Name:

Benjamin Schazmann

Contact details

School of Chemical Sciences

Dublin City University

Dublin 9

Ireland

Benjamin.Schazmann2@mail.dcu.ie

Telephone 00353 1 7005670

Qualifications

B.Sc. Chemistry with extended studies in Europe, 1st Class Honours, Queen's University, Belfast, 1997.

M.Sc. Chemical Oceanography, National University of Ireland, Galway, 1999.

Ph.D. Chemical Sensors, Dublin City University, 2006.

Project Summary

 

Current Project Overview.

 

My research combines analytical and synthetic chemistry disciplines.  I am involved in the design, synthesis, isolation and characterisation of new Supramolecular Receptors.  These receptors are for use in ‘Host-Guest’ chemistry whereby a particular analyte can be selectively and reversibly detected in a sample.  My research covers a broad area from conceptual structure design to applied working sensor devices, thereby drawing on scientific and engineering skills.

 

The goal of this research is to develop useful ‘active’ compounds which can be incorporated into future sensors.  The focus is on electrochemical and optical sensors in particular.

 

Project Summary.

 

Since Autumn 2002, I have been conducting research for a PhD with the Adaptive Sensors Group (ASG) at Dublin City University.  I am currently writing up my PhD thesis and publishing the data obtained to date. 

Every chemical sensor must contain suitable reactive sites at the molecular level which through the platform of a physical device signal the presence or absence of a target analyte e.g. cations, anions or neutral species.

My current research is to develop  sensor compound followed by the incorporation of synthesised products into actual devices to tests for useful properties.  This provides an interesting overlap of synthetic and analytical chemistry as well as engineering challenges.  The synthetic work is based on molecular platforms called calixarenes (Figure 1).

 

 

Figure 1.  The general structure of calix[4]arenes.

 

Calixarenes, when adorned with functional groups at the upper or lower rim, provide rigid preorganised cavities, which can be fine tuned to incorporate a guest species, hopefully with a good degree of selectivity (only target analyte is ‘sensed’ amongst possibly similar competing guests). 

To illustrate the ‘birth’ phase of a sensor, some of the milestones of one of my sensor compounds are outlined below.

 

Synthesis and Modelling

 

Computer generated energy minimised molecular models may predict in advance or explain following synthesis, the structure and complexation behaviour of a Host molecule.  This addresses issues of geometric and size compatibility between a Host’s cavity and a particular guest.  The models also provide a powerful visualisation of the Guest binding event.  Figure 2 shows the synthesis of  tetranitrile calix[4]arene 1 and a molecular model of 1 incorporating an ammonium cation in the lower rim cavity.  This illustrates the attraction between a positively charged (red) cation and the negative (blue) electron localisation of the nitrile functional groups, leading to a Host-Guest interaction.  Atoms are scaled by size according to Huckel partial charges. 

 

Figure 2.  The synthesis of calix[4]arene Host 1 with lower rim guest cavity and a molecular model of 1 coordinating an ammonium cation Guest.

 

My research covers both inorganic cation and anion sensing.

 

Isolation and Purification

The isolation of a pure target compounds is normally carried out using silica gel in glass chromatography columns by the organic chemist.  Due to the complex mixture arising from the synthesis of 1, I developed an alternative HPLC instrumental method for the isolation of pure calixarenes.  By using a semi-preparative HPLC column, better resolving power was achieved yielding higher product yields of purer compound.  This method can be applied to any synthetic regime in theory.  Crucially, it was carried out using analytical scale instrumentation (available in any chemistry department) and a scaled up analytical method to yield mg quantities of target compound (Figure 3).  These quantities proved sufficient for characterisation and sensor testing. 

 

Figure 3.  HPLC spectra of the  crude mixture of 1 (left) and the purified compound (right).  Standard HPLC instrumentation was used with a scaled up analytical HPLC method to efficiently yield mg quantities of product in a short space of time.

 

The identity of the pure product was further varified by MS, NMR, IR and elemental analysis.

 

Potentiometric characterisation:  towards sensor

development.

With sufficient quantities of Host 1 isolated, the sensing ability thereof was tested using Ion Selective Electrodes (ISEs).  The Host was incorporated into a PVC membrane which was attached to a working electrode barrel.  Together with a reference electrode this represented a working electrochemical cell.  This process involved some engineering and electronic considerations (Figure 4).

 

 

Figure 4.  A typical potentiometric ISE setup comprising a working electrode, a reference electrode and an aqueous test solution.

By adding controlled quantities of a range of possible analytes to an aqueous solution (cations in the case of 1), potential changes were recorded using a PC/Labview interface.  The relative magnitudes of the potential change for a given analyte are related to selectivity values.  Figure 5 shows a typical ISE titration response whereby potential is plotted against activity or concentration of analyte.  A response slope of about +59mVdecade^-1 for monovalent cations indicates a well functioning electrode.

 

 

 Figure 5.  The rise in potential of an ISE is monitored upon adding increasing amounts of sodium ions to an aqueous solutions.

 

The use of electrochemical ISEs represents a practical real life means of screening a compound for ‘sensor activity’.   They can be optimised (for sensitivity, selectivity, lifetime, limit of detection etc.), miniaturised and commercialised with relative ease. 

 

Optical sensing

In parallel to my electrochemical testing, I am working on the development of optical sensors.  This may employ a supramolecular platform like a calixarene also.  In addition to adding sensing functional groups, the binding or analyte coordinating event can be signalled or transduced optically by adding an appropriate chromophore in the vicinity of the Host’s guest cavity.  When the free Host associates with a Guest, an electronic or conformational change can trigger a change in the optical properties of the Host and so the Guest analyte is sensed optically.

I am currently publishing work based on a calixarene pyrene structure.  This is envisaged as the basis for a ratiometric fluorescent sensor.  When two pyrene moieties stack in an intramolecular fashion and an excitation wavelength of about 340nm is applied, an excimer emission appears at about 450nm and there is a smaller monomer emission at around 400nm.  When a host containing such a system binds a guest appropriately, conformational changes may occur whereby the pyrenes are unstacked.  Subsequently, the excimer emission is reduced whilst the monomer emission increases, thereby signalling the presence of a guest to the analyst.

This is mechanism is illustrated in Figure 6.

 

 

 Figure 6.  The fluorescent signalling mechanism of an optical sensor based on an intramolecular pyrene interaction.  A Guest analyte changes the optical properties of the Host by causing a conformational change.

 

Fluorescent optical sensors may have some advantages over equivalent electrochemical sensors.  They may be more sensitive and selective and from a sensor design viewpoint do not require a reference element.

 

 

Besides work for my PhD thesis, I am collaborating with colleagues on the incorporation of LEDs (Light Emitting Diodes) into sensor devices.  LEDs have the advantage that they are cheap, small, consume little power and serve as very sensitive emitters and detectors of electromagnetic radiation.

 

My career in Chemistry prior to my current position….

 

1993-1997 B. Sc. Queen’s University, Belfast (First Class Honours).

 

Having received training in general Chemistry in Queen’s, Belfast, I completed my final year project.  I synthesised large cyclic structures known as cyclophanes.  These supramolecular compounds contain a central cavity, which may selectively include a Guest (Host-Guest chemistry), according to a lock and key model (best fit).  Following the synthesis, I performed preliminary binding/quenching studies with fluorescent hosts.  This project had strong synthetic and analytical aspects and since then I have been keen to fuse aspects of analytical and organic chemistry.

 

1997-1999 M. Sc. National University of Ireland, Galway.

 

Following my degree in Chemistry, I was involved in marine chemistry research in Galway for a 2 year M.Sc.  This research primarily involved the setting up of an HPLC protocol for the analysis of marine algal pigments in water samples.  The pigment ratios observed represented a fingerprint of the type of phytoplankton present in seawater samples.  Several environmental parameters were then measured in conjunction with the pigments.  These included nutrients by colorimetric UV methods, heavy metals by AAS, salinity electrochemically, temperature and depth.  The combination of such parameters with environmental/climatic data can be particularly important for detecting and predicting the arrival of toxic blooms which affect Irish fish and shellfish aquaculture each year. 

The methods developed serve as a time and cost efficient alternative to performing phytoplankton analysis under a microscope, the traditional approach of biologists.  Apart from HPLC method development, analytical standards had to be prepared from cultured phytoplankton by preparative TLC and characterised.  Sampling was an integral part of this work as most measurements could not be performed in situ.  This ranged from the simple bottling of water for salinity measurements and sample handling for dissolved oxygen by Winkler titrations to temperature/light controlling of samples for nutrient/plankton analysis.  As with all lab based analytical research, following the development of a method, the application thereof in a commercial or field application must be the ultimate goal.  The research achieved this goal of applying a carefully developed analytical method to a real life field study.  The research carried out is particularly applicable in water/environmental chemistry.

 

2000+2001 Defelopment Chemist (permanent position). Antigen Pharmaceuticals, Co. Tipperary.

 

Antigen Pharmaceuticals (now Taro Pharmaceuticals) was a family run company in Roscrea, Co. Tipperary.  As a product development chemist, I got full training in a full range of wet chemical techniques and instrumentation relevant to the Irish pharmaceutical industry. 

The analytical instrumentation included HPLC, UV, IR, TLC, Karl Fischer moisture analyser and Osmolality testing.  Routine calibration and use of all analytical methods was a prerequisite of employment.  A thorough understanding of the functioning of all techniques was important as I was involved in training new employees in their use.  Particular attention was on HPLC where I was involved with extensive validation of analytical methods.  Part of the work routine was the introduction of new pharmaceutical products and to apply laboratory analysis techniques to them.

 I gained an insight into quality and legislative issues, Good Laboratory Practice (GLP) and the preparation of Standard Operating Procedures (SOP) for instrumentation and techniques. 

 

Publications

Publications – Ben Schazmann

 

Benjamin Schazmann, Nameer Alhashimy and Dermot Diamond.  A Chloride Selective Calix[4]arene Optical Sensor Combining Urea Functionality With Pyrene Excimer Transduction.  Journal of the American Chemical Society, full article, 2006, 128, 8607-8614. 

 http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2006/128/i26/abs/ja061917m.html

 

Benjamin Schazmann, Shane O’Malley, Kieran Nolan and Dermot Diamond.  Development of a calix[4]arene sensor for soft metals based on nitrile functionality:  relating structural tuning to an Ion Selective Electrode response.  Supramolecular Chemistry, 2006, 18, 515-522.   http://www.journalsonline.tandf.co.uk/(krxirz45tqkslji2dnd5ho45)/app/home/contribution.asp?referrer=parent&backto=searcharticlesresults,1,2;

 

TOP 5:  The above article was in the top 5 most accessed articles in Supramolecular Chemistry for 2006. http://www.informaworld.com/smpp/title~db=all~content=t713649759~tab=summary

 

Martina O' Toole, King Tong Lau, Benjamin Schazmann, Roderick Shepherd, PavelN. Nesterenko, Brett Paull and Dermot Diamond.  Novel Integrated PEDD as a Miniaturized Photometric Detector in HPLC.  The Analyst, 2006, 131, 938-943.  http://www.rsc.org/publishing/journals/AN/article.asp?doi=b602846b

 

Benjamin Schazmann, Gillian McMahon, Kieran Nolan and Dermot Diamond.  Identification and recovery of an asymmetric calix[4]arene tetranitrile derivative using liquid chromatography and mass spectrometry. Supramolecular Chemistry, 2005, 17, 393-399.  http://www.journalsonline.tandf.co.uk/(krxirz45tqkslji2dnd5ho45)/app/home/contribution.asp?referrer=parent&backto=searcharticlesresults,2,2;

  

Benjamin Schazmann and Dermot Diamond.  Improved nitrate sensing using Ion Selective Electrodes based on urea-calixarene ionophores.  New Journal of Chemistry, 2007, 31, 587-592.

 

Shane O’Malley, Benjamin Schazmann, Dermot Diamond and Kieran Nolan.  The synthesis and analytical potential of a series of phthalocyanine calixarenes and their precursors.  Tetrahedron Letters, Accepted.

 

Benjamin Schazmann, Brett Paull, Fiona Regan and Dermot Diamond.  Introducing Quality Control in the Chemistry teaching laboratory using Control Charts.  Journal of Chemical Education, Submitted.

 

 

Conference contributions

Ben Schazmann and Dermot Diamond.  The metal affinity of a series of calixarene nitriles:  mercury and silver selectivity (poster).  Development and Application of Chemical Sensors (CEAC), ETH Zurich, June 2007. 

 

S. O'Malley, B. Schazmann, D. Diamond and K. Nolan.  Synthesis of architecturally novel calix[4]arene phtalocyanines.  NCSR Away Day poster session, January 2007.

 

Ben Schazmann and Dermot Diamond.  A good combination: Chloride selectivity using a calixarene platform, urea co-ordination and pyrene optical signalling (Oral presentation).  Joint RSC meeting for Supramolecular, Coordination and Macrocycle grous, QUB Belfast, December 2006.

 

Ben Schazmann, Shane O’Malley, Kieran Nolan and Dermot Diamond.  Using ISEs to monitor changing metal affinities of a series of calix[4]arene nitriles (poster).  11^th International Conference on Electroanalysis, Bordeaux, June 2006.

 

Ben Schazmann and Dermot Diamond.  Purification by LC-MS for organic chemists: A calixarene case study (poster).  Second World Congress on Synthetic Receptors, Salzburg,  2005.

 

Ben Schazmann and Dermot Diamond.  The electrochemical properties of novel calixarene amide Supramolecular hosts (poster).  First World Congress on Synthetic Receptors, Lisbon,  2003.

 

Ben Schazmann and Dermot Diamond.  Anion Binding Studies:  Calix[4]arene Amide ISEs (poster).  Analytical Research Forum, Sunderland,  2003.

 

Ben Schazmann and Dermot Diamond.  The use of the nitrile functional group in supramolecular chemistry and electrochemistry (poster).   Zurich Electrochemistry Workshop, Switzerland, 2007.

 

Achievement Awards

 

Winner of the 2006 Colin Barnes Award for outstanding postgraduate performance in Chemistry.  Awarded 1 December 2006.

 

 

Further Information

Professional memberships:

Royal Society of Chemistry 

Irish Institute of Chemists