Hexagonal Boron Nitride Quantum Dots Embedded on Layer-by-Layer Films for Peroxidase-Assisted Colorimetric Detection of β-Galactosidase Producing Pathogens

Pathogen detection has become a major research area all over the world for water quality surveillance and microbial risk assessment. Therefore, designing simple and sensitive detection kits plays a key role in envisaging and evaluating the risk of disease outbreaks and providing quality healthcare settings. Herein, we have designed a facile and low-cost colorimetric sensing strategy for the selective and sensitive determination of β-galactosidase producing pathogens. The hexagonal boron nitride quantum dots (h-BN QDs) were established as a nanozyme that showed prominent peroxidase-like activity, which catalyzes 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H2O2. The h-BN QDs were embedded on a layer-by-layer assembled agarose biopolymer. The β-galactosidase enzyme partially degrades β-1,4 glycosidic bonds of agarose polymer, resulting in accessibility of h-BN QDs on the solid surface. This assay can be conveniently conducted and analyzed by monitoring the blue color formation due to TMB oxidation within 30 min. The nanocomposite was stable for more than 90 days and was showing TMB oxidation after incubating it with Escherichia coli (E. coli). The limit of detection was calculated to be 1.8 × 106 and 1.5 × 106 CFU/mL for E. coli and Klebsiella pneumonia (K. pneumonia), respectively. Furthermore, this novel sensing approach is an attractive platform that was successfully applied to detect E. coli in spiked water samples and other food products with good accuracy, indicating its practical applicability for the detection of pathogens in real samples.

Role of transition metals in coinage metal nanoclusters for the remediation of toxic dyes in aqueous systems

A difficult issue in chemistry and materials science is to create metal compounds with well-defined components. Metal nanoclusters, particularly those of coinage groups (Cu, Ag, and Au), have received considerable research interest in recent years owing to the availability of atomic-level precision via joint experimental and theoretical methods, thus revealing the mechanisms in diverse nano-catalysts and functional materials. The textile sector significantly contributes to wastewater containing pollutants such as dyes and chemical substances. Textile and fabric manufacturing account for about 7 × 105 tons of wastewater annually. Approximately one thousand tons of dyes used in textile processing and finishing has been recorded as being discharged into natural streams and water bodies. Owing to the widespread environmental concerns, research has been conducted to develop absorbents that are capable of removing contaminants and heavy metals from water bodies using low-cost technology. Considering this idea, we reviewed coinage metal nanoclusters for azo and cationic dye degradation. Fluorometric and colorimetric techniques are used for dye degradation using coinage metal nanoclusters. Few reports are available on dye degradation using silver nanoclusters; and some of them are discussed in detailed herein to demonstrate the synergistic effect of gold and silver in dye degradation. Mostly, the Rhodamine B dye is degraded using coinage metals. Silver nanoclusters take less time for degradation than gold and copper nanoclusters. Mostly, H2O2 is used for degradation in gold nanoclusters. Still, all coinage metal nanoclusters have been used for the degradation due to suitable HOMO-LUMO gap, and the adsorption of a dye onto the surface of the catalyst results in the exchange of electrons and holes, which leads to the oxidation and reduction of the adsorbed dye molecule. Compared to other coinage metal nanoclusters, Ag/g-C3N4 nanoclusters displayed an excellent degradation rate constant with the dye Rhodamine B (0.0332 min-1). The behavior of doping transition metals in coinage metal nanoclusters is also reviewed herein. In addition, we discuss the mechanistic grounds for degradation, the fate of metal nanoclusters, anti-bacterial activity of nanoclusters, toxicity of dyes, and sensing of dyes.

Greening the pathways: a comprehensive review of sustainable synthesis strategies for silica nanoparticles and their diverse applications

Silica nanoparticles (SiNPs) have emerged as a multipurpose solution with wide-ranging applications in various industries such as medicine, agriculture, construction, cosmetics, and food production. In 1961, Stöber introduced a ground-breaking sol-gel method for synthesizing SiNPs, which carried a new era of exploration both in academia and industry, uncovering numerous possibilities for these simple yet multifaceted particles. Inspite of numerous reported literature with wide applicability, the synthesis of these nanoparticles with the desired size and functionalities poses considerable challenges. Over time, researchers have strived to optimize the synthetic route, particularly by developing greener approaches that minimize environmental impact. By reducing hazardous chemicals, energy consumption, and waste generation, these greener synthesis methods have become an important focus in the field. This review aims to provide a comprehensive analysis of the various synthetic approaches available for different types of SiNPs. Starting from the Stöber' method, we analyze other methods as well to synthesis different types of SiNPs including mesoporous, core-shell and functionalized nanoparticles. With increasing concerns with the chemical methods associated for environmental issues, we aim to assist readers in identifying suitable greener synthesis methods tailored to their specific requirements. By highlighting the advancements in reaction time optimization, waste reduction, and environmentally friendly precursors, we offer insights into the latest techniques that contribute to greener and more sustainable SiNPs synthesis. Additionally, we briefly discuss the diverse applications of SiNPs, demonstrating their relevance and potential impact in fields such as medicine, agriculture, and cosmetics. By emphasizing the greener synthesis methods and economical aspects, this review aims to inspire researchers and industry professionals to adopt environmentally conscious practices while harnessing the immense capabilities of SiNPs.

Analysis of Silicon Quantum Dots and Serum Proteins Interactions Using Asymmetrical Flow Field-Flow Fractionation

Semiconductor nanocrystals or quantum dots (QDs) have gained significant attention in biomedical research as versatile probes for imaging, sensing, and therapies. However, the interactions between proteins and QDs, which are crucial for their use in biological applications, are not yet fully understood. Asymmetric flow field-flow fractionation (AF4) is a promising method for analyzing the interactions of proteins with QDs. This technique uses a combination of hydrodynamic and centrifugal forces to separate and fractionate particles based on their size and shape. By coupling AF4 with other techniques, such as fluorescence spectroscopy and multi-angle light scattering, it is possible to determine the binding affinity and stoichiometry of protein-QD interactions. Herein, this approach has been utilized to determine the interaction between fetal bovine serum (FBS) and silicon quantum dots (SiQDs). Unlike metal-containing conventional QDs, SiQDs are highly biocompatible and photostable in nature, making them attractive for a wide range of biomedical applications. In this study, AF4 has provided crucial information on the size and shape of the FBS/SiQD complexes, their elution profile, and their interaction with serum components in real time. The differential scanning microcalorimetric technique has also been employed to monitor the thermodynamic behavior of proteins in the presence of SiQDs. We have investigated their binding mechanisms by incubating them at temperatures below and above the protein denaturation. This study yields various significant characteristics such as their hydrodynamic radius, size distribution, and conformational behavior. The compositions of SiQD and FBS influence the size distribution of their bioconjugates; the size increases by intensifying the concentration of FBS, with their hydrodynamic radii ranging between 150 and 300 nm. The results signify that in the alliance of SiQDs to the system, there is an augmentation of the denaturation point of the proteins and hence their thermal stability, providing a more comprehensive understanding of the interactions between FBS and QDs.

Nontoxic Fluorescent Nanoprobes for Multiplexed Detection and 3D Imaging of Tumor Markers in Breast Cancer

Multiplexed fluorescent immunohistochemical analysis of breast cancer (BC) markers and high-resolution 3D immunofluorescence imaging of the tumor and its microenvironment not only facilitate making the disease prognosis and selecting effective anticancer therapy (including photodynamic therapy), but also provides information on signaling and metabolic mechanisms of carcinogenesis and helps in the search for new therapeutic targets and drugs. The characteristics of imaging nanoprobe efficiency, such as sensitivity, target affinity, depth of tissue penetration, and photostability, are determined by the properties of their components, fluorophores and capture molecules, and by the method of their conjugation. Regarding individual nanoprobe components, fluorescent nanocrystals (NCs) are widely used for optical imaging in vitro and in vivo, and single-domain antibodies (sdAbs) are well established as highly specific capture molecules in diagnostic and therapeutic applications. Moreover, the technologies of obtaining functionally active sdAb–NC conjugates with the highest possible avidity, with all sdAb molecules bound to the NC in a strictly oriented manner, provide 3D-imaging nanoprobes with strong comparative advantages. This review is aimed at highlighting the importance of an integrated approach to BC diagnosis, including the detection of biomarkers of the tumor and its microenvironment, as well as the need for their quantitative profiling and imaging of their mutual location, using advanced approaches to 3D detection in thick tissue sections. The existing approaches to 3D imaging of tumors and their microenvironment using fluorescent NCs are described, and the main comparative advantages and disadvantages of nontoxic fluorescent sdAb–NC conjugates as nanoprobes for multiplexed detection and 3D imaging of BC markers are discussed.

Fluorescent silica nanoparticles as an internal marker in fruit flies and their effects on survivorship and fertility

Tracking and differentiating small insects at the individual levels requires appropriate marking materials because of their small size. This study proposes and investigates the use of fluorescent silica nanoparticles (FSNPs) as an internal marker owing to their good optical properties and biocompatibility. FSNPs were prepared using the water-in-oil reverse microemulsion technique with Rubpy dye as a fluorophore. The obtained particles were spherical, monodispersed in nanosize and exhibited bright orange luminescence under ultraviolet (UV) light. Internal marking was accomplished in fruit flies (Drosophila melanogaster) through feeding. The result shows that the fruit flies exhibit bright luminescence in their abdomen when exposed to UV light. The marking persistence duration of FSNPs in the fruit fly bodies is longer than those of other fluorescent dyes. Fruit flies fed with FSNPs have a longer lifespan than those fed with Rubpy dye. There was no difference in fertility and negative geotaxis response among the treatment and control groups. These findings demonstrate that FSNPs can be used as an internal marker in fruit flies, and are possibly applied with other small insects with a translucent abdomen.

Surface functionalization of bamboo leave mediated synthesized SiO2 nanoparticles: Study of adsorption mechanism, isotherms and enhanced adsorption capacity for removal of Cr (VI) from aqueous solution

Green synthesis of nanoparticles (NPs) provides economic and environmental benefits as an alternative to chemical or physical methods. Furthermore, the surface properties of such NPs can be modulated by means of the functionalization with different groups making them suitable for various advanced functional applications including water pollutants removal using adsorption technique. In the present work, an eco-friendly synthesis route for nano-adsorbent SiO₂ NPs and subsequent surface modifications for enhanced adsorption capacity in removal of Cr(VI) ions from aqueous solution are reported. The green synthesis of SiO₂ NPs was carried out using simple bamboo leaves followed by surface modification with amine (A-SiO₂) and carboxylic (C-SiO₂) functional groups with aim to study the effect of functionalization on adsorption capacity. These nano-adsorbents were characterized by FTIR, SEM, XPS, BET, and zeta potential. and adsorption of Cr(VI) was studied at varying parameters i.e. NPs mass, contact time, and solution pH. The investigation shows interesting results revealing the importance of interactions between the surface functional groups on SiO₂ NPs and Cr(VI) species as well as experimental conditions for the choice of surface modifier to achieve a maximum adsorption capacity. The adsorption mechanism has been studied using Langmuir, Freundlich and Temkin adsorption isotherms. The maximum adsorption capacity has been achieved in the case of A-SiO₂ NPs which was found to 174 mg/g and much higher than that of SiO₂ and C-SiO₂ NPs attributed to the selective adsorption and pH conditions. Additionally, A-SiO₂ NPs exhibit excellent recyclability indicating their suitability for promising and long term potential applications. This study provides a novel, simple and cost-effective synthesis/surface engineering technology for producing high performance recyclable nano-adsorbents for adsorptive removal of Cr(VI).

Generating Lifetime-Enhanced Microbubbles by Decorating Shells with Silicon Quantum Nano-Dots Using a 3-Series T-Junction Microfluidic Device

Long-term stability of microbubbles is crucial to their effectiveness. Using a new microfluidic device connecting three T-junction channels of 100 μm in series, stable monodisperse SiQD-loaded bovine serum albumin (BSA) protein microbubbles down to 22.8 ± 1.4 μm in diameter were generated. Fluorescence microscopy confirmed the integration of SiQD on the microbubble surface, which retained the same morphology as those without SiQD. The microbubble diameter and stability in air were manipulated through appropriate selection of T-junction numbers, capillary diameter, liquid flow rate, and BSA and SiQD concentrations. A predictive computational model was developed from the experimental data, and the number of T-junctions was incorporated into this model as one of the variables. It was illustrated that the diameter of the monodisperse microbubbles generated can be tailored by combining up to three T-junctions in series, while the operating parameters were kept constant. Computational modeling of microbubble diameter and stability agreed with experimental data. The lifetime of microbubbles increased with increasing T-junction number and higher concentrations of BSA and SiQD. The present research sheds light on a potential new route employing SiQD and triple T-junctions to form stable, monodisperse, multi-layered, and well-characterized protein and quantum dot-loaded protein microbubbles with enhanced stability for the first time.

Magnetic Nylon 6 Nanocomposites for the Microextraction of Nucleic Acids from Biological Samples

Magnetic Fe3O4 nanoparticles (MNPs) have great potential for nucleic acid separation, detection, and delivery. MNPs are considered a valuable tool in biomedicine due to their cost-effectiveness, stability, easy surface functionalization, and the possibility of the manipulations under a magnetic field. Herein, the synthesis of magnetic nylon 6 nanocomposites (MNPs@Ny6) was investigated. Transmission electron microscopy (TEM) was used for morphology and size analysis. A new method of UV-induced immobilization of oligonucleotides on MNPs@Ny6 for nucleic acid magnetic separation was proposed. MNPs@Ny6 shows a high oligonucleotide binding capacity of 2.2 nmol/mg with 73.3% loading efficiency. The proposed system has been applied to analyze model mixtures of target RNA on the total yeast RNA background. The RNA target isolation efficiency was 60% with high specificity. The bind RNA release was 88.8% in a quantity of 0.16 nmol/mg. The total RNA capture efficiency was 53%. Considering this, the MNPs@Ny6 is an attractive candidate for nucleic acids-specific magnetic isolation.

Antenna effect of pyridoxal phosphate on the fluorescence of mitoxantrone-silicon nanoparticles and its application in alkaline phosphatase assay

As a kind of sensing and imaging fluorescent probe with the merit of low toxicity, good stability, and environment-friendly, silicon nanoparticles (SiNPs) are currently attracting extensive research. In this work, we obtained mitoxantrone-SiNPs (MXT-SiNPs) with green emission by one-pot synthesis under mild temperature condition. The antenna based on pyridoxal phosphate (PLP) was designed for light-harvesting to enhance the luminescence of MXT-SiNPs and to establish a novel sensing strategy for alkaline phosphatase (ALP). PLP transfers the absorbed photon energy to MXT-SiNPs by forming Schiff base. When PLP is dephosphorized by ALP, the released free hydroxyl group reacts with aldehyde group to form internal hemiacetal, which leads to the failure of Schiff base formation. Based on the relationship between antenna formation ability and PLP hydrolysis degree, the activity of ALP can be measured. A good linear relationship was obtained from 0.2 to 3.0 U/L, with a limit of detection of 0.06 U/L. Furthermore, the sensing platform was successfully used to detect ALP in human serum with recovery of 97.6-106.2%. The rational design of antenna elements for fluorescent nanomaterials can not only provide a new pathway to manipulate the luminescence, but also provide a new direction for fluorescence sensing strategy.

1D Colloidal chains: recent progress from formation to emergent properties and applications

Integrating nanoscale building blocks of low dimensionality (0D; i.e., spheres) into higher dimensional structures endows them and their corresponding materials with emergent properties non-existent or only weakly existent in the individual building blocks. Constructing 1D chains, 2D arrays and 3D superlattices using nanoparticles and colloids therefore continues to be one of the grand goals in colloid and nanomaterial science. Amongst these higher order structures, 1D colloidal chains are of particular interest, as they possess unique anisotropic properties. In recent years, the most relevant advances in 1D colloidal chain research have been made in novel synthetic methodologies and applications. In this review, we first address a comprehensive description of the research progress concerning various synthetic strategies developed to construct 1D colloidal chains. Following this, we highlight the amplified and emergent properties of the resulting materials, originating from the assembly of the individual building blocks and their collective behavior, and discuss relevant applications in advanced materials. In the discussion of synthetic strategies, properties, and applications, particular attention will be paid to overarching concepts, fresh trends, and potential areas of future research. We believe that this comprehensive review will be a driver to guide the interdisciplinary field of 1D colloidal chains, where nanomaterial synthesis, self-assembly, physical property studies, and material applications meet, to a higher level, and open up new research opportunities at the interface of classical disciplines.

Single-step acid-catalyzed synthesis of luminescent colloidal organosilica nanobeads

We present a single-step, room-temperature synthesis of fluorescent organosilica nanobeads (FOS NBs). The FOS NBs were synthesized under aqueous conditions using (3-aminopropyl)triethoxysilane (APTES) as the silicon source in the presence of L-ascorbic acid (L-AA). In the APTES/L-AA/water ternary phase, the hydrolysis and condensation reaction of APTES occurred under acidic conditions to form spherical FOS NBs with an average diameter of 426.8 nm. FOS NBs exhibit excellent colloidal stability in aqueous media. The formation of FOS NBs was complete within a 10 min reaction time, which indicates potential for large-scale mass-production synthesis of luminescent colloidal NBs. The FOS NBs exhibited blue photoluminescence (PL) under UV excitation in the absence of an additional high temperature calcination process or with the incorporation of any fluorophores. This phenomenon is attributed to the presence of carbon-containing defects, which act as luminescent centers formed by the reaction between amino groups in the APTES and L-ascorbic acid reductant. Finally, the results of a cytotoxicity test and cellular uptake experiments revealed that the FOS NBs showed potential as optical contrast agents for bioimaging.

A Novel Pd-P Nano-Alloy Supported on Functionalized Silica for Catalytic Aerobic Oxidation of Benzyl Alcohol

Catalytic aerobic oxidation of benzyl alcohol (BnOH) to benzaldehyde (PhCHO) over supported noble metal catalysts has grabbed the attention of researchers due to the critical role of PhCHO in numerous industrial syntheses. In the present study, a novel catalyst, Pd-P alloy supported on aminopropyl-functionalized mesoporous silica (NH2-SiO2), was prepared through in situ reduction and characterized by BET-BJH analysis, SEM, TEM, XRD, FTIR, TG-DTA, and XPS. Chemical properties and catalytic performance of Pd-P/NH2-SiO2 were compared with those of Pd° nanoparticles (NPs) deposited on the same support. Over Pd-P/NH2-SiO2, the BnOH conversion to PhCHO was much higher than over Pd°/NH2-SiO2, and significantly influenced by the nature of solvent, reaching 57% in toluene at 111 °C, with 63% selectivity. Using pure oxygen as an oxidant in the same conditions, the BnOH conversion increased up to 78%, with 66% selectivity. The role of phosphorous in improving the activity may consist of the strong interaction with Pd that favours metal dispersion and lowers Pd electron density.

Red-Emitting Hybrid Based on Eu3+-dbm Complex Anchored on Silica Nanoparticles Surface by Carboxylic Acid for Biomarker Application

Luminescent organic-inorganic hybrids containing lanthanides (Ln³⁺) have been prominent for applications such as luminescent bio-probes in biological assays. In this sense, a luminescent hybrid based on dense silica (SiO₂) nanospheres decorated with Eu³⁺ β-diketonate complexes using dibenzoylmethane (Hdbm) as a luminescent antenna was developed by using a hierarchical organization in four steps: (i) anchoring of 3-aminopropyltriethoxysilane (APTES) organosilane on the SiO₂ surface, (ii) formation of a carboxylic acid ligand, (iii) coordination of Eu³⁺ to the carboxylate groups and (iv) coordination of dbm^- to Eu³⁺. The hybrid structure was elucidated through the correlation of thermogravimetry, silicon nuclear magnetic resonance and photoluminescence. Results indicate that the carboxylic acid-Eu³⁺-dbm hybrid was formed on the surface of the particles with no detectable changes on their size or shape after all the four steps (average size of 32 ± 7 nm). A surface charge of -27.8 mV was achieved for the hybrid, assuring a stable suspension in aqueous media. The Eu³⁺ complex provides intense red luminescence, characteristic of Eu³⁺⁵D₀→⁷F_J electronic transitions, with an intrinsic emission quantum yield of 38%, even in an aqueous suspension. Therefore, the correlation of luminescence, structure, particle morphology and fluorescence microscopy images make the hybrid promising for application in bioimaging.

Integrating sol-gel and carbon dots chemistry for the fabrication of fluorescent hybrid organic-inorganic films

Highly fluorescent blue and green-emitting carbon dots have been designed to be integrated into sol-gel processing of hybrid organic-inorganic materials through surface modification with an organosilane, 3-(aminopropyl)triethoxysilane (APTES). The carbon dots have been synthesised using citric acid and urea as precursors; the intense fluorescence exhibited by the nanoparticles, among the highest reported in the scientific literature, has been stabilised against quenching by APTES. When the modification is carried out in an aqueous solution, it leads to the formation of silica around the C-dots and an increase of luminescence, but also to the formation of large clusters which do not allow the deposition of optically transparent films. On the contrary, when the C-dots are modified in ethanol, the APTES improves the stability in the precursor sol even if any passivating thin silica shell does not form. Hybrid films containing APTES-functionalized C-dots are transparent with no traces of C-dots aggregation and show an intense luminescence in the blue and green range.

Interfacial separation of concentrated dye mixtures from solution with environmentally compatible nitrogenous-silane nanoparticles modified with Helianthus annuus husk extract

The capacity of an adsorbent to bind and remove dye from solution greatly depends on the type of functionalization present on the nanoparticles surface, and its interaction with the dye molecules. Within this study, nitrogenous silane nanoparticles were hydrothermally synthesized resulting in the formation of rapid and highly efficient adsorbents for concentrated mixed dyes. The amorphous silane nanoparticles exhibited a monolayer based mechanism of mixed dye adsorption with removal capacities between 416.67 and 714.29 mg/g of adsorbent. Dye removal was predominantly due to the electrostatic attraction between the positively charged silane nanoparticles (13.22-8.20 mV) and the negatively charged dye molecules (-54.23 mV). Addition of H. annuus extract during synthesis resulted in three times the surface area and 10 times increased pore volume compared to the positive control. XPS analysis showed that silane treatments had various nitrogen containing functionalities at their surface responsible for binding dye. The weak colloidal stability of silane particles (13.22-8.20 mV) was disrupted following dye binding, resulting in their rapid coagulation and flocculation which facilitated the separation of bound dye molecules from solution. The suitability for environmental applications using these treatments was supported by a bacterial viability assay showing >90% cell viability in treated dye supernatants.

The synthesis of switch-off fluorescent water-stable copper nanocluster Hg2+ sensors via a simple one-pot approach by an in situ metal reduction strategy in the presence of a thiolated polymer ligand template

The fabrication of stable fluorescent copper nanoclusters (CuNCs) in aqueous media is still challenging, despite the low price and potential biomedical applications. Herein, we report a facile and efficient strategy for assembling CuNCs using multifunctional thiolated copolymers with pH and thermoresponsive features. The new nanohybrids are formed via a simple one-pot approach through the reduction of a copper salt with hydrazine in the presence of a multithiolated polymer, which provides a template during nanocluster assembly and further efficient protection against oxidation and aggregation. Furthermore, the thermo- and pH-responsive properties of the pristine copolymers endow the nanohybrids with these stimuli-responsive features. The thiol content and the macromolecular size of the polymer ligands exert strong influences on the final photophysical properties of these new hybrid luminescent nanoclusters. The existence of stable bright greenish-yellow emission in water over long periods of time, the high photostability under UV irradiation and the strong oxidation resistance toward hydrogen peroxide of the hybrid CuNCs suggest that they have great promise for nanomedicine, bioassay and nanosensor use. Furthermore, the polymeric CuNCs obtained have been successfully tested as optical switch-off sensors for the sensitive and highly selective detection of Hg2+ in the presence of other metal ions in liquid and solid states. Finally, we demonstrate the practical application of the new hybrid to Hg2+ detection in human urine.

Fluorimetric Detection of Single Pathogenic Bacterium in Milk and Sewage Water Using pH-Sensitive Fluorescent Carbon Dots and MALDI-TOF MS

The current study is focused on the application of water-soluble, fluorescent, and pH-sensitive carbon dots (CDs) as a nanoprobe for sensitive detection of pathogenic bacteria in milk and sewage water. The CDs were facilely synthesized through the controlled carbonization of sucrose using sulfuric acid and characterized through XRD, FTIR, TEM, UV-Vis Spectroscopy, and fluorescent analysis. The as-synthesized CDs were highly water-soluble, stable, and pH-sensitive fluorescent nanomaterials. The pH-related fluorescence study showed that the ratio of fluorescence intensity (Log[IF410/IF350]) changed linearly in the pH range between 4.9 and 6.9 in the Britton-Robison buffer. By determining the pH variation of the growth medium caused by the released acidic metabolites, the CDs-based ratiometric nanoprobe and MALDI-TOF mass spectrometry (MS) were used for the detection and identification of Escherichia coli O157:H7, respectively. The practical applicability of the pH-sensitive fluorescent CDs-based ratiometric nanoprobe was evaluated to detect Escherichia coli O157:H7 in real samples, i.e., milk and sewage water using agar count plate method with a limit of detection (LOD) up to 1 colony-forming unit per mL (CFU/mL).

Kinetic and spectroscopic responses of pH-sensitive nanoparticles: influence of the silica matrix

Intracellular pH sensing with fluorescent nanoparticles is an emerging topic as pH plays several roles in physiology and pathologic processes. Here, nanoparticle-sized pH sensors (diameter far below 50 nm) for fluorescence imaging have been described. Consequently, a fluorescent derivative of pH-sensitive hydroxypyrene with pK _a = 6.1 was synthesized and subsequently embedded in core and core-shell silica nanoparticles via a modified Stöber process. The detailed fluorescence spectroscopic characterization of the produced nanoparticles was carried out for retrieving information about the environment within the nanoparticle core. Several steady-state and time-resolved fluorescence spectroscopic methods hint to the screening of the probe molecule from the solvent, but it sustained interactions with hydrogen bonds similar to that of water. The incorporation of the indicator dye in the water-rich silica matrix neither changes the acidity constant nor dramatically slows down the protonation kinetics. However, cladding by another SiO₂ shell leads to the partial substitution of water and decelerating the response of the probe molecule toward pH. The sensor is capable of monitoring pH changes in a physiological range by using ratiometric fluorescence excitation with λ _ex = 405 nm and λ _ex = 488 nm, as confirmed by the confocal fluorescence imaging of intracellular nanoparticle uptake.

Classification, Synthesis, and Application of Luminescent Silica Nanoparticles: a Review

Luminescent materials are of worldwide interest because of their unique optical properties. Silica, which is transparent to light, is an ideal matrix for luminescent materials. Luminescent silica nanoparticles (LSNs) have broad applications because of their enhanced chemical and thermal stability. Silica spheres of various sizes could be synthesized by different methods to satisfy specific requirements. Diverse luminescent dyes have potential for different applications. Subject to many factors such as quenchers, their performance was not quite satisfying. This review thus discusses the development of LSNs including their classification, synthesis, and application. It is the highlight that how silica improves the properties of luminescent dye and what role silica plays in the system. Further, their applications in biology, display, and sensors are also described.

Facile synthesis of highly luminescent lithium silicate nanocrystals with varying crystal structures and morphology

The colloidal synthesis of lithium silicate nanocrystals with varying morphology, composition, crystal structures, and high intensity visible luminescence is reported.

Silica nanoparticles induce conformational changes of tau protein and oxidative stress and apoptosis in neuroblastoma cell line

The adverse effects of SiO₂ NPs on the biological systems like nervous system have not been well explored. This study aimed to evaluate the toxicity of SiO₂ NPs on the nervous system in vitro. Therefore, human tau protein and neuroblastoma cell line (SH-SY5Y) were used as targets. In this study we examined the side effects of SiO₂ NPs on tau protein structure using several techniques including CD, ANS fluorescence, UV-vis (360 nm), Congo red absorbance, TEM, and molecular dynamic. Also, the cytotoxicity effects of SiO₂ NPs against SH-SY5Y cell line were evaluated using MTT, ROS and apoptotic assays. Spectroscopic and molecular dynamic investigations indicated that natively unfolded structure of tau in the presence of SiO₂ NPs experienced a partially folded and amorphous aggregated structure. Cellular assay demonstrated that SiO₂ NPs exerted cytotoxic effect on SH-SY5Y cells through ROS accumulation and induction of apoptosis. Overall, these findings proved that SiO₂ NPs could induce adverse effects on tau structure and SH-SY5Y cell integrity. Moreover, further studies are required to elucidate the molecular mechanism of SiO₂ NPs-induced side effects in vivo.

Transition-Metal-Doped NIR-Emitting Silicon Nanocrystals

Impurity-doping in nanocrystals significantly affects their electronic properties and diversifies their applications. Herein, we report the synthesis of transition metal (Mn, Ni, Co, Cu)-doped oleophilic silicon nanocrystals (SiNCs) through hydrolysis/polymerization of triethoxysilane with acidic aqueous metal salt solutions, followed by thermal disproportionation of the resulting gel into a doped-Si/SiO2 composite that, upon HF etching and hydrosilylation with 1-n-octadecene, produces free-standing octadecyl-capped doped SiNCs (diameter≈3 to 8 nm; dopant <0.2 atom %). Metal-doping triggers a red-shift of the SiNC photoluminescence (PL) of up to 270 nm, while maintaining high PL quantum yield (26 % for Co doping).

One-pot hydrothermal synthesis of luminescent silicon-based nanoparticles for highly specific detection of oxytetracycline via ratiometric fluorescent strategy

Amino groups terminated luminescent SiNPs have been designed for ratiometric visual detection of OTC in vitro and milk samples.