Higher stability and better photoluminescence quantum yield of cesium lead iodide perovskites nanoparticles in the presence of CTAB ligand

Inorganic halide perovskites, such as CsPbI3, have unique optoelectronic properties which made them promising candidates for several applications. Unfortunately, these perovskites undergo rapid chemical decomposition and transformation into yellow δ-phase. Thus, the synthesis of stable cesium lead iodide perovskites remains an actual challenging field and it is imperative to develop a stabilized black phase for photovoltaic applications. For this purpose, a surfactant ligand was used to control the synthesis of inorganic perovskite CsPbI3 nanoparticles. Herein we demonstrate a new avenue for lead halide perovskites with the addition of either hexadecyltrimethylammonium bromide (CTAB) or silica nanoparticles to maintain in the first place; the stability of the α-CsPbI3 phase, and later on to boost their photoluminescence quantum yield (PLQY). The prepared perovskites were characterized using UV-visible absorption spectroscopy, fluorescence spectroscopy, scanning electron microscopy, thermogravimetric analysis and X-Ray diffraction technique. Results show higher stability of α-CsPbI3 phase and improvement in PLQY % to reach 99% enhancement in presence of CTAB. Moreover, the photoluminescence intensity of CsPbI3 nanoparticles was higher and was maintained for a longer duration in the presence of CTAB.

Curcumin-PLGA based nanocapsule for the fluorescence spectroscopic detection of dopamine

The main purpose of this paper is to design curcumin loaded PLGA nanocapsules for the selective detection of dopamine using fluorescence spectroscopy. In the present work curcumin loaded PLGA nanocapsules were synthesized using a solid-in-oil-in water (s/o/w) emulsion technique. The prepared nanocapsules were coated with a poly(diallyldimethylammonium)chloride (PDDA) polymer to increase the entrapment of curcumin into the core of PLGA polymer. PLGA-Cur-PDDA nanocapsules were characterized using different microscopic and spectroscopic techniques. Unlike free curcumin, the formed CUR-PLGA-PDDA NCs were established as nanoprobes for the selective detection of dopamine molecules. The selectivity and specificity of nanocapsules toward dopamine was achieved by measuring the fluorescence emission spectra of the NCs in the presence of other interference molecules such as tryptophan, melamine, adenine, etc. It was noticed that increasing the concentration of the different molecules had no significant change in the fluorescence signal of the nanocapsules. These results confirm the strong quenching between dopamine and curcumin in the nanocapsules. Hence, this fluorescence emission technique was found to be selective, easy and fast with low cost for the determination of dopamine in a concentration range up to 5 mM with a detection limit equal to 22 nM.

Cesium Lead Bromide Perovskites: Synthesis, Stability, and Photoluminescence Quantum Yield Enhancement by Hexadecyltrimethylammonium Bromide Doping

Perovskite nanoparticles having a crystalline structure have attracted scientists' attention due to their great potential in optoelectronic and scintillation applications. The photoluminescence quantum yield (PLQY) is one of the main critical photophysical properties of the perovskite nanoparticles. Unfortunately, the main limitation of cesium lead halide perovskites is their instability in an ambient atmosphere, where they undergo a rapid chemical decomposition within time. For this purpose, hexadecyltrimethylammonium bromide (CTAB) was used as a surfactant dopant to test in the first place its effect on the stability of CsPbBr₃ perovskites and on the PLQY values of the prepared perovskites. The addition of CTAB has proven its efficiency in the formed CsPbBr₃ nanoparticles by increasing their thermal stability and by enhancing their PLQY up to 75%. These results were obtained after the successful preparation of CsPbBr₃ perovskite nanoparticles by optimizing three different reaction parameters, starting from the time of the reaction, moving to the concentration of lead bromide, and ending with the concentration of cesium oleate. Therefore, it was found that the most stable CsPbBr₃ perovskites were formed when mixing 0.15 g of lead bromide heated for 40 min with a volume of 1.2 mL of cesium oleate.

A Novel Study on the Self-Assembly Behavior of Poly(lactic-co-glycolic acid) Polymer Probed by Curcumin Fluorescence

Understanding the self-assembly behavior of block copolymers is of great importance due to their usefulness in a wide range of applications. In this work, the physical properties of poly(lactic-co-glycolic acid) (PLGA polymer) are studied for the first time in solution using the fluorescence technique and curcumin as a molecular probe. First, curcumin at a concentration of 2 μM was added to different concentrations of PLGA, and the fluorescence of curcumin was tracked. It was found that the critical micellar concentration (CMC) was equal to 0.31 g/L and the critical micellar temperature (CMT) was obtained to be 25 °C. Furthermore, an insight on the effect of NaCl salt on the CMC value of PLGA is assessed through curcumin probing. A decrease in the CMC has been observed with the increase in the concentration of NaCl, which could be due to the salting out effect. Moreover, in order to understand the aggregation behavior of PLGA in different solutions, CMC experiments were investigated using chloroform as a solvent. Results showed that the solvent does not affect the CMC value of the polymer; however, it only affects the shape of the obtained micelle forming a reversed micelle. Finally, fluorescence quenching of curcumin with hydrophobic cetyl-pyridinium bromide (CPB) and hydrophilic KI quenchers was established, where it was proved that curcumin is located near the hydrophobic pocket of the Stern layer of the PLGA micelle.

Curcumin-embedded DBPC liposomes coated with chitosan layer as a fluorescence nanosensor for the selective detection of ribonucleic acid

One of the limitations of fluorescence probe molecules during biomedical estimation is their lack of ability to selectively determine the targeted species. To overcome this there have been various approaches that involve attaching a functional group or aptamers to the fluorescence probe. However, encapsulating probe molecules in a matrix using nanotechnology can be a viable and easier method. Curcumin (Cur) as a fluorescence marker cannot distinguish DNA and RNA. This research reports a novel selective approach involving the use of nanocapsules composed of liposomal curcumin coated with chitosan for the selective detection of RNA molecules using a fluorescence method. The increase in RNA concentration enhanced the electrostatic interaction between the negatively charge surface of RNA and the positively charged nanocapsule, which was further verified by zeta potential measurement. This method had a low limit of detection (36 ng/ml) and higher linear dynamic ranges compared with other studies found in the literature. Moreover, the method was not affected by DNA and was selective for the detection of RNA molecules for which the site of interaction was confined only to uracil. The selectivity for RNA molecules towards other analogues species was also examined and recovery range found was between 99 and 100.33%.

Liposome-based nanocapsules for the controlled release of dietary curcumin: PDDA and silica nanoparticle-coated DMPC liposomes enhance the fluorescence efficiency and anticancer activity of curcumin

Nanosystems with various compositions and biological properties are being extensively investigated for drug and gene delivery applications. Many nanotechnology methods use novel nanocarriers, such as liposomes, in therapeutically targeted drug delivery systems. However, liposome matrices suffer from several limitations, including drug leakage and instability. Therefore, the surface modification of liposomes by coating them or adding polymers has advanced their application in drug delivery. Hence, the prevention of drug release from the liposome bilayers was the main focus of this work. For this purpose, liposomes were synthesized according to a thin film hydration method by applying various surface modifications. Three different nanocapsules, N1, N2, and N3, were prepared using 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), poly(diallyldimethylammonium)chloride (PDAA) polymer, and silica nanoparticles. PDDA and silica nanoparticles were coated on the surface of liposomes using a layer-by-layer assembly method, completely encapsulating curcumin into the core of the liposome. Fluorescence spectroscopy, TGA, DLS, XRD, SEM, and zeta potential methods were used to characterize the prepared nanocapsules. Interestingly, the fluorescence of curcumin showed a blue shift and the fluorescence efficiency was extraordinarily enhanced ∼25-, ∼54-, and ∼62-fold in the N1, N2, and N3 nanocapsules, respectively. Similarly, encapsulation efficiency, drug loading, and the anticancer activity of dietary curcumin were investigated for the different types of DMPC nanocapsules. The drug efficiencies of the liposomes were established according to the release of curcumin from the liposomes. The results showed that the release of curcumin from the nanocapsules decreased as the number of layers at the surface of the liposomes increased. The release of curcumin follows the Higuchi model; thus, a slow rate of diffusion is observed when a number of layers is added. The better encapsulation and higher anti-cancer activity of curcumin were also observed when more layers were added, which is due to electrostatic interactions inhibiting curcumin from being released.

Nanosystems with various compositions and biological properties are being extensively investigated for drug and gene delivery applications.

Efficient removal of Congo red using curcumin conjugated zinc oxide nanoparticles as new adsorbent complex

Congo red is one of the common organic dyes that is found in water as waste of the industrial work. The use of congo red has long been of great concern, primarily because of its carcinogenic properties. Congo red can be isolated and removed from water by adsorption using nanoparticles. The use of zinc curcumin oxide, also known as curcumin conjugated zinc oxide, nanoparticles was elaborated for the first time in this work for this purpose. The optimization of the synthesis reaction of zinc curcumin oxide nanoparticles was established by modifying the flow rate of KOH, pH of the medium, different temperature, and in the presence or absence of chitosan polymer. These nanoparticles were characterized through SEM, UV-Visible absorption Spectroscopy, fluorescence spectroscopy, TGA, and XRD. It is found that during synthesis, addition of KOH dropwise in alkaline media improved the stability of the formed nanoparticles. Similarly, addition of chitosan has further increased their stability with only 10% mass loss. The importance of the formed nanoparticles was investigated by analyzing their efficiency in the adsorption of congo red where Zn(Cur)O had an adsorption capacity equal to 89.85 mg/g, which is one of the highest reported in literature, following the pseudo second order model. Nevertheless, negative surface charge of congo red and positive surface charge of Zn(Cur)O may also get supported by π-π interaction between curcumin and congo red that encourages adsorption in zinc curcumin oxide which is obstructed in the presence of chitosan.

Interaction of curcumin with diarachidonyl phosphatidyl choline (DAPC) liposomes: Chitosan protects DAPC liposomes without changing phase transition temperature but impacting membrane permeability

The developing public interest in traditional medicine, especially plants-based drug, has prompted extensive research on the potential of naturally existing compounds. Among these compounds, curcumin is currently one of the most studied substances. In this study, we elaborate the physical properties of diarachidonyl phosphatidyl choline (DAPC) liposome using fluorescence method, where curcumin at low concentration was used as a probe molecule. In the first place, the phase transition temperature of DAPC was determined by following the fluorescence intensity of curcumin as a function of temperature, along with evaluating the effect of concentration of curcumin in the presence or absence of chitosan oligosaccharide lactate as an additional protective layer. On the other hand, quenching reactions using CPB and KI as quenchers reflected the ease of entry of different concentrations of these quenchers to the curcumin located in the hydrophobic core of the liposome which give new insight about the lipophilicity and permeability of the DAPC membrane. Finally, the partition coefficient analysis was investigated. It was concluded that curcumin has a higher partition coefficient at a temperature above the phase transition temperature of DAPC liposomes where the liposome is in the fluid liquid crystalline phase. Modulation of liposomes properties in the presence of chitosan oligosaccharide lactate layer was for the first time investigated. Chitosan oligosaccharide lactate acts as protecting layer without changing the phase transition temperature, but it affects the membrane permeability depending on solid gel and liquid crystalline phase.

Introducing Principal Coordinate Analysis (PCoA) Assisted EEMF Spectroscopic Based Novel Analytical Approach for the Discrimination of Commercial Gasoline Fuels

In the present work, a novel analytical procedure by integrating principal coordinate analysis (PcoA) with excitation-emission matrix fluorescence (EEMF) spectroscopy was introduced for discriminating the commercial gasoline fuels. The PcoA technique involved analysis of the distance matrices containing the dissimilarity information and it can serve as an efficient tool for capturing the major as well as subtle compositional differences among the analyzed commercial gasoline samples. The utility of the proposed PcoA assisted EEMF analytical procedure was successfully tested by discriminating gasoline fuel samples belonging to five different industrial brands. The obtained results clearly showed that combination of PcoA and EEMF could provide a simple, sensitive and economical analytical procedure to carry out the rapid analyses of the gasoline samples belonging to different brands.

Curcumin encapsulated colloidal amphiphilic block co-polymeric nanocapsules: colloidal nanocapsules enhance photodynamic and anticancer activities of curcumin

Curcumin-based novel colloidal nanocapsules were prepared from amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F108). These colloidal nanocapsules appeared as spherical particles with size ranging between 270 and 310 nm. Curcumin fluorescence spectra exhibited an aggregation-induced 23 nm red-shift of the emission maximum in addition to the enhancement of the fluorescence quantum yield in these nanocapsules. The cytotoxicity of curcumin and colloidal nanocapsules was assessed using human derived immortalized cell lines (A549 and A375 cells) in the presence and absence of light irradiation. The nanocapsules exhibited a >30-fold decrease in IC₅₀, suggesting enhanced anticancer activity associated with curcumin encapsulation. Higher toxicity was also reported in the presence of light irradiation (as shown by the IC₅₀ data), indicating their potential for future application in photodynamic therapy. Finally, A375 cells treated with curcumin and the nanocapsules showed a significant increase in single- and/or double-strand DNA breaks upon exposure to light, indicating promising biological effects.

Fluorescence Sensing of Nucleic Acid by Curcumin Encapsulated Poly(Ethylene Oxide)-Block-Poly(Propylene Oxide)-Block-Poly(Ethylene Oxide) Based Nanocapsules

In a novel approach, curcumin has been encapsulated inside Poly(Ethylene Oxide)-Block-Poly(Propylene Oxide)-Block-Poly(Ethylene Oxide) (F108) nanocapsules. FTIR spectra have indicated a type of hydrogen bonding and dipole interaction between curcumin and F108. Fluorescence and UV-visible absorption profiles of curcumin in nanocapsules have indicated location of curcumin in more hydrophobic microenvironment. The relative fluorescence yield has increased by 6 times in the nanocapsules, which renders them as more sensitive probes to be used later on in sensing study. Therefore, based on the functionality of curcumin as a fluorescent transducer, encapsulated curcumin is used in biomedical application as DNA and RNA sensing. Detection limits are detected as 50 μM and 60 μM for DNA and RNA respectively. Linear dynamic concentration range obtained in this proposed method is much higher than reported in literature. The interaction between the nanocapsules and targeted DNA/RNA molecules is further approved by zeta potential studies. Furthermore, the real interaction of DNA with the encapsulated curcumin is confirmed by the interaction of the adenine and cytosine nucleotides. This has been verified through zeta potential measurements. Moreover, our prepared nanocapsules has presented a high percentage recovery of DNA and RNA (96-101%). Finally, stability results have illustrated a high photostability of encapsulated curcumin, indicating that proposed nanocapsules can be considered as a stable sensor during measurement time.

Random initialisation of the excitation-emission matrix fluorescence spectral variables in constraint fashion for subsequent multivariate curve resolution alternating least square analysis on a peculiarly designed calibration set: Simultaneous sensing of nine polycyclic aromatic hydrocarbons in water samples

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and mutagenic in nature therefore their sensing in water sample is an important analytical task. In the present work, a novel approach that is based on the random initialisation of the excitation-emission matrix fluorescence (EEMF) spectral variables in constraint fashion for subsequent multivariate curve resolution alternating least Square (MCR-ALS) analysis is introduced for simultaneously sensing the complex dilute aqueous mixture of PAHs. The usefulness of the proposed analytical approach is successfully demonstrated by applying it intentionally on a calibration set that is peculiar in many senses. The peculiarity mainly arises because the designed (i) the calibration set consist of nine PAHS having significant spectral overlap, (ii) the concentration of each PAH in different samples are kept constant and (iii) any two samples differ only in the presence and absence of the PAHs. The proposed approach is found to make precise and accurate estimation of each of the nine PAHs without involving any pre-separation. In summary, the proposed approach provides a simple and cost-effective procedure for simultaneous sensing of several PAHs in water samples. The proposed approach could be very useful in developing countries.

The role of OH- in the formation of highly selective gold nanowires at extreme pH: multi-fold enhancement in the rate of the catalytic reduction reaction by gold nanowires

There is a quest to understand the mechanism governing the morphology and geometry control of the particle growth of nanomaterials for their optical and catalytic applications. In the available literature, the role of OH^- in dictating the size and shape of Au nanowires is unknown. As one of the first examples, herein, we explore how excess OH^- ions in CTAB micelles play a significant role during the highly selective formation of gold nanowires having controlled diameters of ∼20-25 nm and length >1 μm, by reducing Au³⁺ to Au⁰ in a one pot, simple synthesis procedure in the presence of Ag⁺ ions. At pH 4-11, the same procedure does not harvest Au NWs, but Au NPs of diameter 50-70 nm, indicating that excess OH^- is needed for nanowire formation. XRD, TGA, DSC, EDX, FT-IR and fluorescence spectroscopic analysis confirm that both CTAB and curcumin act as capping and stabilizing agents for Au NWs as well as Au NPs - there is no remarkable difference in the curcumin/CTAB content between Au NWs and NPs prepared in different pH environments. However, changing the CTAB micellar media to DPPC liposome media inhibits the formation of nanowires at pH ∼13; the growth of the Au NPs diminishes in DPPC liposomes, offering smaller NPs of diameter ∼25 to 30 nm, suggesting that the role of CTAB is necessary in nanowire formation. The rate of NW formation has been found to be 0.13 h^-1 and the growth mechanism advocates elongation in the [110] facet of Au [110] as opposed to the [100] or [111] facets. Curcumin capped Au nanowires serve as excellent nano-catalysts for the reduction of nitro-compounds and the rate of reduction of 4-nitrophenol, a model compound, by curcumin capped Au NWs is found to be ∼10 fold higher, compared to Au NPs, which signifies that catalytic activities can be dictated by the size and shape of Au NPs.

Tuning the surface of Au nanoparticles using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol): enzyme free and label free sugar sensing in serum samples using resonance Rayleigh scattering spectroscopy

Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F-108) functionalized gold nanoparticles (Au NPs) have been successfully synthesized for glucose estimation.

Amplification of resonance Rayleigh scattering of gold nanoparticles by tweaking into nanowires: Bio-sensing of α-tocopherol by enhanced resonance Rayleigh scattering of curcumin capped gold nanowires through non-covalent interaction

Tuning optical properties by controlling size and shape of the metallic nanoparticles has been of great interest to design novel bio-sensing techniques. Here, as a first example we illustrate that resonance Rayleigh scattering (RRS) signal of Au nanoparticles (NPs) can be amplified >10-fold by growing into Au nanowires (NWs). These thin and long NWs of ~20-25nm diameter and >1µm length can be achieved by suitably manipulating the temperature during green synthesis using curcumin. Interestingly, mixture of Au NWs and NPs or shorter NWs gives a moderate increase in RRS signal suggesting formation of longer NWs is crucial for optimal enhancement of RRS signal. Curcumin along with CTAB act as capping and stabilizing agent for Au NWs/NPs in different temperatures, which is confirmed by XRD, TGA, DSC, EDX and FT-IR data. This amplified RRS signal of Au NWs has been employed to design a new optical biosensor for α-tocopherol (α-TOH), which is among the most biologically active form of vitamin E. Association of α-TOH with Au NWs further enhances the RRS signal of Au NWs, ~10 fold through non-covalent interaction. No interference from other antioxidant substances like ascorbic acid and 6-O-Palmitoyl-L-ascorbic acid is observed. The sensing method is simple, fast and offers remarkable linear dynamic ranges, 12.8-1004µmolL^-1, which is larger than reported values. The detection limit for α-TOH estimation has been found to be 50nmolL^-1. The biosensor is found to be stable both in the absence and presence of α-TOH and provides an excellent recovery for synthetic samples.