​​​نظم قسم الفيزياء الندوة العلمية العشرون لهذا العام بعنوان:
 

تطوير مركبات الكاليكس المعتمدة على الحساسات الفيزيائية (أنظمة الميكروكانتلفر)  للأستخدام في الاكتشاف السريع والحساس والمتزامن للمعادن في المحاليل المائية

Development of Calix[4]arene-Functionalized Microcantilever Array Sensing System for the Rapid, Sensitive and Simultaneous Detection of Metal Ions in Aqueous Solutions

(تجدون أدنا ملخص الندوة)

قدم الندوة مشكوراً الدكتور عبدالله بن ناصر العضيب (تجدون أدناه نبذة عن المقدم). كان ذلك يوم الثلاثاء 03 شعبان 1437هـ الموافق 10 مايو 2016م، وذلك من الساعة 11 صباحاً ولمدة نصف ساعة. هذا وقد تلى الندوة مداخلات وأسئلة من الحضور.

 تأتي هذه الندوة ضمن سلسلة ندوات دورية تنظمها اللجنة العلمية بقسم الفيزياء ويقدمها أعضاء هيئة التدريس بالقسم وباحثون من جهات بحثية أخرى، تهدف هذه الندوات إلى تحفيز مناخ البحث العلمي بالقسم وإطلاع منسوبيه على آخر ما توصلت إليه العلوم الفيزيائية في شتى المجالات.

جدير بالذكر أن الحضور لهذه الندوات متاح لجميع منسوبي الجامعة من أعضاء هيئة تدريس وموظفين وطلاب.

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Abstract:

This work was conducted with the aim of: 1) investigating the binding capabilities of calix[4]arene-functionalized microcantilevers towards specific metal ions and 2) developing a new16-microcantilever array sensing system for the rapid, and simultaneous detection of metal ions in fresh water.

Part I of this work reports on the use of three new bimodal calix[4]arenes (methoxy, ethoxy and crown) as potential host/guest sensing layers for detecting selected ions in dilute aqueous solutions using single microcantilever experimental system. In this work it was shown that modifying the upper rim of the calix[4]arenes with a thioacetate end group allow calix[4]arenes to self-assemble on Au(111) forming complete highly ordered monolayers. It was also found that incubating the microcantilevers coated with 5 nm of Inconel and 40 nm of Au for 1 h in a 1.0 M solution of calix[4]arene produced the highest sensitivity. Methoxy-functionalized microcantilevers showed a definite preference for Ca2+ ions over other cationic guests and were able to detect trace concentration as low as 10-12 M in aqueous solutions. Microcantilevers modified with ethoxy calix[4]arene displayed their highest sensitivity towards Sr2+ and to a lesser extent Ca2+ ions. Crown calix[4]arene-modified microcantilevers were however found to bind selectively towards Cs+ ions. In addition, the counter anion was also found to contribute to the deflection.  For example methoxy calix[4]arene-modified microcantilever was found to be more sensitive to CaCl2 over other water-soluble calcium salts such as Ca(NO3)2 , CaBr2 and CaI2. These findings suggest that the response of calix[4]arene-modified microcantilevers should be attributed to the target ionic species as a whole instead of only considering the specific cation and/or anion.

Part II presents the development of a 16-microcantilever sensor setup. The implementation of this system involved the creation of data analysis software that incorporates data from the motorized actuator and a two-axis photosensitive detector to obtain the deflection signal originating from each individual microcantilever in the array. The system was shown to be capable of simultaneous measurements of multiple microcantilevers with different coatings. A functionalization unit was also developed that allows four microcantilevers in the array to be coated with an individual sensing layer one at the time. Because of the variability of the spring constants of different cantilevers within the array, results presented were quoted in units of surface stress unit in order to compare values between the microcantilevers in the array.

Biography:

Abdullah  Alodhayb  received  his  B.Sc.  degree in  physics  in  2007.  He  then  received  his  Master’s  degree  in  physics  from Memorial  University  of  Newfoundland  in  Canada  in  2011.  His research during the M.Sc.  program  was  dedicated  to  detecting  the  human  immunodeficiency  virus  (HIV) using  microcantilever  sensors.  He has recently completed a  Ph.D.  degree in  condensed  matter physics,  in  the  sensors  group  in  the  Department  of  Physics  and  Physical  Oceanography  at  Memorial  University.  His research interests  include  the  use  of  chemical sensors  in  studying  host–guest  compounds  and  the  use  of  STM  in  investigating  the formation  of  SAMs  on  Au-coated  microcantilever.