Silicon micro-levers and a multilayer graphene membrane studied via laser photoacoustic detection

Abstract

Abstract. Laser photoacoustic spectroscopy (PAS) is a method that utilizes the sensing of the pressure waves that emerge upon the absorption of radiation by absorbing species. The use of the conventional electret microphone as a pressure sensor has already reached its limit, and a new type of microphone -an optical microphone -has been suggested to increase the sensitivity of this method. The movement of a micro-lever or a membrane is sensed via a reflected beam of light, which falls onto a position-sensing detector. The use of one micro-lever as a pressure sensor in the form of a silicon cantilever has already enhanced the sensitivity of laser PAS.Herein, we test two types of home-made sensing elements -four coupled silicon micro-levers and a multilayer graphene membrane -which have the potential to enhance this sensitivity further. Graphene sheets possess outstanding electromechanical properties and demonstrate impressive sensitivity as mass detectors. Their mechanical properties make them suitable for use as micro-/nano-levers or membranes, which could function as extremely sensitive pressure sensors.Graphene sheets were prepared from multilayer graphene through the micromechanical cleavage of basal plane highly ordered pyrolytic graphite. Multilayer graphene sheets (thickness ∼ 10 2 nm) were then mounted on an additional glass window in a cuvette for PAS. The movements of the sheets induced by acoustic waves were measured using an He-Ne laser beam reflected from the sheets onto a quadrant detector. A discretely tunable CO 2 laser was used as the source of radiation energy for the laser PAS experiments. Sensitivity testing of the investigated sensing elements was performed with the aid of concentration standards and a mixing arrangement in a flow regime. The combination of sensitive microphones and micromechanical/nanomechanical elements with laser techniques offers a method for the study and development of new, reliable and highly sensitive chemical sensing systems. To our knowledge, we have produced the first demonstration of the feasibility of using four coupled silicon micro-levers and graphene membranes in an optical microphone for PAS. Although the sensitivity thus far remains inferior to that of the commercial electret microphone (with an S/N ratio that is 5 times lower), further improvement is expected to be achieved by adjusting the micro-levers and membrane elements, the photoacoustic system and the position detector.

Cantilever-Enhanced Photoacoustic Detection and Infrared Spectroscopy of Trace Species Produced by Biomass Burning

“…In the optical microphone, a second laser was used for the detection of the movement of the cantilever. The laser beam reflected from the surface of the cantilever is aimed onto a position-sensitive detector (see refs , , and for more details). The GASERA software collects the harmonic components of the measured signal (i.e., performs the Fourier transformation).…”

A Review of Acoustic Devices Based on Suspended 2D Materials and Their Composites

“…Zelinger et al developed a method (Figure 11b) that utilizes a silicon cantilever coupled with a multilayer graphene film, employing similar principles as the atomic force microscopy (AFM) tip. [213] This method allows direct analysis of vibrations from beam reflection signals. However, the sensitivity and signal-to-noise ratio (SNR) of this method have not been proven to be more precise than acoustic detection using high-quality microphones.…”

Direct Absorption and Photoacoustic Spectroscopy for Gas Sensing and Analysis: A Critical Review

“…A comparison of the performance of a graphene‐based cantilever and condenser microscope was reported by Zelinger et al. [ 187 ] The authors developed a multilayer graphene membrane and a multilayer graphene cantilever that were more sensitive than commercially available condenser microphones. Methanol was measured, and the detection limit was around 420 and 330 ppb for the membrane and cantilever, respectively as compared to 750 ppb for a commercial condenser microphone.…”