Conference Programme

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Overview
Session
N-06: Symp N
Time:
Wednesday, 21/Jun/2017:
10:30am - 12:00pm

Session Chair: John Wang, National University of Singapore
Session Chair: Guozhu Chen, University of Jinan
Location: Rm 304

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Presentations
10:30am - 11:00am
Invited

Near-Infrared Excited Nanoplatforms: Applications in Nanomedicine

Fiorenzo VETRONE

Institut National de la Recherche Scientifique (INRS) University, Canada

The ability to stimulate luminescent inorganic nanoparticles with near-infrared (NIR) light has made possible their use in a plethora of biological and medical applications. In fact, the biggest impact of such materials would be in the field of disease diagnostics and therapeutics, now commonly referred to as theranostics. The use of NIR light for excitation mitigates some of the drawbacks associated with high-energy light (UV or blue) excitation, for example, little to no background autofluorescence from the specimen under investigation as well as no incurred photodamage. Moreover, one of the biggest limitations is of course, that of penetration. As such, NIR light can penetrate tissues much better than high-energy light especially when these wavelengths lie within the three so-called biological windows. Thus, significant strides have been made in the synthesis of inorganic nanomaterials whose excitation as well as emission bands lie within one of these three optically transparent biological windows. Here, we present the synthesis of various NIR excited (and emitting) inorganic core/shell (and hybrid) nanostructures and demonstrate their potential use in nanomedicine. Furthermore, we will show how such nanoparticles can be used as building blocks towards developing multifunctional nanoplatforms for simultaneous detection and therapy of disease.


11:00am - 11:30am
Invited

Upconversion Nanocrystals: The Search for High Efficiency Luminescent Bioprobes

Xiaogang LIU1,2

1National University of Singapore, Singapore; 2Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore

Lanthanide-doped nanoparticles exhibit unique luminescent properties, including a large Stokes shift, a sharp bandwidth of emission, high resistance to optical blinking, and photobleaching. Uniquely, they can also convert long-wavelength stimulation into short-wavelength emission. These attributes offer the opportunity to develop alternative luminescent labels to organic fluorophores and quantum dots. In recent years, researchers have taken advantage of spectral-conversion nanocrystals in many important biological applications, such as highly sensitive molecular detection and autofluorescence-free cell imaging. With significant progress made over the past several years, we can now design and fabricate nanoparticles that display tailorable optical properties. In particular, we can generate a wealth of color output under single-wavelength excitation by rational control of different combinations of dopants and dopant concentration. By incorporating a set of lanthanide ions at defined concentrations into different layers of a core-shell structure, we have expanded the emission spectra of the particles to cover almost the entire visible region, a feat barely accessible by conventional bulk phosphors. In this talk, I will highlight recent advances in the broad utility of upconversion nanocrystals for multimodal imaging, bio-detection, display and photonics.


11:30am - 12:00pm
Invited

Effect of Pressure on TiO2 Crystallization Kinetics using In-situ High Temperature Synchrotron Radiation Diffraction

Hani ALBETRAN1,2, Brian O'CONNOR1, It-Meng {Jim} LOW1

1Curtin University, Australia; 2Imam Abdulrahman Alfaisal University, Saudi Arabia

The phase transformation behavior of TiO2 sol–gel synthesized nanopowder heated in a sealed quartz capillary from room temperature to 800°C was studied using in-situ synchrotron radiation diffraction (SRD). Sealing of the capillary resulted in an increase in capillary gas pressure with temperature. The pressures inside the sealed capillary were calculated using Gay-Lussac’s Law, and they reached 0.36 MPa at 800°C. The as-synthesized material was entirely amorphous at room temperature, with crystalline anatase first appearing by 200°C (24 wt% absolute), then increasing rapidly in concentration to 89 wt% by 300°C and then increasing more slowly to 97 wt% by 800°C, with there being no indication of the anatase-to-rutile transformation up to 800°C. The best estimate of activation energy for the amorphous-to-anatase transformation from the SRD data was 10(2) kJ/mol, which is much lower than that observed when heating the material under atmospheric pressure in a laboratory-XRD experiment, 38(5) kJ/mol. For the experiment under atmospheric pressure, the anatase crystallization temperature was delayed by ca. 200°C, first appearing after heating the sample to 400°C, after which crystalline rutile was first observed after heating to 600°C. The estimated activation energy for the anatase-to-rutile transformation was 120(18) kJ/mol, which agrees with estimates for titania nanofibers heated under atmospheric pressure. Thus, heating the nanopowders material under pressure promoted the amorphous-to-anatase transformation, but retarded the anatase-to-rutile transformation. This behavior is believed to occur in an oxygen-rich environment and interstitial titanium is expected to form when the material is heated under pressure. This suggests that atmospheric oxygen appears to accelerate the amorphous-to-anatase transformation, whereas interstitial titanium inhibits TiO2 structure relaxation, which is required for the anatase-to-rutile transformation.


12:00pm - 12:15pm
Oral

Giant Magnetocaloric Effect in GdAlO3 and a Comparative Study with GdMnO3

Sudipta MAHANA1,2, Manju UNNIKRISHNAN3, Dinesh TOPWAL1,2

1Institute of Physics Bhubaneswar, India; 2Homi Bhabha National Institute, India; 3CSIR-Institute of Minerals and Materials Technology, India

Now-a-days scientific and engineering efforts are directed towards magnetic refrigeration technology due to its high energy efficiency and eco-friendly characteristics over conventional gas compression/expansion cooling technology. The working principle of magnetic refrigeration is based on isothermal magnetic entropy change or the adiabatic temperature change caused by change in the magnetic field. Worldwide efforts are in its peak to find materials with very high refrigeration capacity. Generally, materials are suitable candidates for magnetic refrigeration in the vicinity of the transition temperature. The feasibility for producing magnetic refrigerator for commercial use was established in 1997 with the observation of giant magneto caloric effect (18.8 J.Kg·K−1) in Gd5Si2Ge2. The compounds based on rare-earth alloys and oxides are the candidates with the most potential, especially for low temperature applications, due to the low antiferromagnetic ordering temperature in rare-earth sub-lattice. We found a giant magnetic entropy change in GdAlO3 (40.9 J.Kg·K−1) under a field change of 9 T at cryogenic temperature, while the moderate effect of 18 J.Kg·K−1 is observed for similar compound like GdMnO3. Such a large difference is due to the additional Gd-Mn interaction in GdMnO3.



 
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