Current Nanoscience (v.12, #3)

Meet Our Editorial Board Member: by Anna Gina Perri (275-275).

Silica Optical Fibers Doped with Nanoparticles for Fiber Lasers and Broadband Sources by Ivan Kasik, Pavel Peterka, Jan Mrazek, Pavel Honzatko (277-290).
We present a review on recent progress in the research and development of nanoparticlecontaining optical fibers for high-power fiber lasers, amplifiers, and ASE sources. Attention has been focused on rare-earth-doped silica fibers with nanoparticles in the core. Progress in materials, technologies, characterization techniques, and achievements has been summarized. Materials of active fibers based on yttrium-aluminium silicates, mullite, protoenstatite, and phosphates doped with Er3+, Yb 3+, Eu3+, and Tm3+ have been reviewed. The material research in this field has been systematically investigated by research groups from ORC Southampton, CGCRI Kolkata, LPMC Nice together with CNR-IOM-OGG Grenoble, nLIGHT (formerly Liekki), and IPE Prague since 2007. The best slope efficiency achieved with Yb -doped nanoparticle-containing fiber was in the range of 70-80 %.

Background: The physics of graphene, the most recently discovered allotrope of carbon, is currently one of the most extensively studied branches of condensed-matter science. Graphene has attracted great attention of the photonics community in the last years. Thanks to its unique optical properties, like broadband absorption, ultrashort recovery time and large modulation depth, it is currently widely used as universal saturable absorber for mode-locking of fiber lasers operating at different wavelengths.
Methods: The paper summarizes the most prominent recent achievements in the field of graphenebased mode-locked fiber lasers. The unique optical properties of graphene are also discussed. The recent experimental results reported in the literature are described and compared.
Results: The historically first graphene-based fiber lasers were developed in 2009 independently by the groups from Singapore and United Kingdom. Shortly after those reports, a number of papers appeared, demonstrating novel concepts of ultrafast lasers utilizing various forms of graphene, most popularly epitaxially grown and exfoliated (mechanically or in liquid phase). Unique nonlinear optical properties of graphene allowed to achieve many outstanding results and revolutionize the field of ultrafast laser science. Fiber lasers operating at different wavelengths, ranging from 1 to 2 µm were demonstrated, with pulse durations at the level of femtoseconds.
Conclusion: The recent most important advances in the field of ultrafast lasers utilizing graphene have been summarized. Thanks to its unique nonlinear optical properties, graphene has revolutionized the field mode-locked, ultrashort-pulsed fiber lasers. Graphene-based saturable absorbers might be developed in various techniques and they constitute a low-cost and robust alternative to semiconductor-based saturable absorbers. The ongoing research on graphene will surely lead to another, extremely interesting photonics applications of this material in the next years.

Background: Pulsed fiber lasers operating near 1900 nm are becoming emerging laser sources for scientific and industrial applications, because of their unique advantages in terms of eye-safe wavelength, and high absorption in greenhouse gases, liquid water, and most polycarbonate materials. We develop new nanoengineering double-clad Thulium-Ytterbium co-doped fiber (TYDF) to provide an efficient lasing at 1950 nm region based on energy transfer from Ytterbium to Thulium ion. The performance of the TYDF is investigated for both continuous wave (CW) and pulse laser operations.
Methods: The TYDF is fabricated using a Modified Chemical Vapor Deposition (MCVD) process in conjunction with solution doping technique. The lasing characteristic of the TYDF laser (TYDFL) is investigated for both linear and ring configurations. The pulse generations are demonstrated using various passive saturable absorbers (SAs) such multiwalled carbon nanotubes (MWCNTs) and graphene oxide.
Results: With a linear configuration, the TYDFL operates at center wavelength of 1936.4 nm, 1958.6 nm and 1967.5 nm at gain medium lengths of 5 m, 10 m and 15 m, respectively. The proposed laser produces the highest efficiency of 9 .9 % at 10 m long TYDF and the lowest threshold pump power of 400 mW at a longer TYDF length of 15 m. The Q-switched laser operates at 1960 nm region is achieved by exploiting a MWCNTs embedded in polymer composite film as a SA. The proposed TYDFL generates a stable pulse train with repetition rates and pulse widths ranging from 18.9 to 35.1 kHz and 7.94 to 1.52 µs, respectively by varying the multimode 980 nm pump power from 440 mW to 528 mW. The maximum pulse energy of 11.2 nJ is obtained at the pump power of 512 mW. A higher performance Q switching is expected to be achieved with the optimization of the laser cavity and SA. A mode-locked TYDFL is also demonstrated using a graphene oxide (GO) based SA. The laser operates at 1942.0 nm with a threshold pump power as low as 1.8 W, a repetition rate of 22.32 MHz and calculated pulse duration of 1.1 ns.
Conclusion: The developed TYDF is capable for use in developing both CW and pulsed fiber laser in conjunction with cladding pumping technique.

Strong and Broad Visible Emission of Bismuth Doped Nano-Phase Separated Yttria-alumina-silica Optical Fibers by Arindam Halder, Shyamal K. Bhadra, Sandip Bysakh, Mukul C. Paul, Shyamal Das (309-315).
Background: Bismuth doped optical fibers (BDFs) have potential application in the area of broadband VIS and NIR luminescence in the range from 350-700 nm and 1100 to 1600 nm without presence of any rare-earth elements. Such fibers are studied intensively and used successfully in fiber amplification and lasing particularly in NIR region where no emission from any rare-earths are obtained. They have found that proper modeling for spectral behavior of Bi doped glasses and fibers, is still not available due to unpredictable oxidation states of Bi. Therefore there is scope for detail study for designing and fabricating BDFs with well organized spectral characteristics due to its long interaction length.
Methods: Bi doped nano-phase separated yttria-alumino-silica (YAS) glass optical fibers are fabricated using modified chemical vapour deposition (MCVD) associated with Sloution doping (SD) technique. The micro-structures of the core of perform and fiber samples are analyzed by TEM along with electron diffraction (ED) using thin film sampling technique. The concentration distributions of the dopants in core are analysed by EPMA. Core refractive index (RI) profile is generated using preform analyzer model: PKL 2600 of Photon Kinetics. Using the measured RI of the core numerical aperture (NA) of preforms is calculated. The absorption spectra of BDFs are measured by cutback method at room temperature to avoid external interference. Photoluminescence spectra (PL) of BDFs in VIS region are obtained by FLS920 spectrometer (Edinburg Instrument) at room temperature using ~30 cm long BDFs at 532 nm excitation of 184 mW.
Results: TEM images and ED patterns suggest that the core glasses are composed of amorphous nano-phase separated particles of size around 2-3 nm which are the Bi rich zones in the core. EPMA data show a uniform distribution of dopants within core. Absorption bands for bismuth active centres (BACs) appear mainly at ~515 nm, ~690 nm along with weak bands at ~800 nm, ~960nm and ~1200 nm and observe an overlapping zone within 400-1150 nm regime. Using Gaussian multi-peak fit technique we deconvolute them. The deconvoluted absorption bands are ~480, ~525, ~565, ~675, ~810, ~970 and ~1200 nm. The presence of multiple absorbance suggest the presence of multiple oxidation state of bismuth basically Bi0, Bi+, Bi2+ in the doped core glass. A schematic energy diagram is proposed based on the deconvoluted absorption bands. Using this diagram, the emission band, within 520 to 840 nm under 532 nm excitation, is explained.
Conclusion: Fabrication process of nano phase separated Bi-YAS optical fibers through MCVD assisted with SD technique is discussed. Phase separation of core glass is analyzed by TEM. Almost uniform dopant distribution in the core obtained through EPMA analysis. Different absorption bands of Bi active centres at VIS to NIR have been identified using suitable Gaussian multi-peaks fitting technique. The analyses confirm the presence of multiple oxidation states of Bi into the fabricated BDFs. Intense broad PL from 520 nm to 840 nm are observed under 532 nm pumping. This unique feature would be helpful for fabricating wavelength tunable broadband fiber laser source from VIS to NIR region.

Microwave-assisted Synthesis of Semiconductor Nanomaterials for Energy Storage by Haipeng Chu, Xinjuan Liu, Lengyuan Niu, Can Li, Yin Yan Gong, Shiqiang Li, Chang Q. Sun (317-323).
Semiconductor nanostructure has attracted tremendous attention due to its potential in electrochemical energy storage systems. The energy capacity is related to the properties of electrode materials. In this treatise, we will survey the recent advancement of the semiconductor nanostructures synthesized by microwave assisted method for electrode materials in electrochemical energy storage, and these nanostructures are found to show the improved electrochemical performance compared with the traditional synthesized methods.

Effect of Size and Dimensionality on the Band Gap and Conductivity of InAs, PbS, Ge, and Bi2S3 Nanostructured Semiconductors by Jianwei Li, Xinsheng Zhao, Dan Li, Xuejun Zheng, Xuexian Yang, Shulei Chou, Zhe Zhu (324-329).
The band gap and conductivity of a nano-semiconductor are tunable with the specimen size and dimensionality, and related mechanisms are under debating. From the perspective of bond orderlength- strength correlation, we have developed analytical expressions for investigating size- and dimensionality- induced change of the band gap, charge carrier concentration and conductivity of InAs, PbS, Ge, and Bi2S3 nano-semiconductor. Consistency in theoretical predictions, experimental observations, and numerical calculations clarified that size and dimensionality dependent these properties arise from surface strain and the associated quantum trap of binding energy. The surface-to-volume ratio is a key factor, which dominates size and dimensionality dependency.

Impact of Solvent Additive on Morphology of High-Efficiency Ternary Blend Solar Cell by Hui Lin, Minxia Shang, Yiran Li, Xinge Yu, Xu Ye, Lei Zhang, Quan Jiang (330-335).
Background: It is well known the PTB7:PC71BM based photovoltaic cells have drawn great attention because the devices now hold the record in PSC performance. However, the crystallinity level of the used materials was reported very low, and this was tested with X-ray diffraction. It was reported that crystalline portions of the component enable a high absorption and a balanced charge transportation. As regards the phenomenon, the impact of the additive 1,8-diiodooctane (DIO) on the device performance has been reported in many references. In the work, the impact of solvent additive DIO, on the morphology formation and performance of PTB7:PC71BM:F8BT (poly[(9,9-di-noctylfluorenyl- 2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)]) ternary PSCs was investigated.
Methods: Researches related to ternary PSCs were reviewed, and many repeatable experiments have been done. To analyze the effect of DIO on the PTB7:PC71BM:F8BT based ternary cells, we did many measurements such as absorption spectral, PL spectral, device performance, X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM).
Results: It was found that the additive plays an important role in controlling the active layers morphology of the ternary devices. When 3% described solvent additive was added to solvent CB, an increasing nearly 36% in JSC and a relatively modest 41% gain in the FF were found, which resulting in a nearly doubling of the PCE. In order to analyze the influence of additive on the device performance, morphology characterization of PTB7:PC71BM:F8BT ternary layers was elucidated using AFM and energy transport progress of the devices was probed from photoluminescence spectra.
Conclusion: In summary, we have successfully constructed the polymer ternary BHJ devices based on PTB7:PC71BM:F8BT with a nearly doubling of the PCE compared to CB fabricated ternary devices. By analyzing the absorption spectral, surface morphology, energy transfer progress and external quantum efficiency, we found that DIO as solvent additive can favor the charge separation into the charge transfer state after exciton dissociation. In more detail, an effective morphology in CB+DIO film can be obtained that provides a plentiful interfacial area for charge generation and a balanced percolation way for charge transfer, which resulting in a nearly doubling of the PCE. This study provides method to improve morphology of active films, and thus improve the performance for ternary PSCs.

Electrospun Fe2O3-carbon Composite Nanofibers as Anode Materials for Sodium-Ion Batteries by Xiaoxia Yang, Conglong Fu, Ting Lu, Zhuo Sun, Daniel H.C. Chua (336-340).
Background: With the increasing demand for large scale energy storage, people pay more and more attention on the development of sodium-ion batteries (SIBs) because of its low cost and abundance resource. This paper provides a new kind of anode material with satisfied electrical performance for SIBs.
Methods: Fe2O3-carbon composite nanofibers (FeCNFs) were synthesized through an uncomplicated and meliorable electrospinning process followed by calcination. The obtained FeCNFs were applied as anode materials for sodium-ion batteries.
Results: The FeCNFs SIBs show excellent performance. At a current density of 50 mA g-1, a high reversible capacity of 606 mA h g-1 is achieved. Moreover, an ideal reversible capacity of 167 mAh g-1 is achieved even at a current density of 500 mA g-1, demonstrating good rate capability of FeCNFs.
Conclusion: As compared with pure carbon nanofibers (CNFs), the capacity and rate capability of FeCNFs are drastically improved due to the homogeneous dispersed Fe2O3 nanoparticles on the surface of carbon nanofibers. Such a structure prevents the aggregation of Fe2O3 nanoparticles, maintains the structure integrity and thus enhances the electrochemical performance.

A Facile Synthesis of Flower-shaped ZnO/Reduced Graphene Oxide Microsphere Composites for Photocatalytic Degradation of Methyl Orange by Guang Zhu, Liangwei Chen, Qiang Wei, Peijun Guo, Xuelian Li, Wenqi Wang, Peng Luo, Hongyan Wang, Li Zhang (341-346).
Flower-shaped ZnO/reduced graphene oxide (RGO) microsphere composites were successfully fabricated via a facile hydrothermal treatment of the aqueous solution containing graphene oxide and ZnO microspheres, and their photocatalytic performance in degradation of methyl orange (MO) was investigated. The results indicated that ZnO/RGO microsphere composites with 3 wt.% GO achieves a maximum MO degradation efficiency of 88% under ultraviolet light irradiation for 140 min, compared with pure ZnO microspheres (78%). The improved photocatalytic performance can be attributed to the suppression of charge carriers recombination resulting from the interaction between ZnO and RGO.

Smart Biodegradable Nanoparticulate Materials: Poly-lactide-co-glycolide Functionalization with Selected Peptides by Barbara Colzani, Marco Biagiotti, Giovanna Speranza, Rossella Dorati, Tiziana Modena, Bice Conti, Corrado Tomasi, Ida Genta (347-356).
Background: Smart nanoparticulate materials, namely tailored nanoparticles (NPs) with specific surface functionality, have recently attracted attention as useful tool for time- and site-specific drug delivery. Specifically, polymeric nanoparticles (NPs) can be chemically functionalized with different chemical entities, i.e. peptides, that selectively recognize biological substrates in vivo and target drug release. Divergent and very complex strategies can be pursued in order to obtain peptidedecorated NPs.
Methods: A simple method was suggested for direct functionalization of poly-lactide-co-glicolide (PLGA) with small peptides. A solid-phase peptide synthesis was used to obtain a dodecapeptide (GE11) and a smaller tetrapeptide (FQPV). FQPV- and GE11-PLGA conjugates were obtained by optimized carbodiimide chemistry. Nanoprecipitation and solvent extraction/evaporation methods were purpose-built in order to prepare FQPV-PLGA NPs. NPs were characterized in terms of size, surface charge and adsorbed peptide amount; ex-vivo cytotoxicity studies were performed on FQPV-PLA NPs using adult fibroblasts.
Results: Custom GE11, recently known as efficient Epidermal Growth Factor Receptor targeting agent, and FQPV, used as model peptide, were synthesized by solid-phase peptide synthesis achieving good purity (95%) and satisfactory process yields (70-85%). Then, FQPV- and GE11-PLGA conjugates were obtained by optimized carbodiimide chemistry achieving an high degree of functionalization (> 85%). Aware of different physico-chemical properties of peptide-PLGA conjugates with respect to plain PLGA, two different NPs preparation techniques, nanoprecipitation and solvent extraction/ evaporation methods, were purpose-built in order to prepare FQPV-PLGA NPs. Both methods revealed suitable to obtain NPs with proper dimensions for the parenteral administration (< 250nm), narrow size distribution (P.I. about 0.1), good morphological features and negative charge (about -20mV). A peptide adsorption protocol onto NPs was considered as additional strategy to increase peptide expression on NPs surface aimed at improving the targeting effectiveness. A Design of Experiment approach (DoE) has been successfully applied to the more versatile solvent extraction/ evaporation method in order to systematically highlight the influence of process parameters (organic solvent mixture, PVA concentration and polymeric solution volume) on NPs sizes.
Conclusion: PLGA was successfully functionalized with two different peptides, FQPV and GE11, following the a versatile and simple carbodiimmide chemistry without further modifying polymer and/or peptide structure. Both nanoprecipitation and solvent extraction/evaporation NPs preparation methods were properly optimized in order to obtain peptide-PLGA based NPs and they can be alternatively selected according to solubility properties of both peptide-polymer conjugate and drug intended for encapsulation. Peptide adsorption on preformed PLGA NPs could be efficiently used to increase peptide expression on NPs surface thus improving cellular recognition in case of active targeting. Preliminary cytocompatibility evaluation of the selected peptide-PLGA based nanoparticulate materials shows a potential feasibility of the set-up synthetic procedures and NPs preparation methods for pharmaceutical purposes.

Effect of Carbon Fiber Fabric Oxidation in Polyamide 6 Based Composites by Cristina-Elisabeta Pelin, Denisa Ficai, Ecaterina Andronescu, George Pelin, Adriana Stefan, Roxana Tru sc a (357-364).
Background: One of the major issues of carbon fiber reinforced polymeric composites is the weak interface between the phases, that supports crack propagation and leads to premature mechanical failure. The paper presents a study involving carbon fiber compatibilization with the polymeric matrix via oxidative treatment and the effect that the modified carbon fiber fabric has on the mechanical performance of its polyamide 6 composites.
Methods: Thermoplastic polyamide 6 matrix/fabric based composites are obtained using carbon fiber fabric that is oxidized using K2Cr2O7/H2SO4 mixture in different reaction conditions. The oxidized carbon fiber surface is analysed using FTIR spectroscopy and the composite materials are mechanically tested in terms of tensile and flexural properties, the fracture cross section is analyzed by SEM and optical microscopy to evaluate the interface and the fracture mode.
Results: FTIR spectroscopy showed that higher temperature oxidation generates more functional groups on the carbon fiber surface that are able to interact with the polymer, enhancing the interface strength. Tensile and flexural tests showed significant improvement of strength and stiffness when using surface oxidized carbon fabric, results owned to the excellent bonding between the matrix and the fibers that compose the fabric, illustrated by SEM and optical microscopy analysis.
Conclusion: The obtained results prove that carbon fiber oxidation in certain condition is efficient for achieving stronger fiber/themoplastic matrix interface, by creating hydrogen bonding sites that prevent delamination and are able to improve the mechanical performance of the composites.

Background: Titanium dioxide (TiO2) powders with visible-light photoactivities are in great demand for application in solar cells and solar photocatalysis. Although pure TiO2 is active only under ultraviolet light, its band gap can be narrowed down to the visible-light by impurity doping and creation of surface defects. Visible-light active anatse TiO2 powder attracts a great research interest because of its higher efficiency observed in water splitting, hydrogen generation and solar photocatalysis.
Methods: Nitrogen doped TiO2-C composite nanoparticles were synthesized in large scale by a simple and efficient chemical reaction using oleic acid and titanium tetra-isopropoxide as the precursors. The composition of the powder was analyzed by X-ray photoelectron spectroscopy, the structure was studied with X-ray diffraction and transmission electron microscopy and the optical property was studied by uv-vis absorption. The visible photocatalytic activity of black TiO2 powder was investigated by studying the photobleaching of methylene blue under solar irradiation. The effect of surface concentration of the carbon and nitrogen on the visible photocatalytic efficiency of the black-TiO2 was studied and reported. White TiO2 powder without surface carbon was also synthesized and all the properties of the above was compare with that of the black TiO2 powder.
Results: Black TiO2 was purely anatase whereas white TiO2 had mixed phase character with 68% anatase and 32% rutile. Compared to white TiO2, black TiO2 could absorb more visible light. Unlike white TiO2, Black TiO2 is an efficient solar photocatalyst responsible for the photodegradation of 52 µM aqueous solution of MB with a first order rate constant, k = 0.02 min-1. The photocatalytic activity of black-TiO2 strongly depended on the surface carbon concentration. The photocatalytic activity of black-TiO2 increases with increased carbon content. When the surface concentration exceeded 28%, the catalytic activity decreased presumably due to slower rate of charge transfer onto the TiO2 nanoparticle surface. No such systematic change in the photocatalytic activity of black-TiO2 was observed with change in its N content.
Conclusion: The visible-light active TiO2-C nanocomposite powder is very important for environmental applications. Environmental remedies such as water purification, prevention of indoor air pollution and outdoor self-cleaning process can be taken up with a low cost but highly efficient black TiO2-C photocatalyst.

Cell Bystander Effect Induced by Radiofrequency Electromagnetic Fields and Magnetic Nanoparticles by M. P. Calatayud, L. Asin, A. Tres, G. F. Goya, M. R. Ibarra (372-377).
Induced effects by direct exposure to ionizing radiation (IR) are a central issue in many fields like radiation protection, clinic diagnosis and oncological therapies. Direct irradiation at certain doses induce cell death, but similar effects can also occur in cells no directly exposed to IR, a mechanism known as bystander effect. Non-IR radiofrequency waves can induce the death of cells loaded with MNPs in a focused oncological therapy known as magnetic hyperthermia. Indirect mechanisms are also able to induce the death of unloaded MNPs cells. Using in vitro cell models, we found that co-localization of the MNPs at the lysosomes and the non-increase of the temperature induces bystander effect under non-IR. Our results provide a landscape in which bystander effects are a more general mechanism, up to now only observed and clinically used in the field of radiotherapy.

Acyclovir Entrapped N-Trimethyl Chitosan Nanoparticles for Oral Bioavailability Enhancement by Ushasree Medikonduri, Zenab Attari, Krishnamurthy Bhat, Shaila Lewis (378-385).
Objective: The aim of the study was to evaluate a nanoparticulate system composed of Ntrimethyl chitosan (TMC) for improving the oral bioavailability of Acyclovir (ACV).
Methods: TMC was prepared by methylation of chitosan and characterized by H-NMR spectroscopy. The ionic gelation method was used to prepare ACV loaded TMC nanoparticles. Non-everted sac technique was used to assess ex vivo permeation in rats. A pharmacokinetic study of the optimized formulation was carried out in male Wistar rats in comparison with ACV alone.
Results: Ex vivo studies exhibited a significant rise in the permeation of ACV from the rat intestinal membrane when formulated as nanoparticles. The results showed an increase in plasma concentration of ACV from the nanoformulation and significant difference (p < 0.05) in pharmacokinetic parameters as compared to pure drug, ACV.
Conclusion: The results suggest that higher oral delivery of ACV can be achieved by combining the benefits of both TMC and nanoparticles.

Surface Functionalized Luminescent Nanocrystals Electrostatically Assembled onto a Patterned Substrate by Michela Corricelli, Roberto Comparelli, Nicoletta Depalo, Elisabetta Fanizza, Veera B. Sadhu, Jurriaan Huskens, Angela Agostiano, Marinella Striccoli, Maria L. Curri (386-395).
Background: In the last decades, the enormous interest in 2/3D nanocrystal (NC) architectures boosted the development of many and diverse techniques which allowed to precisely positioning the nanoparticles on substrates. The tremendous importance of such NC organizations is due to the novel collective properties arising from inter-particle interactions that emerge in these articial materials, with promising application in opto-electronics, photonics and biomedicines.
Methods: Properly synthesized luminescent colloidal CdSe@ZnS NCs, coated by a silica shell, have been functionalized introducing specific chargeable moieties at their surface. At the same time, a patterned substrate has been fabricated by NanoImprint Lithography (NIL) on a polymer film deposited on a silicon substrate, resulting in polymeric structures alternating to bare silicon regions. Such “polymer-free” area have been further functionalized with charged bifunctional molecules to form a self-assembled monolayer (SAM), able to attract, by electrostatic interactions, the silanized NCs.
Results: The directed self-assembly of the luminescent silica coated CdSe@ZnS NCs, onto a patterned substrate, has been shown. The functionalized NCs are organized onto appropriately functionalized and patterned substrates, by means of electrostatic interactions. The driven assembly of the NCs allows to obtain the formation of geometrically defined luminescent patterns on silicon substrates.
Conclusion: The presented procedure ingeniously combine a top-down fabrication technique, NIL, with a bottom-up electrostatic self-assembly approach, achieving a versatile tool for fabricating original functional superstructures. Importantly, the surface functionalization, both of NCs and template substrate, has been shown to play a crucial role in the fabrication of the NC patterns, thus providing promptly integrable and versatile functional platforms, potentially useful for photonic and biosensing applications.

Background: Quantum dots are novel nanomaterials with high potential in the biomedical field.
Methods: This manuscript reports the direct aqueous synthesis of Cu-doped Zn(Se,S) quantum dots (QDs) via a microwave irradiation-assisted technique.
Results: X-ray diffractometry measurements suggested that synthesized nanostructures exhibited a Zn(Se,S) solid solution-like structure with an average crystallite size estimated at 3.6 ± 0.3 nm, which was also corroborated by High-Resolution Transmission Electron Microscopy. Fluorescence measurements of the QDs revealed a green emission peak, centered on 519 nm, that would confirm the actual incorporation of copper species into the Zn(Se,S) host. The toxicity of light-activated QDs was evaluated in cell lines of pancreatic cancer, PANC-1. The viability assay for the PANC-1 control group after 15 minutes of UV exposure was 83% ± 8%. This value went down to 40% ± 7% and 25% ± 2% after contacting the cells with Cu-doped Zn-based QDs, (50 g/mL), for UV irradiation times of 15 minutes and 60 minutes, respectively.
Conclusion: The confirmed capacity of the QDs to generate cytotoxic singlet oxygen species could explain their observed light-enhanced toxicity towards PANC-1. Accordingly, as-synthesized Cu-doped Zn-based QDs can be potentially considered as direct photosensitizers for bio-medical applications.