Thinnest X-ray detector ever created
Highly sensitive and with a rapid response time, the new X-ray detector
is less than 10 nanometres thick and could one day lead to real-time imaging of cellular biology

Date:
November 8, 2021
Source:
ARC Centre of Excellence in Exciton Science
Summary:
Researchers have created the world's thinnest X-ray detector
using tin mono-sulfide (SnS) nanosheets. Highly sensitive and
with a rapid response time, the new X-ray detector is less than
10 nanometers thick and could one day lead to real-time imaging
of cellular biology.



FULL STORY ========================================================================== Scientists in Australia have used tin mono-sulfide (SnS) nanosheets
to create the thinnest X-ray detector ever made, potentially enabling
real-time imaging of cellular biology.


========================================================================== X-ray detectors are tools that allow energy transported by radiation
to be recognised visually or electronically, like medical imaging or
Geiger counters.

SnS has already shown great promise as a material for use in
photovoltaics, field effect transistors and catalysis.

Now, members of the ARC Centre of Excellence in Exciton Science, based
at Monash Universityand RMIT University, have shown that SnS nanosheets
are also excellent candidates for use as soft X-ray detectors.

Their research, published in the journal Advanced Functional Materials, indicates that SnS nanosheets possess high photon absorption coefficients, allowing them to be used in making ultrathin soft X-ray detectors with
high sensitivity and a rapid response time.

These materials were found to be even more sensitive than another emerging candidate (metal halide perovskites), boasting a faster response time
than established detectors and are tuneable for sensitivity across the
soft X-ray region.



==========================================================================
The SnS X-ray detectors created by the team are less than 10 nanometres
thick.

To put things in perspective, a sheet of paper is about 100,000
nanometres thick, and your fingernails grow about one nanometre every
second. Previously, the thinnest X-ray detectors created were between
20 and 50 nanometres.

Considerable work remains to explore the full potential of the SnS
X-ray detectors, but Professor Jacek Jasieniak of Monash's Department
of Materials Science and Engineering, the senior author of the paper,
believes it's possible this could one day lead to real-time imaging of
cellular processes.

"The SnS nanosheets respond very quickly, within milliseconds," he said.

"You can scan something and get an image almost instantaneously. The
sensing time dictates the time resolution. In principle, given the high sensitivity and high time resolution, you could be able to see things
in real time.

"You might be able to use this to see cells as they interact. You're
not just producing a static image, you could see proteins and cells
evolving and moving using X-rays." Why are such sensitive and responsive detectors important? X-rays can be broadly divided into two types: 'Hard' X-rays are the kind used by hospitals to scan the body for broken bones
and other illnesses.



========================================================================== Perhaps less well known but just as important are 'soft' X-rays, which
have a lower photon energy and can be used to study wet proteins and
living cells, a crucial component of cellular biology.

Some of these measurements take place in the 'water window', a region of
the electromagnetic spectrum in which water is transparent to soft X-rays.

Soft X-ray detection can be conducted using a Synchrotron, a particle accelerator like the Large Hadron Collider in Switzerland, but access
to this type of hugely expensive infrastructure is difficult to secure.

Recent advances in non-synchrotron soft X-ray laser sources may allow
lower cost, portable detection systems to be designed, providing an
accessible alternative to Synchrotrons for researchers around the world.

But for this approach to work, we will need soft X-ray detector materials
that are highly sensitive to low energy X-rays, provide excellent spatial resolution, and are cost effective.

Some existing soft X-ray detectors use an indirect mechanism, in which
ionizing radiation is converted into visible photons. This approach
allows for multiple energy ranges and frame rates to be studied, but is difficult to prepare and offers limited resolutions.

Direct detection methods are easier to prepare and offer better
resolutions, because the detector material can be thinner than indirect approaches.

Good candidate materials need a high X-ray absorption coefficient,
which is calculated using the atomic number of the absorbing atoms,
X-ray incident energy, density and atomic mass of an atom.

High atomic mass and low energy X-rays favour high absorption, and
soft X-rays are more strongly absorbed in thin materials compared to
hard X-rays.

Nanocrystal films and ferromagnetic flakes have shown promise as certain
types of soft X-ray detectors, but they are not well equipped to handle
the water region.

That's where the SnS nanosheets come in.

One of the lead authors, Dr Nasir Mahmood of RMIT University, said the sensitivity and efficiency of SnS nanosheets depends greatly on their
thickness and lateral dimensions, which are not possible to control
through traditional fabrication methods.

Using a liquid metal-based exfoliation method allowed the researchers to produce high quality, large area sheets with controlled thickness, which
can efficiently detect soft X-ray photons in the water region. Their sensitivity can be further enhanced by a process of stacking the
ultrathin layers.

They represent major improvements in sensitivity and response time
compared to existing direct soft X-ray detectors.

The researchers hope their findings will open new avenues for the
development of next-generation, highly sensitive X-ray detectors based
on ultrathin materials.

First author Dr Babar Shabbir of Monash's Department of Materials Science
and Engineering said: "In the long run, to commercialise this, we need
to test a many-pixel device. At this stage we don't have the imaging
system. But this provides us with a knowledge platform and a prototype." ========================================================================== Story Source: Materials provided by ARC_Centre_of_Excellence_in_Exciton_Science. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Babar Shabbir, Jingying Liu, Vaishnavi Krishnamurthi,
R. A. W. Ayyubi,
Kevin Tran, Sherif Abdulkader Tawfik, M. Mosarof Hossain,
Hareem Khan, Yingjie Wu, Bannur Nanjunda Shivananju, Rizwan Ur
Rehman Sagar, Asif Mahmood, Adnan Younis, Md Hemayet Uddin, Syed
A. Bukhari, Sumeet Walia, Yongxiang Li, Michelle J.S. Spencer,
Nasir Mahmood, Jacek J. Jasieniak.

Soft X‐ray Detectors Based on SnS Nanosheets for the Water
Window Region. Advanced Functional Materials, 2021; 2105038 DOI:
10.1002/ adfm.202105038 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211108114824.htm

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