on the studied beaches. The impact of this type of pollution on the coast of Limón is notorious and shows the need for further research into the occurrence and distribution of microplastics on Caribbean beaches so that possible sources and damage to coastal ecosystems can be identified. Full article