Nuclear magnetic resonance spectroscopy can be used to obtain structural information of molecules, their interactions, kinetics of reactions, size of spheres etc. These can be of biological origin or synthetic solutions. NMR nuclear spectroscopy is complementary to other techniques like X-ray spectroscopy, mass-spectrometry etc. Please ask for advanced experiments like- 2D-NMR, Diffusion Ordered Spectroscopy (DOSY) to study supramolecular systems, monitor reactions over time to study kinetics or perform variable temperature NMR on solutions to study dynamic processes. At Spark904 we have the following Bruker spectrometers
AV400: 5 mm BBO ATMA probe (109Ag-31P, 19F, 1H, 2H, Z gradient)
AV300II : 5mm BBOF ATMA (15N-31P and 19F, 1H,2H, Z gradient)
DRX500: 5mm BBI ATMA probe (15N-31P, 1H, 2H, Z gradient)
AV300: 5mm triple BBO probe (31P, 103Rh-31P, 1H, 2H, Z gradient)
EPR is a magnetic resonance technique very similar to NMR (Nuclear Magnetic Resonance) except that instead of measuring the nuclear transitions we measure transitions of unpaired electrons (radicals) in the sample. This is done by applying magnetic field to allow the “spin’’ of the electrons distribute themselves in two energy levels. EPR is unique in that it is the only technique that detects radicals unambiguously. EPR is also very sensitive to the local molecular environment of the unpaired electron. Additionally, even short-lived radical intermediates can be probed by using spin-trapping techniques. At Spark904 we have the capacity to using a continuous wave EPR system. For a review on applications of EPR in catalysis research see this open access paper-
EPR Spectroscopy as a Tool in Homogeneous Catalysis Research- M. Goswami, A. Chirila, C. Rebreyend and B. de Bruin, Topics in Catalysis, September 2015, Volume 58, Issue 12–13, pp 719–750.
Mass spectrometry in which m/z for each ion is measured to several decimal places (i.e., exact masses are measured, instead of nominal masses) is particularly useful to differentiate between molecular formulas having the same nominal masses. Used in combination with other spectroscopic techniques like EPR, NMR etc. high-resolution mass spectrometry can be useful in pin-pointing structural formulae of molecules. At Spark904 Mass spectra are generally collected on an AccuTOF LC, JMS-T100LP Mass spectrometer (JEOL, Japan) coupled to an ESI source or CSI source (JEOL). The special feature of the CSI apparatus is that it features a liquid nitrogen cooling device to maintain the temperature of the capillary and spray itself between 00C and - 500C. This way shot-lived intermediates or reactive, fragile supramolecular structures can be measured too.
Field desorption (FD) is also available that is adopted to ionize nonpolar molecules in vacuum residue. The FD emitter consists of a 10 μm tungsten wire onto which carbon microneedles have been grown. The emitter is about 1.5 mm away from a pair of extraction rods held at high potential (10 kV), producing very high electric fields (∼10−7–10−8 V/cm) around the tips of the carbon dendrites. Under the influence of these fields, an electron can be removed from the molecule via quantum tunneling effects, generating radical molecular ions with minimal fragmentation. Ions generated by FD are accelerated and focused into a pusher region of the TOF. Ion arrivals are recorded using a time-to-digital converter (TDC). The mass range is set at the range of 150–1400 Da. The scan duration time or spectrum accumulation time is 1 s.
SEM is an electron microscopy technique that provides detailed high resolution images of the sample by rastering a focussed electron beam across the surface. It then detects secondary and/or backscattered electron signal. SEM provides images with magnifications up to ~X50,000 allowing features to be seen which are well beyond the range of optical microscopes. What’s more, in combination with the EDX analyser, elemental identification and quantitative compositional information can be obtained. Spark904 facilitates these measurements on the FEI Verios 460 equipped with an Oxford X-Max 80 EDX system.
Typical applications of SEM-EDX are in characterization of material structures, assessment of reaction interfaces, characterization of surface defects, stains and residues on metals, glasses, ceramics and polymers, measurement of the thickness of layered structures, metallised layers, oxide films, composite materials using cross sectional imaging, contaminant analysis on and within materials etc.
When chiral compounds are liquids or oils, or exist in various conformations, it can be challenging to determine their absolute configurations. This information is, however, very important, especially in pharmaceutical applications, peptide chemistry etc. VCD is a technique that gives you the absolute configuration of a molecule (R or S enantiomer). It is similar to circular dichroism (CD) but then extended to Infra-Red and near Infra-Red region. Because VCD is sensitive to the mutual orientation of distinct groups in a molecule, it provides three-dimensional structural information, even in a mixture of differently oriented molecules. Moreover, we are also able to simulate the VCD spectra of enantiomers can ab initio calculations, thereby allowing the identification of absolute configurations of small molecules in solution from VCD spectra.
Both, acquisition and analysis of VCD spectra can be done at Spark904.
Infrared (IR) absorption by molecules correlates to their differences in vibration energy, which in turn correlates to polarity of the bonds they make. Thus, IR spectroscopy can be very useful to probe polar functional groups in molecules and materials; most of them have finger-print regions in which they absorb IR radiation.
For coloured molecules, the absorption or reflectance in the visible range can be directly measured using UV-vis spectrometers. Because of the ease of performing UV-vis spectroscopy, the corresponding bands can be followed in time to perform kinetic measurements on reaction progress.
At Spark904 we can perform IR and UV-vis measurements as a characterisation tool for molecules as well as to study the progress of chemical reactions.
Photoluminescence, often loosely called fluorescence, is the emission of light by a sample that results from excitation with light. It can be used as an analytical tool for materials ranging from crude oils to biological samples to luminescent sensors for specific analytes and many more.
Spark904 provides access to several instruments that can measure the spectra and excited state lifetimes of samples over a wide variety of wavelengths and time scales.
Using confocal fluorescence microscopy, samples can be imaged in three dimensions with diffraction limited resolution, that is, about 300 nanometers in the imaging plane, and about a micrometer in the axial direction. In each volume element additional information can be obtained such as lifetime, anisotropy and spectrum. The Picoquant Microtime 200 microscope is equipped with two laser light sources that allow practically any wavelength in the visible range to be used.
Also referred to as inductively coupled plasma optical emission spectrometry (ICP-OES), it is an analytical technique used for the detection of chemical elements at ppm levels. It is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions from the elements present in a sample. These excited atom/ions emit electromagnetic radiation at wavelengths characteristic of a particular element, just as the chemicals in fireworks! It is the intensity of this emission that is indicative of the concentration of the element within the sample.
The applications of these technique are varied- ranging from determination of metals in wine, trace metals bound to protein, to find data on various streams in mineral processing, trace elements in soil, etc.
For information on the available surface area of your material, BET measurements can performed. BET is a theory or method to determine surface areas but doesn’t give any direct information about porosity of the materials. It is from N2 adsorption at 77K that one can determine most of the parameters needed when full isotherms are measured (from about 0 to about 1 p/p0). Micropore sizes can be obtained from other theories other gasses (CO2 at 273K). Gas adsorption methods will also not give you direct information about bulk or apparent densities.
Hg intrusion can be used to measure pore sizes down to about 3.5 nm. It is based on Laplace's equation for capillary pressure, and therefore theoretically gives you only the size of the largest entrance to a pore. Hg intrusion does not give direct information about areas or morphologies. A combination of these techniques are often essential to get useful information.
At Spark904 we are able to perform surface areas and isotherms (N2 and CO2) and porosimetry (both N2 and Hg).
Applications include heterogeneous catalysts, carbons, metal powders, ceramics, active pharmaceutical ingredients (APIs), construction materials, solid foams etc.
Gas Pycnometery is typically used to determine the true volume and true density of powders and bulk solidsThe true volume of a solid is calculated from the measured drop in pressure when a known amount of gas is allowed to expand into a chamber containing the sample. Thus, it excludes any pore volume accessible to the gas. Helium is the preferred gas, because it exhibits ideal gas behavior. The helium pycnometer measures the true volume and density of solid powders. Should be fully automatic, provide high-speed, high-precision volume measurements and density calculations.
The other fluid used is mercury. Since mercury does not wet many of the materials and requires pressure to enter the pores of the material, at atmospheric pressure, mercury cannot enter pores that are smaller than about 15 microns. Therefore, the weight of mercury in a sample chamber of known volume, containing a sample of known weight, is used to compute bulk density of the sample.
At Spark904 we are able to perform both He and Hg pycnometry.
While studying materials, it is often useful to see how the physical properties change as a function of temperature. Several methods can be used. At Spark904 we are able to provide you with:
Differential Scanning Calorimetry (DSC)- In this technique the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment. This is routinely used for analysis of polymers, liquid crystals, oxidative stability, safety screening and in general chemical analysis.
Temperature range- -20 ◦C to 700 ◦C
Thermogravimetric analysis or thermal gravimetric analysis (TGA)- It is a method of thermal analysis where the mass of a sample is measured over time as the temperature changes. TGA is routinely used to study physical phenomena, such as phase transitions, absorption and desorption; as well as chemical phenomena including chemisorptions, thermal decomposition, etc.
Temperature range possible- Up to 1000 ◦C
MALDI-MS (Matrix Assisted Laser Desorption Ionization) is a technique where molecules are ionized by laser, in a so-called “soft ionization” process. This technique allows the formation of single-charged ions and can be applied in a wide range of substances, from drugs to intact antibodies.
It can also be applied to samples that cannot be analyzed by other techniques such as ESI-MS. The experiments can be performed at high resolution mode (for molecules up to 6kDa) or at regular spectral resolution for intact larger molecules, providing their nominal masses. Also, molecular fragmentation experiments (MS/MS) can be done to provide a more accurate analyte identification.