KR101096098B1 - Laser Desorption/Ionization Method Using Nanowire - Google Patents

Abstract

The present invention relates to a laser desorption / ionization mass spectrometry method using nanowires. In detail, the mass spectrometry method according to the present invention is a mass arranged on a plurality of nanowires that are arranged perpendicular to a substrate and satisfy the following Equation 1 and Equation 2 below. After placing the sample to be analyzed, the nanowires on which the sample is located are irradiated with a laser and desorption / ionization of the sample is characterized by analyzing the mass of the sample.
(Relationship 1)
0.8 x D _pe <D _nw <D _ch
(Relationship 2)
D _ch <L _nw <10xS _nw
(D _nw is the uniaxial diameter of the nanowire, L _nw is the long axis length of the nanowire, the D _ch is the depth of Conductive Heating of the nanowire during laser irradiation, D _pe is nano The penetration depth of laser in the wire, S _nw is the shortest separation distance between nanowires relative to the surface of the nanowires in a plurality of nanowires arranged vertically on the substrate.)

Description

Matrix free mass spectrometry using nanowires {Laser Desorption / Ionization Method Using Nanowire}

The present invention relates to a laser desorption / ionization mass spectrometry method using nanowires, which does not use a matrix, has a very high desorption / ionization efficiency, and can effectively analyze materials having a molecular weight of 1,000 Daltons (Da) or less. To a matrix-free mass spectrometry method.

MALDI (Matrix-Assisted Laser Desorption / Ionization), a very powerful mass spectrometry, instantly irradiates a biochemical polymer analyte into a gaseous state by irradiating UV lasers to crystals containing peptides and proteins of high molecular weight together with matrix molecules. It is a method of measuring the molecular weight or analyzing the structure by mass spectrometry by releasing ions. In other words, by dispersing and diluting a nonvolatile sample with matrix molecules, such as biochemical polymers, which are ultraviolet absorbers, crystals are formed, followed by irradiation with a strong pulsed UV laser to induce desorption / ionization from the crystals. The molecular weight of the released sample molecules ions is measured or the structure is analyzed using tandem mass spectrometry. Although MALDI has a strong merit of picomol level analysis in femtomol and ionizing polymer biochemicals that are difficult to make into gas ions, the selection of an appropriate matrix according to the type of sample and the optimization of crystal condition are performed. This will have a big impact. In addition, since the matrix crystals are not formed on a regular basis, when irradiating a laser to a so-called hot spot, a strong intensity ion signal necessary for mass spectrometry can be obtained, but ions are well formed at another position of the sample crystal. Reproducible measurements are difficult to expect, which makes quantitative analysis difficult and difficult to implement mass imaging such as chemical mapping. In addition, biomolecularly low molecular weight substances of less than 700 Daltons (Da), such as drugs, metabolites, lipids, and the like have a disadvantage in that measurement is difficult due to interference by matrix ion peaks.

To solve these problems, mass spectrometry has been attempted by laser desorption / ionization of low molecular weight materials using nanostructures without using a matrix (Guo, Z .; Ganawi, AAA; Liu, Q .; He, L Nanomaterials in Mass Spectrometry Ionization and Prospects for Biological Applications.Anal.Bioanal.Chem. 2006, 384, 584.592.)

Whether various nanostructures can be used for Surface-Assisted Laser Desorption / Ionization (SALDI), and their potential, are being tested, for example, Au, Al, Mn, Sn, Attempts have been made to replace matrices with nano and micrometer sized particles such as W, Si, Sn, SnO ₂ , TiO ₂ , and ZnO (McLean, JA; Stumpo, KA; Russell, DH Size-Selected) (2.10 nm) Gold Nanoparticles for Matrix Assisted Laser Desorption Ionization of Peptides.J. Am. Chem. Soc. 2005, 127, 5304-5305 .; Desorption / Ionization Time-of-Flight Mass Spectrometry Using An Inorganic Particle Matrix for Small Molecule Analysis.J. Mass Spectrom. 2000, 35, 417-422 .; Lee, K.-H .; Chiang, C.-K .; Lin, Z.-H .; Chang, H.-T. Determining Enediol Compounds in Tea Using Surface-Assisted Laser Desorption / Ionization Mass Spectrometry with Titanium Dioxide Nanoparticles Matrices.Rapid Commun.Mass Spectrom. 2007, 21, 2023-2030. ; Watanabe, T .; Kawasaki, H .; Yonezawa, T .; Arakawa, R. Surface-Assisted Laser Desorption / Ionization Mass Spectrometry (SALDI-MS) of Low Molecular Weight Organic Compounds and Synthetic Polymers Using Zinc Oxide (ZnO) Nanoparticles . J. Mass Spectrom. 2008, 43, 1063-1071.

Desorption Ionization on Porous Silicon (DIOS) is a well-known method of using a laser as a desorption / ionization energy source for analyte, but without using a matrix (Wei, J .; Buriak, JM; Siuzdak, G. Desorption-Ionization Mass Spectrometry On Porous Silicon.Nature 1999, 399, 243-246 .; Shen, Z .; Thomas, JJ; Averbuj, C .; Broo, KM; Engelhard, M .; Crowell, JE; Finn, MG; Siuzdak, G. Porous Silicon as a Versatile Platform for Laser Desorption / Ionization Mass Spectrometry.Anal.Chem. 2001, 73, 612-619.), Based on Si nanowires, Si nanoparticles and various Si nanostructure surfaces. Laser desorption / ionization mass spectrometry has been tried.

In addition to Si, ZnO nanoparticles and ZnO nanowires have also been reported to effectively replace matrices in laser desorption / ionization (Watanabe, T .; Kawasaki, H .; Yonezawa, T .; Arakawa, R. Surface- Assisted Laser Desorption / Ionization Mass Spectrometry (SALDI-MS) of Low Molecular Weight Organic Compounds and Synthetic Polymers Using Zinc Oxide (ZnO) Nanoparticles.J. Mass Spectrom. 2008, 43, 1063-1071.).

However, nanostructures including porous silicon, nanowires, and nanoparticles used in DIOS are supposed to absorb laser energy like the matrix and cause ionization of the sample.However, the accurate energy transfer path for desorption / ionization of the sample is possible. Although not known, many researches have been conducted on semiconductor materials such as Si, nanostructure materials such as noble metals and metal oxides, which can effectively replace matrices. Little research has been done on the structure of nanostructures that enable ionization.

Applicants have conducted numerous experiments on laser desorption / ionization mass spectrometry using nanowires, and surprisingly, the dimensions of the nanowires have a very significant effect on the laser desorption / ionization efficiency. The very high laser desorption / ionization efficiency increased significantly, resulting in mass spectrometry of the material with extremely high sensitivity, and finding a material with a very small molecular weight stably and reproducibly with extremely good SNR. .

The object of the present invention is not to use a matrix, have a very high desorption / ionization efficiency, a very good signal to noise (SNR), mass that can effectively analyze materials having a molecular weight of less than 1000 Daltons (Da) It is to provide an analysis method.

In the matrix-free mass spectrometry method using nanowires according to the present invention, after placing a sample, which is a mass spectrometry material, on a plurality of nanowires arranged vertically on a substrate and satisfying Equation 1 and Equation 2 below, the sample is located nano The laser is irradiated to the wire, and the sample is desorbed and ionized to analyze the mass of the sample.

(Relationship 1)

0.8 x D _pe <D _nw <D _ch

(Relationship 2)

D _ch <L _nw <10xS _nw

(D _nw is the uniaxial diameter of the nanowire, L _nw is the long axis length of the nanowire, the D _ch is the depth of Conductive Heating of the nanowire during laser irradiation, D _pe is nano The penetration depth of laser in the wire, S _nw is the shortest separation distance between nanowires relative to the surface of the nanowires in a plurality of nanowires arranged vertically on the substrate.)

In the analysis method of the present invention, the nanowires vertically arranged on the substrate mean nanowires having vertical alignment with respect to the surface of the substrate on which the nanowires are formed, and the vertical alignment indicates the length of the nanowires in the vertical and horizontal directions. When decomposed into components, it means that the vertical component of the substrate is larger than the horizontal component of the substrate. The verticality of the vertical arrangement may not be limited to the vertically strict mathematical sense, and includes nanowires partially deviated from the vertically strict meaning by the manufacturing process and gravity of the nanowires.

In the analysis method of the present invention, the nanowires include silica, an oxide containing zinc oxide, a Group 4 element including silicon, or a Group 3-5 compound including silicon-germanium, wherein the nanowires are monocrystalline. , Polycrystalline or amorphous nanowires. In this case, in view of the effective absorption of laser energy, the nanowires are preferably monocrystalline or amorphous nanowires.

In the analysis method of the present invention, mass spectrometry of a sample (analyte to be desorbed / ionized) by laser irradiation may be performed using a conventional mass spectrometer which analyzes the mass of the ionized material, The mass spectrometer includes a time of flight mass spectrometer.

In the analytical method of the present invention, the location of the sample to be mass spectrometry on the nanowire includes that the sample is adsorbed and fixed on the surface of the nanowire.

In the analysis method according to the present invention, the nanowires are characterized by being zinc oxide (ZnO) nanowires, preferably monocrystalline zinc oxide nanowires, wherein the laser is ultraviolet (UV) and the D _ch is 100 to 150 nm. Irradiated to the nanowires such that S _{nw, which} is a distance between the nearest nanowires of the plurality of nanowires vertically arranged on the substrate, satisfies 30 to 36 nm, and the nanowires are represented by Equation 3 and Equation 4 below. There is a satisfying feature.

(Relationship 3)

45nm <D _nw <55nm

(Relationship 4)

200nm <L _nw <300nm

In addition, in the analysis method according to the present invention, a threshold laser power that satisfies a signal to noise ratio (SNR) of 100 in mass analysis by desorption / ionization of the sample is replaced by the nanowires and thus mass. 0.5 to 0.8 times the threshold laser power, which satisfies the signal to noise ratio (SNR) of 100 of a single crystal substrate of the same material as the nanowire to be analyzed, characterized in that the laser is a plurality of nanowires Is characterized in that it is irradiated at an angle of 20 ° to 40 ° with respect to the vertical direction of the substrate surface arranged.

In carrying out the analytical method according to the present invention, after the mass analysis target is dissolved or dispersed in a liquid medium in contact with the analyte solution and the nanowires, the liquid medium is removed to remove the mass from the nanowires. It is preferable to position the sample to be analyzed, and the contacting is more preferably performed by dropping the droplets of the analyte on the nanowires, and the concentration of the mass spectrometry contained in the analyte is preferably 100 fmol to 100 pmol. Do.

More specifically, in the analysis method of the present invention, the mass spectrometry object has a molecular weight of 200 to 800 Daltons (Da).

The analytical method of the present invention has the advantage of having an extremely high desorption / ionization efficiency, a very good signal to noise (SNR), and a material having a molecular weight of 1000 Daltons (Da) or less.

1 is a scanning micrograph of zinc oxide nanowires vertically oriented on a substrate spaced apart from each other, a) to f) are scanning electron micrographs of nanowires having a length of 50 nm to 1600 nm,
FIG. 2 is a diagram illustrating an X-ray diffraction pattern of the zinc oxide nanowires of FIG. 1.
FIG. 3 shows SALDI mass spectra of analyte (a) Clonidine, b) Azithromycin, c) Tamoxifen, d) ketoconazole, located on zinc oxide nanowires 250 nm long. Is a view showing
4 is a diagram showing the threshold laser power according to the length of the zinc oxide nanowires and the ionic strength at a specific laser power, a) shows the threshold laser power according to the length of the zinc oxide nanowires based on the SNR of 100. And b) shows the ionic strength along the length of the nanowires at 48% laser power.
FIG. 5 shows the concentration of Clodinine (a) 100 fmol, b) 1 pmol, c) 10 pmol, d) 100 in a 220 nm long zinc oxide nanowire using Clonidine as a detection target material. pmol) according to the ion detection intensity,
FIG. 6 is a scanning electron micrograph (a) of a 250 nm long zinc oxide nanowire in which clonidine is located (en) and energy dispersive spectroscopy of elements of Zn (b), O (c), and Cl (d), respectively. ) Is a diagram showing the mapping,
FIG. 7 shows a scanning electron micrograph (a) of a 2.6 μm long zinc oxide nanowire in which clonidine is located and EDS mapping for each element of Zn (b), O (c), Cl (d). One drawing.

Hereinafter, the analysis method of the present invention will be described in detail. Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

The analytical method according to the present invention uses a plurality of nanowires (nanowire arrays) oriented perpendicular to a substrate without using a conventional matrix, and then places the analyte on the nanowire, and then places the analyte thereon. Surface assisted laser desorption ionization, which irradiates a laser onto the nanowire, desorbs and analytes the analyte by the energy of the laser absorbed by the nanowire, and analyzes the ionization mass (m / z) of the desorbed analyte. (SALDI; Surface-Assisted Laser Desorption / Ionization, hereinafter referred to as SALDI).

In particular, the analytical method according to the present invention maximizes absorption of laser energy by controlling nanowires vertically oriented to the substrate surface and rapidly increases desorption / ionization efficiency of analyte by transfer of absorbed energy. There is a characteristic.

As described above, no research has been conducted on the effect of the structure itself of the nanostructures (including nanowires) replacing the matrix on laser desorption / ionization.

Applicants have deepened their research on nanostructures that effectively replace matrices and can also analyze low molecular weight biochemicals with very high sensitivity, and found that nanowire lengths have a profound effect on laser desorption / ionization. It can be seen that a rapid increase in laser desorption / ionization efficiency occurs at the nanowire thickness and nanowire length under certain conditions.

In detail, FIG. 1 illustrates a scanning electron microscope of ZnO nanowires of various lengths prepared by using a vapor phase transfer method using Au / Ti formed on a Si substrate as a catalyst. For more information on the preparation of ZnO nanowires, see Shin et al. (Shin, JH; Song, JY; Park, HM Growth of ZnO Nanowires on a Patterned Au Substrate. Mater. Lett. 2009, 63, 145- 147.).

By controlling the growth time of the nanowires to prepare nanowires having different lengths, it was confirmed that the different lengths of nanowires have a similar short axis diameter of 40 to 60nm (50nm ~ 10nm). The prepared nanowires have a length of 25 nm to 1600 nm, and examples of the prepared nanowires are illustrated in FIGS. 1 (a) to 1 (f).

As a result of analyzing the prepared nanowires, it was confirmed that a single nanowire was composed of a single single crystal. As can be seen from the X-ray analysis result shown in FIG. 2, zinc oxide nanowires having a WZ (wurztite) crystal structure were obtained. It was confirmed that a plurality of zinc oxide nanowires were prepared and oriented perpendicular to the substrate surface in the [001] direction of the major axis. In this case, Si in FIG. 2 is a peak due to the Si substrate on which the nanowires are grown.

The nanowire density on the substrate surface was 1.5 × ^{10 10} / cm ⁻² , and the distance between the nanowires with respect to the surface of the nanowires (ie, the length of the nanowires closest to the one nanowire at the long axis of one nanowire). Shortest distance to the long axis surface) was 30-36 nm in average.

In addition, photoluminescence experiments were performed on nanowires of 50 nm length and nanowires of 250 nm length, and the same photoluminescence properties were obtained on the two nanowires. The photoluminescence properties of bulk monocrystalline zinc oxide were obtained. It was confirmed that the same as. As a result, it can be seen that the nanowires having the same physical properties as those of the zinc oxide in the bulk state are produced without changing the physical properties of the zinc oxide in the nanostructure as in the quantum confinement effect.

As analyte, Clonidine (exact mass: 230.1 Da, Sigma Aldrich), azithromycin (exact mass: 749.0 Da, Sigma Aldrich), tamoxifen (Taxixi, exact mass: 371.5 Da) , Sigma Aldrich) or ketoconazole (exact mass: 531.4 Da, Sigma Aldrich) were used.

In order to place the analyte on a plurality of nanowires vertically oriented on the substrate, the analyte (10 analyte concentration: 5 pmol) was added to ultrapure water mixed with 10% by volume of analyte to 10 μM. After the preparation, 0.5 μL of analyte droplets were dropped on the nanowires and then dried. Mass spectrometry was performed using a MALDI mass spectrometer (Matrix-Assisted Laser Desorption / Ionization mass spectrometer) (Autoflex III; Bruker-Daltonics, Bremen, Germany) with a UV laser (emission wavelength 355 nm). The laser power irradiated to the nanowire is described in% based on the maximum laser power.The measurement was repeated at least four times, and the average value was taken as a result of mass analysis. It was.

Figure 3 shows the SALDI mass spectrum obtained for each analyte using a 250 nm long zinc oxide nanowire, Figure 3 (a) is clonidine, Figure 3 (b) is azithromycin, Figure 3 (c) shows tamoxifen, and FIG. 3 (d) shows ketoconazole as an analysis target material.

As can be seen in Figure 3, when the matrix is replaced with 250 nm long zinc oxide nanowires, it can be seen that the unbreakable molecular ion of a strong signal strength is generated. In this case, the charge required in the ionization process is obtained from cationization or protonation of Na ⁺ or Ka ⁺ remaining from the sample solution, the environment, or the synthesis step of the nanowire, and other ion peaks shown in the mass spectrum. They originate from the contamination of the sample rather than the daughter ions broken out of the sample.

The mass spectrum of FIG. 3 is dipped with an analyte (5 pmol) containing an analyte (sample) on a 250 nm long zinc oxide nanowire, having a diameter of about 1 mm on a substrate. It is about 4.7x10 ¹³ cm ^-2 . This is less than 10 ¹⁵ , which is the typical surface density, and it is estimated that sample molecules located on the surface of the nanowire will not go beyond the monolayer.

4 is a diagram showing the critical laser power according to the length of the zinc oxide nanowires and the ionic strength at a specific laser power, Figure 4 (a) is a view showing the critical laser power along the length of the zinc oxide nanowires, 4 (b) shows ionic strength along the length of the nanowires at 48% laser power.

In this case, the threshold laser power is a near-threshold laser power, and means a laser power at which a signal to noise ratio (SNR) 100 is obtained.

As shown in FIG. 4 (a), it can be seen that the ion yield of the nanowires absorbing the energy of the laser and transmitting the absorbed energy to desorb and ionize the material to be analyzed has a distinct dependence on the length of the nanowires. In addition, it can be seen that the ion yield is rapidly increased in the nanowire of 200 to 300nm length.

The same experiment was performed on a (0001) surface single crystal zinc oxide substrate (MIT corporation) for comparison, and the critical laser power for the single crystal zinc oxide substrate was determined to be 1.5 times higher than that of 250 nm long zinc oxide nanowires.

Furthermore, as shown in FIG. 4 (b), the ion yield was measured using a fixed laser power of 48% for nanowires of different lengths, and as a result, the most efficient mass spectrum was obtained in nanowires of 250 nm length. It was confirmed that there is. At this time, the 48% laser power is sufficiently higher than the critical laser power.

In detail, as can be seen in Figure 4 (b), for all four different analytes, although the molecular weight of the analyte is very low molecular weight of 230 to 750 Daltons (Da), it is remarkable in the nanowire of 250nm length It can be seen that a high laser desorption ionization efficiency is obtained.

5 is a nanowire having a length of 220 nm and using Clodinin as an analyte, 100 fmol (FIG. 5 (a)), 1 pmol (FIG. 5 (b)), 10 in analyte concentration of analyte. Figure 5 shows the mass spectrum measured by adjusting to pmol (Fig. 5 (c)) and 100 pmol (Fig. 5 (d)), respectively. As can be seen in FIG. 5, the sensitivity of laser desorption ionization (SALDI) at 220 nm length, which belongs to the nanowire length, in which the ion yield rapidly increases, was evaluated as much better than 100 fmol.

These results indicate that the physical structure of the nanostructures is very important in laser desorption ionization, and show that nanowires that meet specific size conditions cause laser desorption ionization very effectively.

FIG. 6 is a scanning electron micrograph (a) of a 250 nm long zinc oxide nanowire in which clonidine is located (en) and energy dispersive spectroscopy of elements of Zn (b), O (c), and Cl (d), respectively. 7 shows a scanning electron micrograph (a) and Zn (b), O (c), and Cl (d) of a 2.6 μm long zinc oxide nanowire on which Clodinine is located. A diagram showing EDS mapping for elements of. As shown in FIG. 6 to FIG. 7, the distribution of the analyte to be located in the nanowires using EDS shows that the sample is evenly adsorbed in the longitudinal direction of the nanowires.

Based on the results of FIGS. 1 to 5, when performing laser desorption ionization mass spectrometry using a plurality of nanowires oriented perpendicular to the substrate surface, by using nanowires satisfying the following relations 1 and 2, It is possible to remarkably increase the efficiency of laser desorption / ionization, perform mass spectrometry of materials with extremely high sensitivity, and find very stable and reproducible detection of materials with very small molecular weight with very good SNR. have.

(Relationship 1)

0.8 x D _pe <D _nw <D _ch

(Relationship 2)

D _ch <L _nw <10xS _nw

(D _nw is the uniaxial diameter of the nanowire, L _nw is the long axis length of the nanowire, the D _ch is the depth of Conductive Heating of the nanowire during laser irradiation, D _pe is nano The penetration depth of laser in the wire, S _nw is the shortest separation distance between nanowires relative to the surface of the nanowires in a plurality of nanowires arranged vertically on the substrate.)

The very low critical laser power in nanowires with specific lengths and specific short axis diameters means that the nanostructures contribute to the effective absorption of the laser and the effective transfer of this energy back to the adsorbed molecules.

As shown in the mass spectrometry of FIGS. 3 to 5, in the case of zinc oxide, a depth of conductive heating = (kt / Cpπ) ^0.5 when the laser irradiation time is 7 ns, k = thermal conductivity of the nanowire material, Cp = heat capacity of the nanowire material, t = laser irradiation time) is 130 nm.

For nanowires satisfying Equation 1, the depth of conductive heating is greater than the diameter of the nanowires, and the lateral heat conduction is limited by surface boundary conditions and absorbs 355 nm laser energy. The penetration depth of the laser (1 / a = 60 nm) is comparable to the diameter of the nanowires. The irradiated laser energy is efficiently generated through the entire nanowire. The energy accumulated in the nanowires contributes to the increase of the surface temperature during the laser desorption ionization and thus the desorption of molecules. For example, it has been reported that the surface temperature can be increased above 1000 K due to instantaneous surface heating by UV laser absorption.

As shown in Equation 2, when the length of the nanowire is longer than the depth of conductive heating, the loss of the laser energy absorbed from the nanowire through the substrate is minimized, effectively increasing the surface temperature of the nanowire. .

As such, the irradiated laser energy is effectively absorbed and heated in the entire short axis diameter of the nanowire, and in order to minimize the loss of energy absorbed at the interface with the outside, the relation 1 must be satisfied, and the absorbed energy toward the substrate direction. In order to minimize the loss, the length of the nanowires should be longer than the depth of conductive heating, as shown in Equation 2 above.

In addition, after placing the analyte on a plurality of nanowires vertically oriented to the substrate, as the laser is irradiated, relation 2 may be satisfied by structural effects related to the array of nanowires positioned on the substrate.

Specifically, as the nanowires efficiently absorb the laser energy, they can mask the laser irradiation of adjacent nanowires, and the ions generated by the energy absorbed by the nanowires (ions of the analyte to be analyzed). ) Does not escape smoothly into the vacuum by the physical barrier of the nanowire itself (blocking effect). This prevents a decrease in energy absorption of these adjacent nanowires when they have a length less than or equal to 10 times the average separation distance between the closest nanowires (the separation distance based on the outermost surface of the nanowire), and the generated ions The vacuum escapes smoothly and the ion yield is increased. Furthermore, by satisfying the relation 2, the laser energy is generated in all the nanowires when the laser is irradiated at an angle of 20 to 40 degrees with respect to the vertical direction of the substrate surface while preventing energy loss to the substrate. It is effectively absorbed and the lowering of energy absorption of adjacent nanowires is prevented.

As such, the nanowires satisfy the above relations 1 and 2, and thus have very high desorption / ionization efficiency, very good signal to noise (SNR), and have a very effective molecular weight of 1000 Dalton (Da). You can analyze it.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all of the equivalents or equivalents of the claims as well as the claims to be described later will belong to the scope of the present invention. .

Claims (8)

After placing a sample as a mass spectrometry material on a plurality of nanowires arranged vertically on a substrate and satisfying the following Equation 1 and Equation 2, irradiating a laser to the nanowire where the sample is located and desorption / ionization of the sample Matrix-free mass spectrometry using nanowires to analyze mass.
(Relationship 1)
0.8 x D _pe <D _nw <D _ch
(Relationship 2)
D _ch <L _nw <10xS _nw
(D _nw is the uniaxial diameter of the nanowire, L _nw is the long axis length of the nanowire, the D _ch is the depth of Conductive Heating of the nanowire during laser irradiation, D _pe is nano The penetration depth of laser in the wire, S _nw is the shortest separation distance between nanowires relative to the surface of the nanowires in a plurality of nanowires arranged vertically on the substrate.) The method of claim 1,
The nanowire is a matrix-free mass spectrometry method using nanowires, characterized in that ZnO nanowires. The method of claim 2,
The laser is ultraviolet (UV) light and irradiates the nanowires such that the D _ch is 100 to 150 nm, and the distance S _nw between the closest nanowires of the plurality of nanowires vertically arranged on the substrate is 30 to 36 nm. Satisfying, the nanowire is a matrix-free mass spectrometry method using nanowires, characterized in that the following relations 3 and 4.
(Relationship 3)
45nm <D _nw <55nm
(Relationship 4)
200nm <L _nw <300nm The method according to any one of claims 1 to 3,
A threshold laser power that satisfies a signal to noise ratio (SNR) of 100 during mass analysis by desorption / ionization of the sample is the same material as that of the nanowire, where the mass analysis is performed by replacing the nanowire. The matrix-free mass spectrometry method using nanowires, characterized in that 0.5 to 0.8 times, based on the critical laser power that satisfies the signal to noise ratio (SNR) of 100 of the single crystal substrate. The method according to any one of claims 1 to 3,
The laser is a matrix-free mass spectrometry method using a nanowire, characterized in that irradiated at an angle of 20 to 40 degrees relative to the vertical direction of the surface of the substrate on which a plurality of nanowires are arranged. The method according to any one of claims 1 to 3,
After contacting the nanowires with the analyte solution dissolved or dispersed at a concentration of 100 fmol to 100 pmol in a liquid medium, the liquid medium is removed, to place the sample to be subjected to the mass spectrometry on the nanowires Matrix-free mass spectrometry using nanowires. The method of claim 6,
The contacting method is a matrix-free mass spectrometry method using nanowires, characterized in that the contact is performed by dropping the droplets of the analyte on the nanowires. The method according to any one of claims 1 to 3,
The mass spectrometry target is a matrix-free mass spectrometry method using nanowires, characterized in that having a molecular weight of 200 to 800 Daltons (Da).

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