Upconverting nano-engineered surfaces: maskless photolithography for security applications

The two complementary technologies of colloidal upconverting nanoemitters and maskless photolithography are exploited to fabricate nanoengineered optically active surfaces for anticounterfeiting applications based on the multiphoton absorption phenomenon in lanthanide nanocomposites with a visualization wavelength in the NIR. It is demonstrated that the unique optical, thermal, and temporal characteristics of these versatile upconverting surface distinguishes them from their counterparts. A unique behavior that is captured is the ability to actively tune their emission color by modifying the pumping power, temperature, and excitation frequency. A new low-cost negative photoresist is employed for implementation of maskless photolithography of single- and double-color labels using two efficient upconverting nanocomposites based on NaYF4:Yb3+, Er3+ and NaYF4:Yb3+, Tm3+ nanoemitters. In addition, it is shown that the detectability of the proposed anticounterfeiting approach can be carried out using just a smartphone. Each of the emission peaks of the upconversion nanoparticles is associated with a different multiphoton absorption mechanism and their thermosensitivity varies from one peak to another. Furthermore, their photoluminescent color changes by scanning the excitation beam impinging on the surfaces composed of both upconversion nanoparticles doped in the UV-curable resist. Long-term photostability of these surfaces under continuous excitation by a high power laser makes them a promising nanoemitters for the next generation of anticounterfeiting labels

Hybrid dissolved-oxygen and temperature sensing: a nanophotonic probe for real-time monitoring of chlorella algae

Dissolved-oxygen concentration and temperature are amongst the crucial parameters required for the precise monitoring of biological and biomedical systems. A novel hybrid nanocomposite probe for real-time and contactless measurement of both dissolved-oxygen concentration and temperature, based on a combination of downconverting phosphorescent molecules of platinum octaethylporphyrin and lanthanide-doped upconverting nanoparticles immobilized in a host of polystyrene, is here introduced. Chlorella algae are employed here as a model to demonstrate the hybrid nanophotonic sensor’s capability to monitor the aforementioned two parameters during the photosynthesis process, since these are among the parameters impacting their production efficiency. These algae have attracted tremendous interest due to their potential to be used for diverse applications such as biofuel production; however, feasibility studies on their economic production are still underway

DNA structure spectroscopy by synthetic pigments using LED lighting

It is clear that DNA concentration and biological detection devices have many applications in the fields of genetics and biotechnology. For this goal, some similar devices have been designed working with the laser light which the disadvantages of them are high prices and the use of significant amounts of sample volume. But this designed device which works with LED light has very cheap manufacturing cost. The amounts of DNA used in this device are very low, about a few micro-liters and measurement of small, fast and portable it is also the advantages of these devices. The Data recorded as voltage versus time and the Fourier transform the frequency domain. From the frequency curve, by using the Byrlambrt it is possible to obtain the relative concentrations of DNA, viruses and assays measuring DNA damage and many other applications. By use of this device, the concentration of DNA colored with three different pigments was measured

Synthesis and nonlinear optical characterization of nanocrystalline

Using a plasma spray torch, nanocrystalline γ-alumina powder has been synthesized in a reactor through oxidation of micron-size aluminum metal powder by in-flight thermal plasma processing. The synthesized particles were characterized by X-ray diffraction (XRD) and field emission transmission electron microscopy (FE-TEM). The particle size was in the range of ~7 to ~56 nm and spherical in shape. Furthermore the nonlinear refractive and absorptive indices of the sample under various intensities using Z-scan and moiré deflectometry techniques by a CW He-Ne laser at 632.8 nm wavelength were measured