Solid State NMR Spectrometer

   The Bruker Avance NEO 500 is a Nuclear Magnetic Resonance (NMR) spectrometer specifically equipped for high-resolution studies on solid systems, with a Magic Angle Spinning (MAS) device and three High-Power radiofrequency (RF) amplifiers (>500 W RF peak power, one for 1H/19F and two broadband from 15 to 600 MHz).
It operates at a static magnetic field of 11.7 T, corresponding to a Larmor frequency for 1H nuclei of 500 MHz, generated by a superconducting narrow bore (ø 54 mm) magnet Bruker Ascend, with anti-vibration and electromagnetic disturbance suppression apparatuses, helium and nitrogen level sensors.
Three independent radiofrequency channels are present: one dedicated to 1H and 19F nuclei, and two to the remaining nuclei (¹³C, ²H, ²⁹Si, ³¹P, ¹⁵N, ²⁷Al, ²³Na, ²⁰⁷Pb, ¹⁰⁹Ag, ¹⁹⁵Pt, etc.).
Each of the three radiofrequency channels includes TRX1200, a highly integrated NMR radiofrequency transceiver (transmit and receive) unit with a built-in pulse program engine (sequencer, waveform memory) providing: RF signal bandwidth of 5 to 1200 MHz for transmit and receive; timing resolution of 12.5 ns; simultaneous RF amplitude, phase & frequency setting within 12.5 ns; high speed Analog-to-Digital Converter (ADC) with 240 MSPS @16 Bit, Digital Down Converter (DDC); high speed Digital-to-Analog Converter (DAC) with 960 MSPS, Digital Up Converter (DUC); high intermediate frequency (IF) for transmit and receive of 1852 MHz (e.g. no unwanted LO windows); sequencer waveform memory 1GB (e.g. pulse shaping, optimal control applications, composite pulse decoupling); spectral width up to 7.5 MHz; effective dynamic range >17 Bit (5 MHz) / >19 Bit (1 MHz) / >23 Bit (6 kHz).
The variable temperature apparatus is constituted by a BCU II cooler and a membrane air dryer providing air with a dew point below -80 °C.
An integrated lock RF transceiver (L-TRX, transmit and receive unit) with incorporated 5W radiofrequency amplifier for field lock operation on deuterated solvents is present for use with the HRMAS probe.


Probes

The spectrometer is equipped with five different probes:

• double-channel (H/F-X) CPMAS probe with outer rotor diameter of 1.3 mm. X channel tunable from ³¹P to ¹⁵N. ¹H to ¹⁹F high power decoupling. Temperature range from -30 °C to 70 °C. Maximum MAS frequency 67 kHz;
• triple-channel (H-X-Y) CPMAS probe with outer rotor diameter of 2.5 mm. X channel tunable for predefined nuclei in the range ³¹P to ¹³C. The tuning range of the Y channel is determined by the frequency of the X channel: highest Y-frequency ²³Na, lowest Y-frequency ¹⁵N. ¹H high power decoupling. Temperature range from -50 °C to 80 °C. Maximum MAS frequency 35 kHz;
• double-channel (H/F-X) CPMAS probe with outer rotor diameter of 4.0 mm. X channel tunable from ³¹P to ¹⁵N. ¹H to ¹⁹F high power decoupling. Temperature range from -50 °C to 80 °C. Maximum MAS frequency 15 kHz;
• double-channel (H/F-X) CPMAS probe with outer rotor diameter of 3.2 mm. X channel tunable from ¹⁵N to ¹⁰⁹Ag. ¹H to ¹⁹F high power decoupling. Temperature range from -50 °C to 80 °C. Maximum MAS frequency 24 kHz;
• triple-channel (H-C-P) HRMAS probe with outer rotor diameter of 4.0 mm. Optimized for 1H observation. Optimized for ¹³C and/or ³¹P decoupling and suitable for ¹³C and ³¹P observation. ²H lock
single axis angle gradient along the magic angle, 5 G/cm*A.
Temperature range from -20 °C to 80 °C. Maximum MAS rotation frequency 15 kHz.

Applications

The information that can be obtained includes, but is not limited to:
– chemical structure of insoluble or scarcely soluble materials;
– conformational and phase properties;
– inter-molecular interactions;
– composition and dimensions of interfaces;
– average domain dimensions on a nanometric scale;
– polymorphism and heterophasicity;
– crystallinity degree;
– structural and dynamic order/disorder;
– details on molecular motions on a wide frequency scale (Hz-GHz).
Such information can be obtained on solid materials ranging from crystalline to amorphous, on soft materials (gels, liquid crystals), as well as on individual phases of heterophasic materials.
Almost all kinds of materials can be investigated, as, for example, polymers, biopolymers, drugs, silicates, cements, zeolites, perovskites, MOFs, hybrid organic-inorganic materials, organometallics, elastomers, ionic liquids, liquid crystals, etc.

Key benefits

– all kinds of mono- and multi-dimensional NMR experiments requiring last-generation and highly performant electronics can be carried out;
– simultaneous observation of different nuclei and, in particular, the possibility to perform triple-channel experiments;
– application of state-of-the-art high-power hetero- and homo-nuclear decoupling techniques to improve spectral resolution;
– observation of scarcely sensitive nuclei of the periodic table characterized by low-gyromagnetic ratios (²⁵Mg, ⁸⁹Y, ¹⁰⁹Ag, etc.), important in several technological applications.
– using very high MAS frequencies (up to 67 kHz), allowing a striking improvement of spectral resolution in many situations.