Nonclassical Pathways: Accelerated Crystal Growth of Sodium Hexafluorosilicate Microrods via Nanoparticle-Assisted Processes with 0D Silicon Quantum Dots.

Nonclassical crystallization represents an innovative pathway that utilizes nanoparticles, enabling the generation of single crystals, going beyond a classical mechanism dependent on atoms, ions, or molecules. Our investigation has revealed hierarchical structures emerging via the aggregation and fusion of primary silicon quantum dots (SiQDs). In contrast to the classical ion-by-ion crystallization process, the primary SiQDs initially undergo aggregation, followed by fusion and their subsequent crystallization, leading to the ultrafast crystal growth of sodium hexafluorosilicate (SHFS) microrods with diverse morphologies. A comprehensive fluorescence microscopy study is performed to examine the mechanism of microrod formation through the primary aggregation and fusion of SiQDs at room temperature in the presence of hydrogen fluoride (HF). The different concentrations of HF play a crucial role in the formation of flower-, block-, and hexagonal-shaped SHFS microrods. However, the presence of a high-concentration HF causes a reduction in microrod size, elucidated through a range of analytical and spectroscopic techniques.

Strong coupling of hybrid states of light and matter in cavity-coupled quantum dot solids.

The formation of plasmon-exciton (plexciton) polariton is a direct consequence of strong light-matter interaction, and it happens in a semiconductor-metal hybrid system. Here the formation of plasmon-exciton polaritons was observed from an AgTe/CdTe Quantum Dot (QD) solid system in the strong coupling regime. The strong coupling was achieved by increasing the oscillator strength of the excitons by forming coupled QD solids. The anti-crossing-like behaviour indicates the strong coupling between plasmonic and excitons state in AgTe/CdTe QD solids, resulting in a maximum Rabi splitting value of 225 meV at room temperature. The formation of this hybrid state of matter and its dynamics were studied through absorption, photoluminescence, and femtosecond transient studies.

Induced UV photon sensing properties in narrow bandgap CdTe quantum dots through controlling hot electron dynamics.

Mn-doped CdTe (Mn-CdTe) quantum dot (QD) as well as quantum dot solid (QD solid) nanostructures are formed and the established structures are confirmed through HR-TEM analysis. The dynamics of charge carriers in both doped & undoped QD and QD solid structures were investigated by transient absorption (TA) spectroscopy. A slow band edge bleach recovery is obtained for Mn-doped CdTe QD and CdTe QD solid systems at room temperature. Additionally, a blue shifted broad bleach behaviour is identified for the Mn-CdTe QD solid system, which is attributed to hot exciton formation in the solid upon photoexcitation with a higher photon energy than the band gap energy (hν > Eg). This noteworthy process of generation of hot excitons and slow charge recombination occurs by means of a synergetic action of the Mn dopant in the host CdTe QD solid system as well as the extended electronic wave function between the coupled QD solid. Apart from the Mn-assisted delayed relaxation of hot electrons in the QD solid, a suppression in dark current as well as a high ION/IOFF ratio of 3203.12 at 1 V is observed in the Mn-CdTe QD-solid based photosensitized device in the visible region. Furthermore, we were able to improve the UV photon harvesting property in a narrow band gap Mn-CdTe QD solid through reducing the higher excited carrier's energy losses.

Correction: Induced UV photon sensing properties in narrow bandgap CdTe quantum dots through controlling hot electron dynamics.

Correction for 'Induced UV photon sensing properties in narrow bandgap CdTe quantum dots through controlling hot electron dynamics' by Thankappan Thrupthika et al., Phys. Chem. Chem. Phys., 2023, https://doi.org/10.1039/d3cp02424e.

In vivo evaluation of Nano-palladium toxicity on larval stages and adult of zebrafish (Danio rerio).

The existence and usage of nano-sized palladium (nano-Pd) as catalytic promoters among industries and researchers have been laid a way to explore the release of nano-Pd particles into the aquatic environment, bio-accumulating in living organisms. However, the data on fate and toxicity in response to nano-Pd on aquatic organisms are very limited. Herein, we report the concentration-specific toxicity of nano-Pd in zebrafish (Danio rerio). Nano-Pd was synthesized and characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Dynamic Light Scattering (DLS) and Zeta potential. To determine the in vivo toxicity of nano-Pd, the 96 hpf larvae and the adult zebrafish were treated with two (22 and 0.4 ng/L) environmental relevant concentrations. High doses of nano-Pd influenced the hatching rate, embryo survival, heartbeat and teratological anomalies in the 96 hpf larvae. Reactive oxygen species (ROS) and apoptosis were also influenced by nano-Pd exposure while the acetylcholinesterase (AChE) activity was declined in a dose dependent manner. In long-term exposure (42 days), the adult fish showed erratic movements in swimming pattern inhibiting the AChE activity in both the concentrations of brain and liver. The antioxidant enzyme activity such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione reductase (GR) and lipid peroxidation (LPO), showed a significant change (P < 0.05) indicating that oxidative stress was induced by nano-Pd. Similarly, nano-Pd also induced histopathological lesions in gill, liver and brain providing an insight of fate and toxicity of nano-Pd in the aquatic environment. Our study contributes a significant mechanism to understand the toxicity concern of nano-Pd in the aquatic environment.

Aggregation induced emission behavior in oleylamine acetone system and its application to get improved photocurrent from In2S3 quantum dots.

Blue emission giving nanoscale molecular clusters of Oleylamine-Acetone system was formed by an aging assisted hydrogen bond formation between the interacting molecular systems, at room temperature. The as-formed nanoscale molecular clusters were found to be self-assembled into flower-like aggregates and shifted the emission wavelength to red colour depicting an exciton delocalization in the aggregate system. Interestingly aging process has also produced imine type binding between Oleylamine and Acetone due to the condensation reaction. The experimental conditions and formation mechanism of hydrogen bond assisted Oleylamine-Acetone molecular aggregates and imine bond assisted Oleylamine-Acetone is elaborated in this paper in a systematic experimental approach with suitable theory. Finally we have introduced this Acetone assisted aging process in In2S3 QD system prepared with Oleylamine as functional molecules. It was found that the aging process has detached Oleylamine from QD surface and as a consequence In2S3 QD embedded Oleylamine-Acetone aggregates was obtained. When this In2S3 QD embedded molecular cluster system was used as an active layer in a photo conductor device then a maximum photo current value of the order of milli Ampere was obtained. The surfactant molecules normally inhibit the charge transport between QD systems and as a result it is always problematic to have the functional molecules in the QD based transport devices. Our approach has a solution to this problem and the present paper discusses the outcome of the results in detail.

Insight into the photophysics of strong dual emission (blue & green) producing graphene quantum dot clusters and their application towards selective and sensitive detection of trace level Fe3+ and Cr6+ ions.

Graphene-nanostructured systems, such as graphene quantum dots (GQDs), are well known for their interesting light-emitting characteristics and are being applied to a variety of luminescence-based applications. The emission properties of GQDs are complex. Therefore, understanding the science of the photophysics of coupled quantum systems (like quantum clusters) is still challenging. In this regard, we have successfully prepared two different types of GQD clusters, and explored their photophysical properties in detail. By co-relating the structure and photophysics, it was possible to understand the emission behavior of the cluster in detail. This gave new insight into understanding the clustering effect on the emission behaviour. The results clearly indicated that although GQDs are well connected, the local discontinuity in the structure prohibits the dynamics of photoexcited charge carriers going from one domain to another. Therefore, an excitation-sensitive dual emission was possible. Emission yield values of about 18% each were recorded at the blue and green emission wavelengths at a particular excitation energy. This meant that the choice of emission color was decided by the excitation energy. Through systematic analysis, it was found that both intrinsic and extrinsic effects contributed to the blue emission, whereas only the intrinsic effect contributed to the green emission. These excitation-sensitive dual emissive GQD clusters were then used to sense Fe3+ and Cr6+ ions in the nanomolar range. While the Cr6+ ions were able to quench both blue and green emissions, the Fe3+ ions quenched blue emission only. The insensitivity of the Fe3+ ions in the quenching of the green emission was also understood through quantum chemical calculations.

Surface and morphology analyses, and voltammetry studies for electrochemical determination of cerium(iii) using a graphene nanobud-modified-carbon felt electrode in acidic buffer solution (pH 4.0 ± 0.05).

Trace determination of radioactive waste, especially Ce3+, by electrochemical methods has rarely been attempted. Ce3+ is (i) a fluorescence quencher, (ii) an antiferromagnet, and (iii) a superconductor, and it has been incorporated into fast scintillators, LED phosphors, and fluorescent lamps. Although Ce3+ has been utilized in many industries due to its specific properties, it causes severe health problems to human beings because of its toxicity. Nanomaterials with fascinating electrical properties can play a vital role in the fabrication of a sensor device to detect the analyte of interest. In the present study, surfactant-free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) with nanobud (NB) morphology were utilized for the determination of Ce3+ through electrochemical studies. The working electrode, graphene nanobud (GNB)-modified-carbon felt (CF), was developed by a simple drop-coating method for the sensitive detection of Ce3+ in acetate buffer solution (ABS, pH 4.0 ± 0.05) at a scan rate of 50 mV s-1 using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. CV and DPV studies validated the existence of distinctive peaks at approximately +0.20 and +0.93 V (vs. SCE), respectively, with a limit of detection of approximately 2.60 µM. Furthermore, electrochemical studies revealed that the GNB-modified-CF electrode was (i) stable even after fifteen cycles, (ii) reproducible, (iii) selective towards Ce3+, (iv) strongly pH-dependent, and (v) favored Ce3+ sensing only at pH 4.0 ± 0.05. Impedance spectroscopy results indicated that the GNB-modified-CF electrode was more conductive (1.38 × 10-4 S m-1) and exhibited more rapid electron transfer than bare CF, which agrees with the attained Randles equivalent circuit. Microscopy (AFM, FE-SEM, and HR-TEM), spectroscopy (XPS and Raman), XRD, and energy-dispersive X-ray (EDX) analyses of the GNB-modified-CF electrode confirmed the adsorption of Ce3+ onto the electrode surface and the size of the electrode material. Ce3+ nanobuds increased from 35-40 to 50-55 nm without changing their morphology. The obtained results provide an insight into the determination of Ce3+ to develop an electrochemical device with low sensitivity.

Highly Responsive Ultraviolet Sensor Based on ZnS Quantum Dot Solid with Enhanced Photocurrent.

Detection of visible blind UV radiation is not only interesting but also of technologically important. Herein, we demonstrate the efficient detection of UV radiation by using cluster like ZnS quantum dot solid nanostructures prepared by simple reflux condensation technique. The short-chain ligand 3-mercaptopropionic acid (MPA) involved in the synthesis lead to the cluster like formation of ZnS quantum dots into solids upon prolonged synthesis conditions. The ZnS QD solid formation resulted in the strong delocalization of electronic wave function between the neighboring quantum dots. It increases the photocurrent value, which can be further confirmed by the decrease in the average lifetime values from 64 to 4.6 ns upon ZnS cluster like QD solid formation from ZnS QDs. The ZnS quantum dot solid based UV sensor shows good photocurrent response and a maximum responsivity of 0.31 (A/W) at a wavelength of 390 nm, is not only competitive when compared with previous reports but also better than ZnS and metal oxide-based photodetectors. The device exhibits a high current value under low-intensity UV light source and an on/off ratio of IUV/Idark = 413 at zero biasing voltage with a fast response. Further, photocurrent device has been constructed using ZnS quantum dot solid nanostructures with graphene hybrids as an active layer to improve the enhancement of photoresponsivity.

Graphene Nanobuds: A New Second-Generation Phosgene Sensor with Ultralow Detection Limit in Aqueous Solution.

Selective and sensitive detection of highly toxic chemicals by a suitable, fast, inexpensive, and trustworthy method is vital due to its serious health threats to humankind and breach of public security caused by unexpected terrorist attacks and industrial accidents. Phosgene or carbonyl dichloride is widely employed in many chemical industries and pharmaceuticals, and in pesticide production, which is extremely toxic by severe (short-term) inhalation exposure. Because of the non-existence of a phosgene sensor in aqueous solution and the immense emphasis gained by nanomaterials, especially carbonaceous materials, augmented attention has been given to the development of a fluorophore-functionalized carbon-based method to detect this noxious substance. In this study, surfactant free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) were prepared to detect phosgene in aqueous solution. The FESEM (field emission scanning electron microscopy) and HRTEM (high-resolution transmission electron microscopy) analyses confirm the as-prepared DAN-GQD morphology as nanobuds (NBs) with an average diameter of ca. 35-40 nm. The crystalline nature, elemental composition, and chemical state of DAN-GQDs were analyzed by standard physiochemical techniques. The edge-termination at the carboxyl functional group of GQDs with DAN was examined by XPS, Raman, FT-IR, and 1H NMR spectroscopy analyses. The aqueous solution of DAN-GQDs (4.89 × 10-9 M) exhibits a strong emission peak at 423 nm upon excitation at 328 nm. The addition of the phosgene molecule (0 → 88 µL) quenches the initial fluorescence intensity of DAN-GQDs (ΦF 53.6 → 34.6%) through the formation of a stable six-membered cyclized product. The DAN-GQDs displayed excellent selectivity and sensitivity for phosgene ( Ka = 3.84 × 102 M-1 and LoD (limit of detection) = 2.26 ppb) over other competing toxic pollutants in water. The time-resolved fluorescence analysis confirms that the quenching of DAN-GQDs follows nonradiative relaxation of excited electrons. Furthermore, bioimaging experiments of phosgene in living human breast cancer (HeLa) cells and cell viability test successfully demonstrated the practicability of DAN-GQDs.

Iron and iron oxide nanoparticles are highly toxic to Culex quinquefasciatus with little non-target effects on larvivorous fishes.

The control of filariasis vectors has been enhanced in several areas, but there are main challenges, including increasing resistance to insecticides and lack of cheap and eco-friendly products. The toxicity of iron (Fe0) and iron oxide (Fe2O3) nanoparticles has been scarcely investigated yet. We studied the larvicidal and pupicidal activity of Fe0 and Fe2O3 nanoparticles against Culex quinquefasciatus. Fe0 and Fe2O3 nanoparticles produced by green (using a Ficus natalensis aqueous extract) and chemical nanosynthesis, respectively, were analyzed by UV-Vis spectrophotometry, FT-IR spectroscopy, XRD analysis, SEM, and EDX assays. In larvicidal and pupicidal experiments on Cx. quinquefasciatus, LC50 of Fe0 nanoparticles ranged from 20.9 (I instar larvae) to 43.7 ppm (pupae) and from 4.5 (I) to 22.1 ppm (pupae) for Fe2O3 nanoparticles synthesized chemically. Furthermore, the predation efficiency of the guppy fish, Poecilia reticulata, after a single treatment with sub-lethal doses of Fe0 and Fe2O3 nanoparticles was magnified. Overall, this work provides new insights about the toxicity of Fe0 and Fe2O3 nanoparticles against mosquito vectors; we suggested that green and chemical fabricated nano-iron may be considered to develop novel and effective pesticides.

Graphene Quantum Dot Solid Sheets: Strong blue-light-emitting & photocurrent-producing band-gap-opened nanostructures.

Graphene has been studied intensively in opto-electronics, and its transport properties are well established. However, efforts to induce intrinsic optical properties are still in progress. Herein, we report the production of micron-sized sheets by interconnecting graphene quantum dots (GQDs), which are termed 'GQD solid sheets', with intrinsic absorption and emission properties. Since a GQD solid sheet is an interconnected QD system, it possesses the optical properties of GQDs. Metal atoms that interconnect the GQDs in the bottom-up hydrothermal growth process, induce the semiconducting behaviour in the GQD solid sheets. X-ray absorption measurements and quantum chemical calculations provide clear evidence for the metal-mediated growth process. The as-grown graphene quantum dot solids undergo a Forster Resonance Energy Transfer (FRET) interaction with GQDs to exhibit an unconventional 36% photoluminescence (PL) quantum yield in the blue region at 440 nm. A high-magnitude photocurrent was also induced in graphene quantum dot solid sheets by the energy transfer process.

Optical detection of CA 15.3 breast cancer antigen using CdS quantum dot.

The present study focus on optical sensing of breast cancer antigen 15.3 (CA 15.3) using cadmium sulphide quantum dot (CdS-QD) in saline and serum samples spiked with antigen. The surface of CdS-QD was modified by cysteamine capping followed by tagging of CA 15.3 antibody. The samples were characterised using UV-visible absorption spectroscopy (UV-VIS Spectroscopy), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM) attached with energy-dispersive X-ray spectroscopy, phase contrast inverted epi-fluorescence microscopy and photoluminescence (PL) spectrophotometry (EDS). The CdS-QD showed a mean diameter of 3.02 ± 0.6 nm. The complex formed after antigen-antibody interaction resulted in distinguishable optical and fluorescence intensity with respect to varying concentration of antigen. The PL study revealed that CA 15.3 antibody labelled CdS QD can detect CA 15.3 tumour marker even at very low concentration of 0.002 KU/L with a constant response time of 15 min. This study clearly indicates that detection of CA 15.3 at low concentration is possible using surface modified CdS QD in serum samples and can find immense applications in biosensor development for detection of breast cancer marker similar to various automated detection kits available in market.

Magnetic nanoparticles are highly toxic to chloroquine-resistant Plasmodium falciparum, dengue virus (DEN-2), and their mosquito vectors.

A main challenge in parasitology is the development of reliable tools to prevent or treat mosquito-borne diseases. We investigated the toxicity of magnetic nanoparticles (MNP) produced by Magnetospirillum gryphiswaldense (strain MSR-1) on chloroquine-resistant (CQ-r) and sensitive (CQ-s) Plasmodium falciparum, dengue virus (DEN-2), and two of their main vectors, Anopheles stephensi and Aedes aegypti, respectively. MNP were studied by Fourier-transform infrared spectroscopy and transmission electron microscopy. They were toxic to larvae and pupae of An. stephensi, LC50 ranged from 2.563 ppm (1st instar larva) to 6.430 ppm (pupa), and Ae. aegypti, LC50 ranged from 3.231 ppm (1st instar larva) to 7.545 ppm (pupa). MNP IC50 on P. falciparum were 83.32 µg ml-1 (CQ-s) and 87.47 µg ml-1 (CQ-r). However, the in vivo efficacy of MNP on Plasmodium berghei was low if compared to CQ-based treatments. Moderate cytotoxicity was detected on Vero cells post-treatment with MNP doses lower than 4 µg ml-1. MNP evaluated at 2-8 µg ml-1 inhibited DEN-2 replication inhibiting the expression of the envelope (E) protein. In conclusion, our findings represent the first report about the use of MNP in medical and veterinary entomology, proposing them as suitable materials to develop reliable tools to combat mosquito-borne diseases.

Carbon and silver nanoparticles in the fight against the filariasis vector Culex quinquefasciatus: genotoxicity and impact on behavioral traits of non-target aquatic organisms.

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. The Culex genus, with special reference to Culex quinquefasciatus, comprises the most common vectors of filariasis across urban and semi-urban areas of Asia. In recent years, important efforts have been conducted to propose green-synthesized nanoparticles as a valuable alternative to synthetic insecticides. However, the mosquitocidal potential of carbon nanoparticles has been scarcely investigated. In this study, the larvicidal and pupicidal activity of carbon nanoparticle (CNP) and silver nanoparticle (AgNP) was tested against Cx. quinquefasciatus. UV-Vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, and Raman analysis confirmed the rapid and cheap synthesis of carbon and silver nanoparticles. In laboratory assays, LC50 (lethal concentration that kills 50 % of the exposed organisms) values ranged from 8.752 ppm (first-instar larvae) to 18.676 ppm (pupae) for silver nanoparticles and from 6.373 ppm (first-instar larvae) to 14.849 ppm (pupae) for carbon nanoparticles. The predation efficiency of the water bug Lethocerus indicus after a single treatment with low doses of silver and carbon nanoparticles was not reduced. Moderate evidence of genotoxic effects induced by exposure to carbon nanoparticles was found on non-target goldfish, Carassius auratus. Lastly, the plant extract used for silver nanosynthesis was tested for 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity. Overall, our results pointed out that AgNP and CNP can be a candidate for effective tools to reduce larval and pupal populations of filariasis vectors, with reduced genotoxicity and impact on behavioral traits of other aquatic organisms sharing the same ecological niche of Cx. quinquefasciatus.